"In Presenting the Dissertation As a Partial Fulfillment of The

"In presenting the dissertation as a partial fulfillment of the requirements for an advanced degree from the Georgia Institute of Technology, I agree that the Library of the Institution shall make it available for inspection and circulation in accordance with its regulations governing materials of this type. I agree that permission to copy from, or to publish from, this dissertation may be granted by the professor under whose direction it was written, or, in his absence, by the dean of the Graduate Division when such copying or publication is solely for scholarly purposes and does not involve potential financial gain. It is understood that any copying from, or publication of, this dissertation which involves potential financial gain will not be allowed without written permission. THE REACTION OF QUATERNARY AMMONIUM HALIDES WITH SODIUM IN DIOXANE AND IN LIQUID AMNIA

A THESIS

Presented to

the Faculty of the Graduate Division by

Robert William Stevenson

In Partial Fulfillment of the Requirements for the Degree

Doctor of Philosophy in the

School of Chemistry

Georgia Institute of Technology

May, 1958 THE REACTION OF QUATERNARY AMMONIUM HALIDES

WITH SODIUM IN DIOXAME AND IN LIQUID AMMONIA

Approved:

Date Approved by Chairmen:

2 2 I )75-a) ii

ACKNCWIEDGMENTS

The author would like to thank the Research Corporation and the

Rayonier Corporation for fellowships granted to him during the course of this work, and Dean R. L. Sveigert for a Graduate Divisional Fellow- ship. Thanks are also due to Dr. W. M. Spicer for an assistantship, and to Doctor Grovenstein for selecting him to work under the several fellowship grants acknowledged above. The author would like to thank

Doctor Grovenstein for his many suggestions and helpful discussions and his patient guidance of this work to its completion. The author is grateful to his father, William Stevenson, for a loan which enabled the completion of this work without interruption. The patience, understand- ing, and material support of the author's wife during the progress of this work is gratefully acknowledged. •

iii

TABLE OF CONTENTS Page ACKNOWLEDGMENTS ...... 0 0 ......

LIST OF TABLES. . . ...... vi LIST OF ILLUSTRATIONS ...... viii

ABSTRACT. . O 0 0 0 0 0 0 0 0 0 0 ..... 0 0 0 0 ix Chapter

I. INTRODUCTION . • ...... 1 II. REAGENTS AND SOLVENTS USED, WITH METHODS OF PURIFICATION . 8 III. PREPARATION OF AMINES AND QUATERNARY AMMONIUM SALTS. . . 13 Preparation of Quaternary Ammonium Halides Tetra-n-butylammonium Bromide Tri-n-butylmethylammonium Bromide Tri-n-butylmethylammonium Iodide Di-n-butyldimethylammonium Bromide Di-n-butyldimethylammonium Iodide n-Butyltrimethylammonium Chloride n-Butyltrimethylammonium Bromide n-ButyltrimethylNmmonium Iodide sec-Butyltrimethylammonium Iodide t-Butyltrimethylarnmonitmr Iodide Tetra-n-propylammonium Bromide Tri-n-propylmethylammonium Bromide n-Propyltrimethylammonium Iodide Isopropyltrimethylammonium Iodide Isapropyltrinethylammonium Bromide Triethylmethylammonium Iodide Triethylmethylammonium Bromide Triethylmethylammonium Chloride Ethyltrimethylammonium Bromide Ethyltrimethylemmonium Iodide Tetramethylammonium Bromide Chloromethyltrimethylammonium Chloride Chloromethyltrimethylammonium Bromide 2-Chloroethyltrimethylammonium Chloride 5-Chloroamyltrimethylammonium Chloride Chloromethyldimethylbenzylammonium Bromide iv

Chapter Page Preparation of Amines Di-n-butylmethylamine Dimethyl-sec-butyImmine Dimethyl-t-butylmmine Dimethylisopropylamine Purity of Compounds Halogen Analyses Melting Points Derivatives Neutralization Equivalents Crystallization

IV. ANALYSIS OF PRODUCTS ...... . . . e ..... 42 Analytical Techniques Validity of Analytical Techniques

V. DESCRIPTION OF APPARATUS AND TECHNIQUES. . 65 Reactions with Sodium in Dioxane Reactions with Sodium in Liquid Ammonia VI. REACTIONS OF TETRAALKYLAMMONIUM HALIDES WITH SODIUM IN DIOXANE 73 Reactions of Tetraalkylammonium Halides with Sodium in Dioxane-t-amyl Alcohol Mixtures Reaction of t-Amyl Alcohol with Sodium in Dioxane The Reaction of t-Butyl Methyl Ether with Alkali Metals Reactions of Tetraalkylammonium Halides with Sodium in Dioxane The Reaction of t-Butyltrimethylammonium Iodide with Sodium in Cumene Side Reactions The Reaction of Tetra-n-butylammonium Bromide with Sodium in Dioxane The Reaction of Tetraethylammonium Bromide with Sodium in Dioxane The Reaction of Tetramethylammonium Bromide with Sodium in Dioxane VII. THE REACTION OF TETRAAIKMADMONIUM HALIDES WITH SODIUM IN LIQUID AMMONIA . . • ...... 106 Chapter Page

VIII. REACTIONS OF OMEGA-CHLOROALKYLTRIMETHILAMMONIUM HALIDES WITH SODIUM . . . 118

The Reaction of 5 -C hloroamyltrimethylanmionium Chloride with Sodium in Dioxane The Reaction of 2-Chloroethyltrimethylammonium Chloride with Sodium and with Zinc Dust

The Reaction of Chloromethyltrimethylammonium Bromide with Sodium IX. TESTS OF STABILITY OF PRODUCTS AND SOLVENT UNDER REACTION CONDITIONS . . 0 o e o e o o e e o 0 0 0 0 0 0 0 0 0 0 o e e 139 X. EVALUATION AND DISCUSSION OF THE REACTIONS OF TETRA ALKYL- AMMONIUM HALIDES WITH SODIUM. . 0 o e e e o 0 o e e o e . . 146 Relative Cleavage Rates of Alkyl Carbanions Relative Cleavage Rates of Alkyl Free Radicals Discussion of Results

XI. EVALUATION AND DISCUSSION OF THE RESULTS OF THE REACTIONS OF OMEGA-CHLOROALKILTRIMELULAMMONIUM HALIDES WITH SODIUM . 188 The Reaction of Cbloromethyltrimethylammonium Bromide with Sodium The Reaction of 2-Chloroethyltrimethylammonium Chloride with Zinc Dust and with Sodium-t-amyl Oxide The Reaction of 5-Chloroamyltrimethylammonium Chloride with Sodium in Dioxane

Comparison of Reactions Carried Out by Gordon on omega- Ch1oroa1kyltrimethylammonium Halides with the Analogous Tetraalkylammonium Salts

XII. CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK . e o e e . 198

LITERATURE CITED e e e e e e e e e e e e e o e a e e e e e e e e e 205

VITA . . op0000•op00000 000•Ooo 212 o• o • *. vi

LIST OF TABLES

Table Page 1. Results of Ionic Halogen Analyses 34

2. Melting Points of Quaternary Ammonium Halides and Picrates 39 3. Linearity of Partial Pressure vs. Optical Density Plots of Various Hydrocarbons 59 4. Analyses of Synthetic Methane-Alkane Mixtures 60

5, Apparent Results of Reaction of n-Butyltrimethylammonium Chloride with Sodium in Dioxane-t-Amyl Alcohol 74

6. Results of Reactions of Tetraalkylammonium Halides with Sodium in Dioxane (PreliminAry Runs) 93 7. Results of Reactions of Tetraalkylammonium Halides with Sodium in Dioxane 94

8. Alkene Product Yields from the Reactions of Quaternary Ammonium Halides with Sodium in Dioxane . . . ..... 102 9. Products from Reaction of Tetraalkylammonium Halides with Sodium in Liquid Ammonia According to Preliminary Procedures 107

10. Results of Reactions of Tetraalkylammonium Halides with Sodium in Liquid Ammonia, Technique 2 ...... . . 108

11. Products from Reactions of Tetraalkylammonium Halides with Sodium in Liquid Ammonia, Technique 1 110 12. Products from Reactions of Symmetrically Substituted Quaternary Ammonium Halides with Sodium in Liquid Ammonia 115 13. Results of Reaction of 2-Chloroethyltrimethylammonium Chloride with Zinc Dust in Aqueous Ethanol. . ...... 128

14. The Reaction of Chloromethyltrimethylammonium Bromide with Sodium in Dioxane. . . . < . 133 15. Average Methane to Alkane Ratios Derived from Reactions of Quaternary Ammonium Halides with Sodium. . . . . 158 vii

Table Page

16. Comparison of Found Alkane to Methane Ratios with Those Predicted on the Basis of Both Steric Effects and a Carbanion Mechanism 161

viii

LIST OF ILLUSTRATIONS

Figure Page 1. Partial Pressure of Hydrocarbons vs. Optical Density near 6.8 Microns ...... . . . . . 57 2. Partial Pressure Alkene vs. Optical Density 58

3. Partial Pressure (mm.) of Methane at 25® vs. Optical Density at 7.69 Microns and Effect of Added Hydrocarbons on Methane Optical Density. . . 63

4. Schematic Diagram of the System Used for Reactions with Sodium in Liquid Ammonia 69

5. Comparison of Methane to Aikane Ratios from Cleavage of Quaternary Ammonium Salts in Liquid Ammonia with Those in Dioxane 170 ix

ABSTRACT

This thesis was undertaken to ascertain the relative ability of saturated alkyl groups to cleave from quaternary nitrogen on reaction with sodium by the overall reaction

R4NX + 2Na 4- BE RE NaX BNa f R3N and thereby to determine whether the cleavage proceeded through the initial formation of free radicals or of carbanions. BE is any entity of the reaction mixture capable of donating a proton to an intermediate carbanion. A second purpose was to gain information about the products of the reactions of chloromethyltrimethylammonium bromide and of 5- chloromyltrimethylammonium chloride with sodium, and to draw relevant conclusions concerning the mechanisms of these reactions, which may proceed by way of the zwitterion (CV 2IN(CH3 )3 . A third purpose was to show whether or not the abstraction of the beta-chlorine from 2-chloroethyltrimethylammonium chloride by active metals was a concerted reaction to give ethylene and trimethylamine, strictly analogous to an ordinary beta-elimination reaction.

The hydrocarbon products of the reactions were determined qualitatively and frequently quantitatively by infrared analytical techniques.

Classical chemical absorption techniques were generally employed for the quantitative determination of total unsaturates. The particular infrared techniques used in this work were thoroughly checked and their validity empirically demonstrated. x

Tetraelkylammonium salts bearing only unsubstituted alkyl groups of the type ARCH3 )4_113X gave methane (when methyl groups were present), --n an alkane corresponding to the higher alkyl substituent, and an alkene_ formed by a Hofmann elimination reaction which competed with the reductive cleavage. When methyl substituents were present, ethylene was usually observed among the hydrocarbon products, The formation of ethylene is attributed to intermolecular methylation and subsequent elimination. After correction for statistical factors, the following relative rates of reductive cleavage of alkyl groups were found in liquid ammonia (CH3 is assigned a relative rate of 100): t-C411 9,

87,600 + 20,200; CH3, 100; sec-C4H9, 41.6 + 2.9; i-C 3H7 , 13.6 + 0.7; n-C3H7 , 1.7 + 0.1; n-C4119, 0.84 + 0.06; C2H5 , 0.82 + 0.05. In dioxane the order was: t-C4119, 10,750 + 810; CH3 , 100; sec-C4119, 50.6 + 1.8;

1-C3H7, 29.0 + 1.4; C2115 , 4.2 + 0.1; n-C3117, 2.4 + 0.1; n-C4H9, 2.4 +

0.1. The results are interpreted as indicating that secondary and tertiary alkyl groups cleave by a free radical mechanism and methyl groups by a earbanion mechanism. The mechanism of cleavage of normal alkyl groups was assigned a carbanion mechanism on the basis of permissive evidence.

The qualitative results in liquid ammonia and in dioxane were similar. Greater selectivity was found for cleavage of alkyl groups in boiling liquid ammonia (-33 ° ) than in boiling dioxane (101.8 (3 ). This effect is attributed to the large difference in boiling point of the two solvents. In liquid ammonia, the methane to alkane ratios from tri-n- butylmethylammonium bromide and sec-butyltrimethylammonium iodide were xi

shown to be higher when the reactions were carried out in liquid ammonia at dry ice temperature than when they were carried out at the boiling point of liquid ammonia.

The methane to butane ratio (statistically corrected to equal numbers of groups) was shown to increase with increasing number of butyl groups; the methane to butane ratios for the following salts reacted with sodium in liquid ammonia area n-butyltrimethylammonium bromide, 92.3 + _

10.3; di-n-butyldimethylammonium bromide, 112.5 + 5.0; tri-n-butylmethylammonium bromide, 139.5 + 3.3. The increase in ratio cap be correlated with the stabilities of the amines formed in the cleavage reaction, or it could be attributed to a steric influence in the formation of the transition state complex. The methane to alkane ratio was found to increase somewhat with the anion, from chloride to bromide to iodide, on reaction of the salt of a given cation with sodium in dioxane. The increase was rationalized on the basis of the involvement of ion pairs

(most extensive for chloride) in the cleavage reaction, with a consequent partial shielding of methyl groups from cleavage.

Kinetic studies are recommended on some of the salts, particularly t-butyltrimethylammonium iodide with sodium in liquid ammonia, whereby the free radical or carbanion nature of the reaction might be more conclusively demonstrated. Study of the possible variation of methane to isobutane ratio with sodium concentration is suggested as an alternate approach.

Chloromethyltrimethylammonium bromide on reaction with sodium in dioxane gave for a typical run ethylene (37.5 per cent), methane (12.2 per cent), ethyldimethylamine (19.5 per cent minimum, 26.5 per cent xii

maximum), trimethylamine (by difference, 42.7 per cent), and, in some cases, traces of vinyldimethylamine. The ethylene could have arisen by any of three mechanisms; a mechanism of intermolecular alkylation with subsequent elimination is preferred. The ethyldimethylamine is probably in part a cleavage product of ethyltrimethylammonium ion formed by intermolecular alkylation. The yields of methane and ethyldimethylamine in some of the runs, however, indicate that some of the ethyldimethylamine must be formed intramolecularly, probably by a Stevens rearrangement. Other intramolecular rearrangement mechanisms are alpha elimination and gamma elimination. The latter two mechanisms require base catalysis. The methane probably arises from a reductive cleavage reaction of the type discussed above. Labeling of the salt with radioactive carbon in the chloromethyl group is recommended as a means of gaining further information about the reaction.

2-Chloroethyltrimethylammonium chloride was reacted with zinc dust in aqueous ethanol to give ethylene (60.4 per cent), trimethylamine

(52.0 per cent), and an organic salt (3.5 grams from 0.089 mole 2- chloroethyltrimethylammonium chloride) which gave only acetylene on

Hofmann degradation. It was concluded that abstraction of a beta- chlorine and the formation of ethylene from the salt were concerted, as expected by analogy with an ordinary beta-elimination reaction.

On reaction with sodium in dioxane, 5-chloroamyltrimethylammonium chloride gave pentene-1 (29.7 per cent), methane (39.6 per cent), trimethylamine (40.3 per cent), n-amyldimethylamine (29.1 per cent), n- pentenyldimethylamine (8.8 per cent), a small yield of ethylene, and traces of an amine bearing ethyl substituents (0.2-0.3 per cent) Except for the n-pentenyldimethylamine, the products of the reaction are qualitatively and semi-quantitatively analogous to those from the reaction of n-butyltrimethylammonium chloride with sodium in dioxane. The reaction is most suitably described, therefore, as proceeding by intermediate formation of n-amyltrimethylammonium chloride. The n-amyltrimethylammonium ion arises by abstraction of a proton by the zwitterion,

CH2CH2CH2CH2CHN(CH3 ) 3 , from the dioxane. Dioxane must be a good proton donor to carbanions, since most tetraalkylammonium halides react rapidly with sodium therein to give alkanes. It is recommended that salts of the type Cl(CH2) nN(C113 )3X where n = 3 to 5 be further studied in solvents of lesser proton donating ability in order that intramolecular reactions of the zwitterion CH2 (CH2) n _ 1 W(03)3 might be observed in a more nearly unequivocal manner.

CHAPTER 1

INTRODUCTION TO PROBLEM

Reaction of tetraalkylmmonium halides with sodium.--Recently it has

become known that simple alkyl groups may be reductively cleaved from

quaternary nitrogen by reaction with sodium under appropriate condi-

tions. 12 2 The overall reductive cleavage of a tetraalkylammonium halide

(R OX) with sodium may be written:

RIF + 2Na + BH RH + R3N + Biqa + NaX

where BH represents any entity in the reaction mixture capable of

donating a proton.

Two reasonable mechanisms have been suggested 1 for the reductive

cleavage reaction, the carbanion mechanism and the free radical mechanism.

The carbanion mechanism may be written:

R4Nx 21(41 slow> R- + R311 + 2Na+ +

+ BEI re RH +

and the free radical mechanism may be written:

ROIX + Na Flo` R N + NaX 3

1D. A. Gordon, Unpublished Ph. D. Thesis, Georgia Institute of Technology, 1953.

2W. L. Jolly, J. Am, Chem. Soc., ly, 4958 (1955).

II° Na fast R- + Na+

R + BH fast > RH + B

Arguments against a third mechanism involving dissociation of a tetra-

alkylammonium halide to tertiary amine and alkyl halide followed by

reaction of the alkyl halide with sodium

R4NX + RX

RX + 2Na RNa + NaX

RNa + BE ---•-- RH + BNa

have been presented by Gordon.'

In this study an attempt was made to distinguish between the free

radical and carbanion mechanisms of reductive cleavage on the basis of

the ease of cleavage of groups under two sets of reaction conditions--

namely with molten, finely divided sodium in dioxane and with solutions

of sodium in liquid ammonia. Thus in the reaction of di-n-butyldimethyl- i ammonium bromide, where methyl and butyl groups compete for cleavage on

an equal statistical basis, more butane than methane is expected if the

free radical mechanism prevails, since an n-butyl free radical is more

stable than a methyl free radical. If, however, the carbanion mechanism

prevails more methane than butane is expected since methyl carbanions are

more stable than n-butyl carbanions.

The objectives of the present study were as follows: to determine

the effect of structure of alkyl groups on relative amounts of methane

and higher alkane evolved; to determine the effect (if any) of changing

halide anion on the relative amounts of methane and higher alkane

evolved; to determine the effect of cation structure (for example, 3

di-n-butyldimethylammonium bromide vs. tri-n-butyImethylammonium bromide)

on the statistically corrected methane to alkane ratio; and to determine

what change in the preceding three factors is occasioned on changing from the homogeneous liquid ammonia medium to the heterogeneous dioxane medium,

which was also at a higher temperature. The data collected to meet these objectives also comprise a

potentially useful extension of the EWde degradation, which has frequently been used in studies of natural products. The classical Erode conditions employ sodium amalgam in aqueous medium3 to effect the reductive cleavage of quaternary ammonium salts. Under such conditions only unsaturated

groups such as benzyl and allyl cleave with ease. Gordon succeeded in cleaving allyltrimethylammonium chloride to propylene and trimetbylamine

and tetramethylammonium chloride to methane and trimethylamine (besides a

little ethylene) by use of sodium in refluxing dioxane with high speed stirring. 1 Blanchard studied the reactions of tetramethylammonium chloride, n-butyltrimethylammonium chloride, di-n-butyldimethylammonium chloride, tri-n-butylmethylammonium bromide, trim-butylmethylammonium iodide, and tetra-n-butylammonium bromide with molten sodium in dioxane-t-amyl alcohol mixtures. 4 Although an impurity of t-amyl alcohol gave rise to a product interfering with the butane analyses, a he was able to show that methane was preferentially cleaved in each case.

alvidence for this will be presented below. 3H. Erode, Arch, Pharm., 244, 289 (1906). E0 P. Blanchard, Unpublished M. S. Thesis, Georgia Institute of Technology, 1954. While this work was in progress, Jolly2 reacted tetraethylammonium

bromide with sodium in liquid ammonia to produce ethane and ethylene. Hazlehurst 5 and coworkers have reacted tetraethylammonium chloride with

potassium in liquid ammonia at -78° to obtain ethane and ethylene; tetramethylammonium iodide, bromide, and chloride to produce methane and

traces of ethylene; tetra-n-propylammopium halide to obtain propane and propylene; triethylmethylammonium halide to obtain methane, ethylene, and

a trace of ethane; tri-n-propylmethylammonium halide to obtain methane, propylene, and a trace of propane.

Thompson and Cundall 6 in 1888 reported that tetramethylammonium

iodide when reacted with potassium in liquid ammonia at room temperature

gives ethane, trimethylamine, and potassium iodide. Schlubach and Ballauf7 have reacted tetraethylammonium chloride

with potassium in liquid ammonia to obtain triethylamine. They assumed the reaction:

2K + 2(C2)4NC1 a 2ECl + C4H10 + 2(C2H5)3N

They obtained more gas than was predicted by this equation, however. Sugasawa and Matsuo8 have found that an Emde type degradation of benzyltrimethylammonium chloride to toluene and trimethylamine may be accomplished using Raney nickel in water at room temperature.

5D. A. Hazlehurst, A. K. Holliday, and G. Pass, J. Chem. Soc., 4653 (1956). 6C. M. Thompson and J. T. Cundall, J. Chem. Soc., 22, 761 (1888). 7H. H. Schlubach and F. Ballauf, Ber. 2 .11„ 2811 (1921). 8S. Sugasawa and H. Matsuo, J. Pharm. Soc. Japan 4, 142 (1956). 5

Birch9 has succeeded in cleaving phenyltrimethylammonium iodide to benzene in 51 per cent yield by use of solutions of sodium in liquid ammonia to which t-amyl alcohol had been added. Phegyltrimethylammoniwn iodide is reduced only with great difficulty under the usual Emde conditions. 1° Further examples and references to the Bade degradation are to be found in References 1 and 4. The reaction of chloramethyltrimethylammonium bromide with sodium.--The reaction of chloromethyltrimetbylammonium bromide with finely divided molten sodium in dioxane would be expected to give initially a zwitterionl

with the reactions of alkyl chlorides with sodium. by analogy

- + C1CH2N(CH3)3 + 2Na —0- 2Na+ + Cl- + CH2N (CH3)3

Wittig11 ' 12 has been investigating this zwitterion rather extensively. On treating tetramethylammonium bromide with phenyllithium, he reported a 20 per cent yield of polymetbylene and trimethylamine, in + + +- + addition to greater yields of LiCH2N(CR 3 ) 3 and (LiCR2) 2N(CR3 ) 2 . Both of the metalated quaternary ammonium ions gave addition products with benzophenone. Since a lithium to carbon bond has some covalent character, it might be expected that Wittig's zwitterion would be stable enough to permit derivatives being prepared. The present work, however, gave rise

9A, J. Birch, J. Proc. Roy. Soc. N. S. Wales, 81 21 (1949)•

10R. Fade, Arch. Pharm., 2E,1 369 (1909). 11G. Wittig, Angew. Chemie, 66, 14 (1950. 12G. Wittig, Angew, Chemie, 63, 15 (1951). 6

to the zwitterion under conditions such that the charged carbon atom was of highly ionic character and therefore further reactions might be expected to occur. An objective of this study was to gain as much information as possible about the mechanism(s) of the reaction of chloromethyltrimethylammonium bromide with sodium through a study of the products. Earlier studies on this reaction have been carried out by Blanchard4 who reported ethyldimethylamiae, vinyldimethylamine, and trimethylamine as the only products. The reaction of 2-chloroethyltrimethylammonium chloride and of 2L chloroamyltrimethylammionium chloride with sodium.--The purpose of studying the reactions of the salts 2-chlaroethyltrimethylammonium chloride and 5-chloroamyltrimethylammonium chloride with sodium was to gain further information as to the reactions of amega-chloroalkyltrimethylammonium halides with sodium, and to determine whether the reaction of 2-chloroethyltrimethylammoniam chloride with sodium is truly concerted.

The reactions of omega-chloroalkyltrimethylaamionium halides from 2-chloroethyl through 4-chlorobutyl have been studied by Gordon.' In addition to the mechanisms he sets forth, the following mechanism may be considered, using the zwitterion derived from 4-chlorobutyltrimethyl- ammomium ion as a typical case

H2 -C1112\71.- ,...--cH2-CH2 4. 1 ‘ CH2 TH3)2 -4. CH2 ..›CH3)2 ------10- ..*--- CH2-H-CE2 ------CH3 CH2 CH3CH2CHT=CB2 + (CH3 ) 3N

The second step of the mechanism here postulated has been suggested by 7

CV 1 Wittig, who has observed that salts of the type RCH2CH24-f-CH2X X when 6H3 13 treated with phenyllithium gave an olefin RCH=CH 2 and trimethylamine.

The first step has been suggested by Gordon. 1

13G. Wittig and R. Poister, Ann. 599, 13 (1956 ). 8

CHAPTER II

REAGENTS AND SOLVENTS USED, WITH METHODS OF PURIFICATION

Acetone.--Commercial grade acetone was dried over MgSO4.

Ammonia.--Matheson Company, Inc. anhydrous ammonia (99.9 per cent minimum purity) was condensed in the reaction vessel in which it was to be used. t-Amyl alcohol.--Matheson, Coleman, and Bell t-amyl alcohol was refluxed

over sodium for six hours and distilled, at b, p. 101.5 - 102.0 ° at local

atmospheric pressure (ca. 740 mm.). n-Butane. --Matheson instrument grade butane (99.0 per cent minimum purity) was used without further purification. Butene-1.--Matheson C. P. grade was used without further purification. t-Butyl alcohol.--Eastman Kodak white label and Matheson Company, Inc.

grade t-butyl.alcohol was refluxed over sodium overnight and distilled from sodium at b. p. 81.2 - 81.8° at 732 mm. t-Butylamine.--Matheson„ Coleman, and Bell t-butylamine was distilled through a four-feet long glass helix packed column at b. p. 43.7 0 at

744 mm. n-Butyl bromide.--Bastman white label grade was distilled through a six-

feet glass helix packed glass column, at b, p. 98.2 ° at local atmospheric

pressure (about 740 mm.).

n-Butyl chloride.--Eastman white label grade was distilled through a

six-feet glass helix packed column at b, p. 76.5 - 77.1 ° at local

atmospheric pressure (about 740 mm.). 9

n-Butyl iodide.--Eastman white label grade was distilled through a one-

foot vacuum jacketed column packed with helices at b. p. 127.8 ° at 711.11. mm. t-Butyl methyl ether.--Eastman white label grade was distilled at b. p. 52 - 53.5° at 745 mm.

Choline chloride.--Eastman white label grade was dried in a vacuum desiccator and used without further purification.

Methylene chlorobramide.--Eastman white label grade, distilled by Blanchard, was used. 14

Cumene.--Eastman yellow label cumene from stock was purified according 15 to the method of Vogel. One thousand grams of cumene was shaken thoroughly with eleven 100 ml. portions of concentrated sulfuric acid, then washed with water, 10 per cent Na2CO3 solution, and water. It was then refluxed over sodium with high speed stirring for two hours vnaer nitrogen, and distilled. The forerun had b. p. of 112.3 - 48.1 ° at

738.7 mm, and amounted to seven per cent of the starting material. The main fraction had b. p. of 148.1 - 149 ° at 738.7 mm. or 153.0 - 153.9 °

corrected to 760 mm. The product was stored under nitrogen in a brown glass bottle over sodium wire.

Di-n-butylamine.--Eastman white label grade was distilled through a six- feet column packed with glass helices and had b. p. 154.2 - 155.1° at

742 mm.

15-Dichlorope.--Eastman white label grade was distilled through a three-feet long glass packed column at b. p. 77.2 - 78.1 ° at 21.0 -

21,9 mm.

14E. P. Blanchard, Unpublished M. S. Thesis, Georgia Institute of Technology, 1954, p. 16.

15A. I. Vogel, J. Chem. Soc., 607 (1948). 10

Columbia Organic Chemicals grade was distilled through a one-foot

long glass packed column at b. p. 76.0 - 79.8° at 20.7 - 22.5 11M4 N,N-Dimethylbenzylamine.--Eastman white label grade was distilled at

b. /) 173° uncorrected or b, p. 181 ° corrected to 760 mm. Diethyl ether.--Merck anhydrous reagent ether was stored over sodium wire in brown glass screw cap bottles.

1 24.42.----Matheson, Coleman, and Bell grade, after purification according to the method of Fieser, 16 had b, p. of 100.2° at 745.1 mm. and was stored in brown screw cap bottles over sodium wire.

Ethane.--Phillips Research Grade (99.75 per cent typical lot purity) was used without further purification. Ethanol.--Commercial absolute ethanol was purified according to the method of Fieser. 16 ELky1 bromide.--Eastman white label grade was distilled at b. p. 37.1 - 37.4° at 740 mm. Ethyl iodide.--Matheson, Coleman, and Bell grade was used without further purification.

Formalin.--Baker's PriPlyzed reagent grade 37 per cent formaldehyde solution was used without further purification. Formic acid.--Eastman Organic Chemicals white label 98 per cent grade was used; technical grade from stock was also used.

Isobutane.--Matheson instrument grade (99.5 per cent minimum purity) was used without further purification.

IscrpLoa.---Commereial isopropanol was refluxed over quicklime for 27 hours and distilled at b. p. 80.2 - 81.0 ° at 743 mm.

1, F. Fieser, Experiments in Or is Chemistry, Third Edition, D. C. Heath and Company, Boston, 1955, p. 2°5. 11

Isopropylamine.--Eastman white label grade was distilled at b. p. 31.8 -

32.5° at 742 mm.

Methane.--Phillips Research Grade (typical purity, 99.62 per cent) was used without further purification.

Mathanol.--Commercial grade was refluxed over magnesium turnings (5 g.

Mg/l. methanol) for three hours and distilled at b. p. 64 ° at local atmospheric pressure (about 740 mm.).

Methyl bromide.--Matheson Company, Inc. grade (99.4 per cent minimum purity) was used.

Methyl chloride.--Matheson Company, Inc. grade (99,5 per cent minimum purity) was used.

Methyl iodide, 'Baker analyzed grade was used without further purifica- t ion.

Methyl ethyl ketone.--Matheson Company, Inc. grade was dried over IWO4.

Phenyl isocyanate.--Eastman white label grade was used from stock without purification.

Propane.--Matheson Company, Inc. grade was used without further purifica- t ion. n-Propyl bromide.--n-Propyl bromide from stock was distilled at b. p.

68.0 - 69.0° at 745 mm. n-Propyl iodide.--Eastman white label grade was distilled. There was a cloudy forerun, b. p. 83 - 98.5°, a yellow fraction, b. p. 98.9 - 99.1 °, o and a main fraction, b. p. 99.1 at 737 mm.

Tetryltumnonium bromide.--Eastman white label grade was used without further purification. 12

Thionyl chloride.--Eastman white label grade was purified by the method of Cattle17 according to the following procedure: Five hundred grams of thioiy1 chloride was refluxed for four hours with nine grams of sulfur. The material was distilled through a glass helix packed column three feet long, with removal of a yellow forerun. The material was distilled nearly to dryness, then redistilled through a foot long glass-packed column to give a main fraction of b, p. 75.2° at local atmospheric pressure.

Trimethylamine.--Eastman white label 25% trimethylamine in methanol was used without further purification. ilr amine.---Es.Ertman white label grade was distilled. Nine hundred milliliters boiling at 207.5 - 209.5° at 744 mm. was collected. Triethylamine.--Eastman white label grade was distilled; b. p. of main fraction was 88010 at 739 mm., 88.9° •corrected to 760 mm. Tri-n-propylamine.--Eastman white label grade was distilled; b. p. was

149 - 152.1° uncorrected at 745 mm. Tetrahydrofuran.--Two liters of Matheson grade tetrahydrofuran were heated to reflux with 36 grams of potassium in a three liter Morton flask and subjected to high speed stirring for one hour. The material was then distilled to give a main fraction of b. p. 66 ° at 748.8 mm. A nitrogen atmosphere was maintained throughout the purification.

17D. L. Cattle, J. Am. Chem, Soc. 68 1380 (1946). 13

CHAPTER III

PREPARATION OF AMINES AND QUATERNARY AMMONIUM SALTS

Preparation of Quaternary Ammonium Halides Tetra-n-butylammonium bromide.--The salt prepared by Blanchard was used. 18

L.1 .._-11.-1DutilmetAy_Iammoniumbromide.--The salt prepared by Blanchard was

used. 19 A further preparation was made as follows: Acetone (250 ml.) was

chilled in an ice bath and 94 g. (0.99 mole) of methyl bromide was dissolved in the acetone. To this solution was added 148 mi. (0.62 mole)

of tri-n-butylamine. After four hours at ice-bath temperature, the re-

action flask was allowed to stand at room temperature overnight. The contents of the flask were then poured into 550 ml. of dry ether, whereupon a white turbidity appeared. After a day in the refrigerator most

of the ether was decanted. Seven hundred milliliters of fresh, dry ether was added and the flask was returned to the refrigerator. One day later the salt was filtered with suction and washed with dry ether. The yield of salt was 87 per cent based on amine taken. The halide analysis indicated a product of high purity requiring no recrystalliza-

tion.

Tri-n-butylmethylammonium iodide.--The salt prepared by Blanchard was

used. 19

18E. P. Blanchard, op. cit., pp. 22, 23.

19Ibid., p. 250 14.

Dis-butldimenonium bromide.--Acetone (350 ml.) was chilled in a dry ice-acetone bath and 119 g. (1.25 moles) of methyl bromide was dissolved in the acetone. To the chilled mixture was added 80.0 g. (0.56 mole) of di-n-butylmethylamine. The reaction flask was removed to the air. When crystals appeared, the flask was returned to the dry ice bath to moderate the reaction. The flask was alternately placed in the bath and removed to room temperature until the reaction appeared complete.

Two hundred milliliters of dry ether was added to the flask. After three days storage in the refrigerator, the salt was filtered with suction and dried in the vacuum oven at 60° . The yield was 95 per cent based on the amine taken.

Di-n-butyldimethylammonium iodide.--A mixture consisting of 500 ml. of methyl ethyl ketone and 110 g. (0.77 mole) of di-n-butylmethylamine was chilled in a dry ice-acetone bath. To this mixture was added 75 ml. (1.20 moles) of methyl iodide. The flask was stoppered and was allowed to remain in the bath overnight. At the end of this time there was an almost transparent solid mass in the bottom of the flask. The stopper was loosened and the flask set out at room temperature. The crystalline cake in the bottom of the flask was broken up and 100 ml. of dry ether was added. The flask was stoppered and stored in the refrigerator for three days, after which the salt was filtered and washed with dry ether.

The crude yield of fluffy, white, needle-like crystals was 98 per cent. Satisfactory halide analyses were not obtained on this material, either before or after recrystallization from t-butyl alcohol. The yield of recrystallized material was 75 per cent. 15

n-BlimylammoniumataJ.tr chloride.--The salt prepared by Blanchard was used. 20 Additional salt was prepared by mixing 104 ml. (1.0 mole) of n-butyl chloride with 1.0 mole of trimethylamine in methanol (335 ml. of 25 per cent trimethylamine in methanol). After 144 days at room temperature, the solvent was evaporated with the aid of a stream of nitrogen and heating After cooling, dry ether was added and the mixture stored in the refrigerator. Three weeks later the ether was decanted and fresh, dry ether added. The material was filtered with suction and dried in the vacuum oven at 800 . The yield of salt was 72 per cent. Halide analyses indicated that recrystallization was not necessary. n-Butltrim um bromide.--To 335 ml. of 3.0 N methanolic trimethylamine solution in a flask surrounded by dry ice was added 107 ml.

(1.0 mole) of n-butyl bromide. The flask was then removed from the dry ice and stored at room temperature. After nine days, titration of an aliquot of the flask contents with standard hydrochloric acid indicated that the reaction was complete. The solvent was evaporated with the aid of a stream of nitrogen and heating until solid material appeared.

After cooling , dry ether was added. Seven days later the ether was decanted and fresh, dry ether added. The salt was not quite completely crystalline at this point. Four days later the salt was filtered with suction and dried in the vacuum oven at 6o0 . The yield was 87 per cent.

iodide.--To 1.0 mole of trimethylamine in 335 ml. of methanol (335 mi. of methanolic trimethylamine which contained

25 per cent trimethylamine) which had been chilled in a dry ice bath was

2 °Ibid., p. 18. • 16 added 115 ml. (1.0 mole) of n-butyl iodide. The reaction flask was then removed from the dry ice and stored in the refrigerator for 31 days and then at room temperature for 20 days. Eydrochloric acid (1.25 ml. of

0.1534 N acid) was required for neutralization of one milliliter of the reaction mixture both at the beginning and at the end of the 20 day period, and the reaction was assumed to be complete. The volume of solvent was reduced by heating the mixture while passing a stream of dry nitrogen through it. The mixture was cooled, during which time some material crystallized. Additional material was thrown down by addition of dry ether. After two weeks standing, the material was filtered with suction. The yield of salt was 82 per cent. The ionic halogen analyses indicated that no recrystallization was necessary. sec-Butyltrimethylammonium iodide.-eA solution of 38.5 g. (0.38 mole) of dimethyl-sec-butylamine in 250 ml. of methanol was chilled in a dry ice bath. To this solution was added 25 ml. (0.41 mole) of methyl iodide. The reaction flask was removed from the dry ice bath and stored in the refrigerator for six days. Fifty milliliters of dry ether was added, giving rise to a transitory white precipitate. An excess (0.41 mole) of methyl iodide was then added. The reaction was found to be complete after eight more days by titration of an aliquot of the flask contents with stendard hydrochloric acid. The contents of the flask were transferred to a distilling flask and most of the solvent distilled. The hot residue was transferred to an Erlenmeyer flask and cooled. The addition of 25 ml. of dry ether led to the precipitation of a white sludge.

Nineteen days later, a good crop of needle-like crystals was found at 17 the bottom of the flask. The crystals were isolated by means of suction filtration and dried in the vacuum oven for five hours at a maximum temperature of 50° . The yield of salt was 82 per cent based on amine taken. A second crop of material, a crystalline powder, was isolated from the combined filtrate and dry ether washings of the first crop. An additional yield of 15 per cent was thus obtained, making the total yield of salt 97 per cent based on the amine taken. Ionic halogen analyses indicated that recrystallization was not required. t-Butraetloammnium iodide.--To chilled methanol in a ground glass stopper Erlenmeyer flask were added 37 ml. (0.59 mole) of methyl iodide and 53.5 g. (0.56 mole) of dimethyl-t-butylamine. A vigorous reaction occurred, causing the solution to bubble somewhat. The flask was placed in a dry ice-acetone bath and shaken to moderate the reaction. A flock of fine white crystals precipitated. The flask was removed from the bath and stored in the refrigerator for 24 hours. After five days at room temperature, the salt was isolated by suction filtration. The salt was dried in the vacuum oven for 36 hours at 82 0 . Ionic halogen analyses indicated that no recrystallization was necessary. The yield of salt was

99 per cent. TeLEA:EtplmaAngaIs bromide.--To 35 ml, of methyl ethyl ketone were added 28.4 ml. (0.15 mole) of tri-n-propylamine and 14.4 ml. (0.16 mole) of n-propyl bromide. After four days at room temperature, titration of an aliquot of the reaction mixture with standard hydrochloric acid indicated only 6.7 per cent reaction. The reaction flask was fitted with a reflux condenser protected by a Drierite-filled drying tube, and 18

the mixture was refluxed on a steam bath for 48 hours. After 16 hours at roam temperature, the crystals were filtered off with suction. There was still some unreacted amine, as indicated by its odor. The yield of salt was 1.6 per cent. Ionic halogen analyses indicated that there was no need for recrystallization.

iodide.--Two hundred milliliters of methyl ethyl ketone in a groura glass stoppered Erlenmeyer flask was chilled in an ice bath. Tri-n-propylamine, 86 ml., (0.46 mole) and 35 ml. (0.56 mole) of methyl iodide were added to the flask. The reactants were kept in the ice bath for one hour and at room temperature for one hour. The salt was isolated by suction filtration. Some material which precipitated in the filtrate was not recovered, but the yield of salt isolated was 82 per cent. Satisfactory halide analyses were not obtained for this salt. n-Propyltrimethylammonium iodide.--To 306 ml. of 25 per cent trimethylamine in methanol (containing 0.92 mole trimethylamine) which had been chilled in a dry ice-acetone bath was added 100 ml, (1.03 moles) of n-propyl iodide. The flask was removed from the dry ice bath and stored in the refrigerator. After five days, the flask was chilled in a dry ice bath, the supernatant liquid poured off, and about 900 ml. of dry ether added. The salt was then isolated by suction filtration and dried on the filter. The yield of salt was quantitative. After recrystallization from t-butyl alcohol, the yield was 97 per cent. Satisfactory halide analyses were obtained only after this recrystallization. Isopropyltrimethylammonium bromide.--To 125 ml. of acetone which had been 19

chilled in a 500 ml. ground glass stoppered Erlenmeyer flask in an ice

bath was added 69 g. (0.73 mole) of methyl bromide. Thirty-five grams

(0.42 mole) chilled dimethylisopropylamine was added, which immediately gave rise to a white cloudiness in the reaction mixture. The reaction

flask was swirled about in the bath to prevent overheating. After about ,

45 minutes the flask was removed from the bath and allowed to stand on the desk. The stopper blew out and the solvent evaporated, so that con-

siderable white solid substance was left in the flask. The flask was

chilled by a dry ice-acetone mixture and 200 ml. of dry ether added.

The flask was stored in the refrigerator for two days. The salt was

isolated by suction filtration and dried in the vacuum oven for 16 hours

at 600 . The yield of salt was 91 per cent. The ionic halogen analysis indicated that recrystallization was not necessary.

Isopi0.2z1tKimelammum iodide.--A solution of 49.0 g. (0.56 mole) of dimethylisopropylamire in 125 ml. of methyl ethyl ketone was chilled in a dry ice bath. To this solution was added 46 ml. (0.74 mole) of methyl iodide. After cloudiness had appeared in the reaction flask, it was removed from the bath and carefully watched. At the first overt sign of reaction, the flask was returned to the dry ice bath and shaken, but the reaction gained such force that all the solvent evaporated, with some spattering of salt. After addition of 150 ml. of dry ether, the salt was isolated by suction filtration, and dried in the vacuum oven for three hours at 40°. The yield of salt was 95 per cent. Analysis for ionic halogen indicated that recrystallization was not necessary.

Trie_t4y1met. 3__AL.,._a_ammwnii iodide.--To a solution of 139 ml. (1.0 mole) of 20

triethylamine in 500 ml. of methanol which had been chilled in a dry ice- acetone bath was added 64 ml. (1.03 moles) of methyl iodide. The stopper of the flask was wired loosely in place and the flask was placed in the refrigerator. Fifteen minutes later the solution was colorless and felt warm to the touch. Consequently it was returned to the dry ice bath overnight. The flask was then removed from the bath and allowed to remain at room temperature for six days. The reaction was complete at this time, as indicated by titration of a small aliquot of the reaction mixture with standard hydrochloric acid. Four hundred milliliters of dry ether was added, causing a momentary precipitation of salt. Seven- teen days after the addition of the ether, a mass of crystals was found at the bottom of the flask. Most of the mother liquor was decanted and inadvertently discarded. The crystals were filtered from the remaining mother liquor and washed with portions of dry ether. The ether washings, as they were added to the filtrate, led to precipitation of further material in the filtrate. The salt was dried in the vacuum oven. The yield was 47 per cent. Analysis for ionic halogen indicated that recrystallization was unnecessary. aietlm4EtAylatmuoniurabromide.--To a solution of 127 g. (1.34 moles) of methyl bromide in 350 ml. of acetone, contained in a 1000 ml. ground glass stopper' Erlenmeyer flask and chilled by means of a dry ice-acetone bath, was added 136 ml. (0.98 mole) of triethylamine. After an hour the flask was removed and allowed to approach room temperature. Suddenly the reaction became vigorous enough to cause the solution to boil. The flask was returned to the dry ice bath, and after three minutes of shaking 21

the boiling ceased. The reaction mixture was then allowed to warm to

room temperature. Two hundred milliliters of dry ether was added and

the flask stored in the refrigerator for a day. The salt was isolated by suction filtration and dried 16 hours in the vacuum oven at 60°. The yield was 93 per cent. Ionic halogen analysis indicated that there was

no need for recrystallization.

Triet lmet lammonium chloride.--To a solution of 79 g. (1.53 moles) of methyl chloride in 500 ml. of methanol, which had been chilled in a dry ice-acetone bath, was added 145 ml. (1.04 moles) of triethylamine. The mixture was then allowed to stand at room temperature for six days. The solvent was removed by distillation and the salt isolated by suction

filtration, with the aid of some dry ether. The salt was dried in the vacuum oven and the yield found to be 21 per cent. Since only a small amount of the salt was required, the reaction had not been allowed sufficient time to go to completion. The ionic halogen analysis indicated that the salt was quite pure and required no further crystallization. A later preparation gave 96 per cent yield of salt. EtALLEIR2thylaaaonium iodide. mho 336 ml. of 25 per cent trimethylamine in methanol, which had been chilled in a flask in a dry ice bath, was

added 75 ml. (0,88 mole) of ethyl iodide. After 21 hours in the dry ice bath, the flask was removed and allowed to warm to room temperature. After an hour voluminous crystalline material had appeared. Two days later 250 ml. of dry ether was added, causing precipitation of further salt. The salt was isolated by suction filtration and washed with dry

ether. The first crop of salt amounted to an 86 per cent yield. A 22

second crop of salt isolated from the combined filtrate and ether washings gave an additional yield of nine per cent, making the total yield

95 per cent. Ionic halogen snslyses indicated that recrystallization was not necessary.

Ethyltrimethylammonium bromide.--To 333 ml. of methanolic trimethylamine containing 1.0 mole of trimethylamine (333 ml. of 25 per cent trimethylamine in methanol), which had been chilled in a flask by means of a dry ice-acetone bath, was added 76.7 ml. (1.1 moles) of ethyl bromide. The stoppered flask was allowed to remain in the dry ice bath for two days.

When the flask was removed and allowed to warm to room temperature, the reaction mixture became hot. The flask was returned to the dry ice bath, and when the reaction had subsided, it was removed. The salt was isolated by means of suction filtration, with the aid of some dry ether for washing. The salt was dried in the vacuum oven at 85 ° . The yield of salt was 75 per cent. Halide analyses indicated that recrystallization was not necessary. Ttt,ulAmAigglalrpalsium bromide.--To a solution of 91 g. (0.96 mole) of methyl bromide in 500 mi. of methanol, contained in a flask in an ice bath, was added 350 ml. (1.05 moles) of 3.0 N trimethylamine in methanol. After two months at refrigerator temperature, the salt was isolated by suction filtration and washed with methanol. The salt was dried in the vacuum oven for two hours at 40°. The yield was 75 per cent. Analysis for halide indicated that recrystallization was not necessary. Chloromethy2I/latthylasmonlas chloride.--The salt prepared by Blanchard 21 was used.

2 lIbid., p. 88. 23

Chlorome talammnium. bromide.--The salt prepared by Blanchard was used. 22 2-Chlorq.ethffltrimetbylammonium chloride.--This salt was prepared accord- 23 ing to directions given by Gordon. To 201 g. (1.44 moles) of choline chloride which had been dried in a vacuum dessicator over calcium chloride was added 210 ml. (2.92 moles) of thionyl chloride. The choline chloride was contained in a three-necked flask fitted with a reflux condenser and a dropping funnel. The condenser was fitted with a Drierite drying tube to prevent the entrance of moisture. The thionyl chloride was added slowly from the dropping funnel at first, but when the reaction became sluggish, the final 50 ml. of thionyl chloride was added in one portion. After the reaction mixture had been refluxed for 30 minutes, thionyl chloride was removed from the reaction mixture by applying the vacuum of a water aspirator. Sixty milliliters of absolute ethanol was added and the vacuum of the water aspirator again applied. The odor of sulfur dioxide could still be detected emanating from the reaction mixture after this treatment. The salt was dissolved in a minimum ,t50 ml.) of hot absolute ethanol and a small amount of deodorizing carbon was added to the solution. The solution was boiled for three minutes and filtered hot. The solution was then concentrated until crystals of salt appeared, and a little absolute ethanol was added until all the salt was in solution. After two weeks storage in the refrigerator, the salt was isolated by suction filtration and

22 Ibid., p. 87. 23Gordon, a. cit., pp. 75-78. 24

immediately recrystallized from absolute ethanol. The yield of recrystal-

lized salt was 42 per cent. An additional yield of 40 per cent was ob-

tained from the concentrated filtrates from the two crystallizations.

The total yield was therefore 82 per cent. Analysis for ionic halogen

indicated that there was no need for further purification.

5-Chloroamyltrimet} la chloride.--To 88 ml. of 3.11 N trimethylamine in methanol in a 500 ml, ground glass stoppered flask was added

122 g. (0086 mole) of 19 5•dichloropentane. The stopper was wired on and the flask stored at room temperature for 13 days. The reaction was complete at that time, as determined by titration of a one milliliter aliquot with standard hydrochloric acid. The reaction mixture was concentrated by evaporation on the steam bath while a stream of dry nitrogen passed through the solution. After 75 minutes the mixture became cloudy, and after 105 minutes crystals appeared. The steam bath was removed, but the nitrogen stream was continued while the mixture cooled. The somewhat gummy crystals were isolated by suction filtration, with the aid of some dry ether. The salt was dried in the vacuum oven overnight. The yield of crude salt was 86 per cent. Ionic halogen analysis indicated that the crude salt contained 13 per cent by weight of bis-1,5-amylie. imethylammonium chloride and the remainder 5-chloro- amyltrimethylammenium chloride. The salt was extracted with tebutyl alcohol in two Soxhlet extraction thimbles. About two-thirds of the salt contained therein was extracted from one thimble, and about three- fourths from the other. Crystallization of the extracts took place overnight. The salt was isolated by suction filtration, and washed with 25

t-butyl alcohol and dry ether. Ionic halogen analysis of the purified

salt indicated that it contained no more than 0.8 per cent of the bis

salt by weight. The yield of purified material was 29 per cent. Columbia Organic Chemicals grade 1,5-dichloropentane was used in the preceding preparation. When Eastman Kodak white label grade of 1,5-dichloropentane was used, extensive treatment with dry ether was necessary before sufficiently crystalline material could be Obtained. Several previous preparations varying very little or not at all from the foregoing failed to give a product of sufficient purity, even after several extractions with t-butyl alcohol.

Chl_oronildiraetrlz■2t benzlanmionium bromide.--Attempts were made to prepare this salt from methylene chlorobromide and dimethylbenzylamine which react moderately readily. One hundred grams (0075 mole) of dimethylbenzylamine and 46 mi. (0.70 mole) of methylene chlorobromide were mixed in

600 ml, of acetone, and the reaction flask stored in the refrigerator. The reaction wa found to he complete after 50 days by titration of a one milliliter aliquot of the reaction mixture with standard hydrochloric acid. There were some crystals in the bottom of the flask, and the supernatant liquid was a brownish straw color. The mixture was heated for a few minutes oa a hot plate while a stream of nitrogen bubbled through it. When the mixture had cooled, 300 ml. of dry ether was added and the mixture returned to the refrigerator. After 17 days the ether and acetone were decanted, and fresh, dry ether was added. After five more days in the refrigerator, the mixture was chilled in a dry ice- acetone bath and the ether poured off. Two small portions of dry ether 26

were added and decanted immediately, then 500 ml, of dry ether was added and the mixture returned to the refrigerator. White solid material in the bottom of the flask was of about the same consistency as biscuit

dough. After four more days the ether was decanted from the mixture and

500 ml, of fresh, dry ether was added. Ninety-two days later the reaction flask was found in the refrigerator with the stopper blown out. Some

ether and the cake of salt remained. In the course of removing the salt the flask was broken and some of the salt lost. The very hygroscopic

salt was placed on a coarse fritted glass filter and washed twice with ether. The yield of crude salt was 84 per cent. The salt was dried in the vacuum oven for 48 hours. The temperature of the oven was 70° for

16 hours of this time and lower temperatures for the rest of the time. When removed from the vacuum oven the salt was found to have sintered together, and was a light tan in color. The gummy material, which had a lachrymatory odor, was kept in an open beaker in a desiccator cherged with phosporus pent oxide. From a test reaction of methyleas chlorobromide with dimethylbenzylamine i dioxane were obtained some crystals of salt of good appearance. These were placed in a drying pistol heated by refluxing acetone, and the vacuum of a vacuum pump was applied for two days. At the end of this time the material was no longer crystalline, but had sintered together anl become light brown. A white solid had sublimed on the cooler far end of the drying tube. In a cold trap protecting the vacuum pump were found some tetrahedral crystals which were possibly benzyl bromide On. p. bengyl bromide, -4.0 °). As the trap warmed to room 27 temperature these melted to a brownish-orange oil, which amounted to one milliliter. The oil was shaken with silica gel to remove vater; the suspected benzyl bromide was then treated according to the procedure of Shriner, Fuson and Curtin to prepare the anilide. 24 The nnknown oil was added. to 15 ml. of ether and 0.3 g. of magnesium turnings contained in a test tube, and a crystal of iodine added. A fine stream of bubbles came off the magnesium. The ether solution was filtered through a glass wool plug into another test tube containing 0.5 ml. of phenyl isocyanate in 10 ml. of dry ether. The mixture was shaken vigorously with 25 ml. of two per cent hydrochloric acid and separated by means of a separatory funnel. The separated ether layer was dried by magnesium sulfate and filtered, and the ether distilled. When the material in the pot had reached a small volume, it was taken up in hot methanol. The methanol solution was cooled, then chilled until needle-like crystals separated. These melted at 241° uncorr. The melting point of the anilide derived from benzyl bromide is 117 0 . 25 The melting point of carbanilide, a common impurity in phenyl isocyanate, is 2380 0 26 The white sublimate was quite hygroscopic. Each of four tests with slightly acidic (nitric acid) silver nitrate solution gave a white precipitate, indicating the presence of ionic halogen. The sublimate is possibly dimethylmethylene'' iminium chloride, CH2 N(CH3 ) 2C1. 27 Halide analyses on this compound

24R. L. Shriner, R. C. Fuson, and D. Y. Curtin, The §ystematic Identification of d Compounds , a Laborato Manual, Fourth Edition, New York, John Wiley and Sons, Inc., 195 , p. 2. 25Ibid., p. 309. 26Ibid., p. 287, 27T. D. Steward and W. E. Bradley, J. Am. Chem. Soc., 2L1, 4172 (1932); C. R. Hauser, ibid. 7.2, 5514 (1957T, 28

were impracticable because of its hygroscopicity and its volatility in vacua.

Preparation of Amines

121:2.Lutall2thylantint.--This amine was prepared from di-n-butylamine by an adaptation of the procedure given in Organic Syntheses for the methylation of phenylethylamine. 28 A two-liter boiling flask which contained

515 g. of 85 per cent formic acid was immersed in ice. Two moles (337 ml.) of di-n-butylamine was added slowly from a dropping funnel. After all the amine had been added, 225 ml. of 40 per cent formaldehyde was added. A reflux condenser was put in place, and heating of the flask begun by means of on electric heating mantle. Some formaldehyde was lost through the condenser at one point; consequently, an additional 75 ml. of formaldehyde was added through the condenser. The pot temperature was 65° at this point. Seventy-five minutes later, when the temperature had reached 800, the heat was turned down. The next day the heat was turned up so that the pot remeined at 90 to 95 ° until the following day. The flask was cooled, and 1000 ml. of 4 i hydrochloric acid was added. The material was evaporated down to a yellow oil in the course of ]J4 haurs by means of a steam bath and suction of a water aspirator. Six hurdred milliliters of water was added and then 500 ml, of water containing mina equivalents of sodium hydroxide was added. The layers were separated and the top (amine) layer was decanted from potassium hydroxide pellets. The crude yield was 93 per cent. The

28E. C. Horning, Organ Syntheses, New York, John Wiley and Sons, Inc., 1955, vol. III, p. 723. 29

amine was distilled through a one-foot glass helix packed column at b. p. (main fraction) of 161.2-162.2 ° at 749 mm. The yield of purified amine was 84 per cent.

Dimethyl-sec-butlaine.--This amine was prepared by methylating sec- butylamine with formaldehyde and formic acid. 28 From a dropping funnel,

43 g. (0.59 mole) of seco'butylamine was added slowly to 163 g. of 85 per cent formic acid (ca. three moles) contained in a liter boiling flask which was immersed in ice. After 135 ml. of 37 per cent formaldehyde had been added the solution was heated. A slow evolution of carbon dioxide began at 35° and a moderate evolution at 45 ° . The heat was turned off when the pot temperature reached 58° . When the temperature had reached 65° the mantle was removed, but the temperature continued to rise. When the temperature had reached 75 ° an ice bath was used to moderate the reaction until the pot temperature fell to 67° ; upon removal of the ice bath the temperature rose to 70 ° and the heating mantle was replaced. The reaction was self-sustaining for a time at 70° . The heat was then turned on so as to keep the pot temperature at 83-89° for 39 hours, after which there was no more apparent evolution of carbon dioxide. The flask contents were cooled to 30°, 300 ml. of 4 N hydrochloric acid was added, and the mixture was concentrated to a clear brown syrup in the course of 21 hours by heating on the steam bath and application of the vacuum from a water aspirator. To the ice-chilled syrup was added 150 ml. of chilled 18 N sodium hydroxide solution. The addition of the base was necessarily slow owing to the ebullition it initiated in the mixture. The mixture 30

was transferred to a reparatory funnel, and after the addition of some water to dissolve solid material, the layers were separated. The crude yellow amine was shaken with potassium hydroxide pellets and allowed to stand 48 hours, at which time the yellow color had lightened considerably.

The amine was decanted into a distilling flask and distilled through a foot-long vacuum jacketed column packed with glass helices. Some volatile material at first boiled out of the mixture but did not condense.

It was detected exuding from one of the open necks of the distilling head.

There was a forerun boiling at 82.3-92.8° . The fraction taken to be dtmetbyl-sec-butylamine boiled 92.8-93.00 at 739 mm. The purified yield was 64 per cent. The crude yield was 82 per cent, but the crude material is believed to have contained some vater.

Dimethzi:Lhatylamine.--This amine was prepared by metbylating t-butylamine with formaldehyde and formic acid. 28 To 470 g. of 85 per cent formic acid (807 moles) contained in a two liter boiling flask surrounded by ice was added very slowly 182 ml. (1.74 moles) of t-tutylamine. The ice bath was removed, 390 ml. of 37 per cent formaldehyde added, and the mixture heated. No evolution of carbon dioxide was apparent until the pot temperature had reached 60-65 °, whereupon the heating mantle was removed. After about one and one-half hours the pot temperature was less than 500 , and the evolution of carbon dioxide was slow, The heating mantle was replaced and the heating resumed until the pot temperature reached 8085° and the reaction became vigorous. The heating mantle was removed. Condensing liquid was observed near the top of the condenser and evidently some of the reaction mixture escaped by entrainment 31

in the evolved gas. The heating mantle was replaced and the heat left on at a low voltage setting overnight. The next morning the pot tempera-

ture was 55-60° , with a steady but slow evolution of carbon dioxide. The heat was advanced so as to keep the pot at 85° for 24 hours, after which time there was no more apparent evolution of carbon dioxide.

After the reaction mixture had been cooled to 45°, 868 ml. of 4 N hydrochloric acid was added. The mixture vas concentrated to a mass

of moist white crystals by heating with the steam bath and applying the

suction of the water aspirator for a total of 18 hours. The residue was taken up in 300 ml. of water and chilled in an ice bath. Addition

of 435 ml. of 18 N sodium hydroxide solution led to separation into two layers. The amine layer, after separation, was dried for five minutes over potassium hydroxide pellets and weighed. The crude yield was 97 per cent. The amine was dried over potassium hydroxide overnight and decanted onto clean, dry potassium hydroxide pellets. After ten minutes the aelizee was decanted into a clean, dry boiling flask and distilled through a 15 inch vacuum jacketed column which was packed with glass helices. Four milliliters of forerun boiling at 76.1-88.3 ° ° at 740 mm.„ as was taken off. The main fraction boiled at 88.389.2 compared to 89-90 ° recorded in the literature for dimethyl-t-butylamine. 29 The yield of purified amine was 85 per cent.

Di.ztekblislc2kr2zrlamine.--To 200 g. of 98 per cent formic acid and 320 g. of 85 per cent formic acid contained in a flask chilled by an ice bath

29N. Bortnick, L. S. Luskin, M. D. Hurwitz, W. E. Craig, L. J. Exner and J. Mirza, J. Am. Chem. Soc., /E!, 4040 (1956). 32

was added 123 g. (2.08 moles) of isopropylamine very slowly from a dropping funnel. Forty per cent formaldehyde (46o mi.) was then added to the chilled mixture. The reaction flask was placed under a reflux condenser and heated to 68 °, from which temperature the evolution of carbon dioxide continued without external heating and the temperature of the pot went spontaneously to 84 ° . After the evolution had subsided, the pot temperature was adjusted to 90 ° and sustained there for

6o hours. The contents of the flask were cooled and transferred to a larger flask with 1000 ml. of 4 N hydrochloric acid. Evaporation to white crystals was attained in six hours by means of the steam bath and the water aspirator. The flask was cooled, and 600 ml. of water added. One thousand milliliters of 4 N sodium hydroxide solution was then added through a reflux condenser. There was, however, much vola- tilization of amine. The layers were separated and the amine layer was found to amount to a 76 per cent yield of crude amine. The amine was

shaken with potassium hydroxide pellets, decanted onto fresh potassium hydroxide pellets, and allowed to stand three days. The amine was then decanted onto fresh potassium hydroxide and allowed to stand one hour. It was filtered through a glass wool plug into a distilling flask and distilled through a foot long column packed with glass helices.

There was considerable forerun, boiling over the range 25.063.8 ° . The main fraction, obtained in 41 per cent yield, boiled at 63.864.2° at

740 mm.

Purity of Compounds

Halogen anal e2, "-The principle criterion of purity of the quaternary 33 ammonium salts was the agreement of found with calculated values for ionic halogen. Argentimetric titration methods were used for the deter- minetion of ionic halogen. Samples of the salt to be analyzed were weighed out so as to require about 40 ml. of 0.1 N silver nitrate solution. The samples were dried in the vacuum oven overnight or longer at 70-85° . The samples were weighed after drying and the weight of the samples determined by difference. Each sample was transferred to an

Erlenmeyer flask together with at least three water washings of the weighing bottle. Two titration methods were used: absorption indica- tor3° and Volhard. 31 The Volhard titration was used when the absorption indicator titration did not give a sharp end point. Better results were obtained when the titrations were carried out in the absence of fluorescent light. 32 In the absorption indicator titration seven drops of 0.5 per cent dichlorofluorescein in 70 per cent aqueous ethanol were used as indicator. It was found best to carry out the titrations as rapidly as possible. Results of halogen analyses are given in Table 1,

Melt ing pstsits.--,The melting points of some of the quaternary ammonium halides, and their picrates (where they formed) were determined on samples dried overnight or longer in the vacuum oven and stored in a phosphorus pentoxide dessicator until the melting points were run. An electrically heated block was used. A melting point was first taken

301. M. Kolthoff and. E. B. Sandell, Textbook of Quantitative Inorganic hmILELE, Third Edition, New York, The MacMillan Company, 1952, P. 5 3. 31Ibid., p, 545.

32J, A. Bishop, J. Chem, Educ., 31 372 (1956). 34

Table 1. Results of Ionic Halogen. Analyses

% Halide Compound Found Calc. n-BuMeNI 28.11b / c 28.51 3 28.64b,c

28.51a 28.55a 28.58a n-Bu3MaNI 38.10 38.78 n•13u2Ma2NBr 33.41 33.55 34.25 12-Bu2me2NI 41.99b 44.50 42.64b

38.77] n-BuMe3NC1 23.41a' c 23.40 23.38a,c 23.43a,c 23.38a,c 23.29e,a 23.3082a 23.281:Y a 23.24 ,a 23.35'Y a n-BuMeNBr 40.68t 40.74 3 41.99 n-BuMegI 52.01b 52.19 51.46b s-BUMelNI 51.72a 52.19 51.73a 51.67a 51.55a 35

Table 1. (continued)

% Halide Compound Found Calc. t-BUMe3NI 52.51a 52.19 a 52.14 n-PrOBr 29.96,b, 30.01 30.19u n"Pr3MeNI 41-26t ,i; 44.50 43. 07 Yj 42. 81t t 42.44 9 1 n-PrMegi 54.7213 55.40 , 54.84 55.34134 55.4012'4 i-PrMe NI 43.79,,b 43.88 3 43.35° i-PrMe.-NI 55.19b 55.40 ® J 55.12b

Et4NBr 37.84b 38.03 37.90,b 37.96- Et, Mean 23.38a 23.38 23.32a 23.42a 40.74 Et 3MeNBr 40.45„ 40.57° Et3MeNI 51.95a 52.19 52.058 p EtMe3NI 59.39 59.01 58.75b EtM-ABr 47.43, 4758 47.31'

Table 1. (continued)

% Halide Compound Found Calc.

Melpr 51.52b 51.86 51.44b

Me 0C1 32.19a/ c 32.35 32.41a/ c

C1CH2CH2N(CH3)3C1 22.28a9e 22.43 22.35aY e

22.31a / f

C 1CH2CH2CH2CE2CH2N(CH3)3C1 17.81a/ e 17.73 17.83a,e

18.40f 18.09f

19.4f ; u

18.39g 18.73g

/7.78.hk 17.81"

Thee values were obtained by an absorption indicator titration.

bThese values were determined by Volhard titration.

This analysis was made on a salt preparation made by Blanchard. 2°

These values were determined on first batch of salt prepared.

fTbese values were determined on second batch of salt prepared.

slhese values were determined on third batch of salt prepared.

These values were determined on fourth batch of salt prepared. 37

Table 1. (continued)

iEnd points were uncertain on these determinations. iThese values were obtained on recrystallized salt. uAnalyses were done on salt recovered from filtrates after extraction with t-butyl alcohol that is on a second crop of crystals. 38

with rapid heating after which the block was cooled ten to twenty degrees and a second. sample in a melting point tube was introduced. The block was then heated at two degrees per minute to the melting point.

Many of the salts did not melt, but decomposed, usually with charring.

Melting points obtained are given in Table 2.

Derivatives.--The picrates of some of the salts were prepared as described by Blanchard. 33 To about 25 ml. of a saturated ethanolic picric acid solution was added a 10 ml, ethanolic solution of the salt. If picrates did. not form in the cold, the mixtures were warmed on the steam bath for a few minutes. The picrates, where they formed and crystallized., were recrystallized from eth n01, washed with dry ether, and dried in melting point tubes in the vacuum oven. No derivatives of amines were prepared. Melting points of picrates are given in Table 2.

Neutralization emivalent so--In the case of dimethyl-t-butylainine, an attempt was made to obtain a neutralization equivalent. Values of 106 and 98 respectively were obtained (calculated value, 101). The method was to weigh a flask containing excess standard hydrochloric acid., discharge an amine sample into the flask, reweigh, and back titrate with standard sodium hydroxide solution. Since the amines were all intermediates in the preparation of quaternary ammonium salts, it was decided to allow the halide analysis of the salts to serve as the final criterion of purity.

Custallization..--Many of the salts prepared came down from the reaction

33Blanchard, 2.. cit., p. 34. 39

Table 2. Melting Points of Quaternary Ammonium Halides and Picrates

o Compound Melting Point °C Picrate m.p. C Obs. Lit. Obs, Lit. n-Bu2Me2NBr 166. 0-6. 2

E-33112Me2Ni 153.4-4.0 149-504 n-BUMe RBr 208.1-9.7 197-835 3 36 n-BUMe3NI 231.7-3.8 229-30 s-BUMe3NI 266.4-6.6 t-BuMe3NI 260.1-0.5a 258a, 37 38 n-PrMe3NI 192.0-3.5 192.0-2.5 i-PrMe3NBr 317•1a i-PrMe3NI 316.0-6.8a 30539 o Et3MeNBr 307.4a 273.6 276.5-7.4 41 Et MeNI 3084 -9.5 a 288.7-9.1 290 3 EtMe3NBr 322-5.6a 305.0

EtMe3NI 337.6-8.4a 320-2a' 42 306.0

aThe salt melts with decomposition.

3 14. D. Emmons, E. S. McCallum, and J. P. Freeman, J. Q. Chem., 120 1472 (1954).

35C. D. Bard and L. R. Drake, J. Am. Chem. Soc., 61 1943-5 (1939).

361. Marzak, J. P. Guermont and R. Epsztein, Mem. services chim. etas, 26, 301 (1951). 37Bortnick et al 2R. cit., p. 4041.

38P, A. S. Smith and S. Frank, J. Am. Chem. Soc., 74, 512 (1952). 40

Table 2. (continued)

39A. Ries, Z. Kriot., 22, 487 (1915-1920). 4°R. 0. Clinton and S. C. Laskowski, J. Am. Chem. Soc., 2226 (1952). 41S. Honig and W. Baron, Chem. Ber., 22, 395 (1957). 42S. Wawzanek and D. Meyer, J. Am. Chem. Soc., 16, 2918-20 (1954). mixtures as oils, necessitating repeated treatments with dry ether to induce crystallization. In general, the more hygroscopic salts tended to form oils. For a salt of a given cation, the chloride is more hygroscopic thrn the bromide, which in turn is more hygroscopic than the iodide. Many of the iodides could be handled without special pre- cautions to exclude moisture. It was usual in filtration of the more hygroscopic salts to employ a rubber dam over the funnel and a drying tube in the line from the water pump to the filter flask. Dry ether, used in washing the salts, helped to keep the salts crystalline on the filter. Many of the salts gave halogen analyses indicating that no recrystallization was required. The solvent used for recrystallizing the most hygroscopic salts was t--butyl alcohol. Isopropyl alcohol was used for recrystallization of salts of intermediate hygroscopicity, and for the least hygroscopic salts methanol and ethanol were adequate recrystallizing solvents. Specific solvents used in the preparation and recrystallization of specific salts are mentioned in the sections dealing with the preparation of the salts.

Nev prtaIaLiam.•-Examination of the literature revealed no prior preparation of the salts 5-chloroamyltrimethylammonium chloride, di-n- butyldimethylammonium bromide, or isopropyltrimethylammonium bromide.

The preparations of di-n-butylmethylamine, dimethyl-secebutylamine, dimethylisopropylamine, and dimethyl-t-butylamine are believed to represent the first tacy heses of these amines by formic acid-formaldehyde methylation.28 42

CHAPTER IV

ANALYSIS OF PRODUCTS

Aaicaln hnL3.--The principle problem of analysis in this work was the estimation of the relative amounts of methane and a higher alkane in a gaseous hydrocarbon mixture diluted with about four times its volume of nitrogen. This was accomplished by means of an infrared analytical technique. A Perkin-Elmer Model 21 spectrophotometer equipped with a removable ten-centimeter open-path gas cell with rock salt windows was used to measure absorption of infrared light by the samples.

Calibration curves were prepared from optical density measurements made on known samples of methane, ethane, propane, butane, isobutane, ethylene, butene-1, and isobutene. Preparation of the samples and measurement of the optical density were carried out as follows: The 43 gas handling apparatus designed by Blanchard was used. This apparatus was constructed of a 5/8 in o. d. horizontal glass tube 27 in. in length which had 18/7 socket joints at each end and was equipped with four stopcocks joined to it at right angles. A 3/16 in. o. d. glass tube of one meter length attached at right angles to the horizontal tube dipped into a reservoir of mercury. A mercury manometer was joined to one end of the horizontal tube by one of the 18/7 ball and socket joints. The infrared gas cell could be attached through the remaining 18/7 ball and socket joint. A vacuum pump was connected to one of the

43Blanchard, op. cit., p. 39. 43 stopcocks of the gas handling apparatus by means of heavy wall rubber pressure tubing. A nitrogen tank was connected to a second stopcock, and a tank of the gas to be calibrated to a third. The cell stopcock and the stopcock leading to the valve on the alkane cylinder were opened.

The system vas successively evacuated and filled to atmospheric pressure two or three times with nitrogen, and then two or three times with the gas to be calibrated. All stopcocks except that on the gas cell were closed. The stopcock to the vacuum pump was opened slightly and the system evacuated to a pressure of between 100 and 300 mm. as read on the mercury manometer. The cell stopcock was closed, and the system outside the cell successively evacuated and filled with nitrogen two or three times. The system outside the cell was now at or near atmospheric pressure. The cell stopcock was opened slightly to admit nitrogen to the cell; the nitrogen tank valve was opened slightly to admit more nitrogen until the entire system, including the cell, was near atmospheric pressure, after which the cell stopcock was closed. The tank valve was closed and this pressure (near atmospheric) was recorded. The temperature was recorded, the system outside the cell evacuated, and all stopcocks closed. The cell stopcock was opened slightly and the pressure allowed to equilibrate in the system. The system was then evacuated to a pressure which gave the desired partial pressure of the gas to be calibrated.

The pressure of the system was recorded and the cell stopcock closed. Nitrogen was then admitted to the cell by the procedure described above to bring the total pressure near that of the atmosphere, and this pressure 44 recorded. By repeated applications of this method, successively smaller

44 bid., p. 44. 44

partial pressures of hydrocarbon in a total pressure of one atmosphere could be obtained from one initial sample. At least one independent sample was, however, taken in a similar way so as to detect any error which might have occurred in the manipulations. A numerical example of the ga dilution technique is as follows:

Sample C H taken: 3 8

240.9 mm. C 3H8 at 30®

Brought with N2 to pressure:

741.7 mm.

Sample expanded to:

165.8 mm.

Pressure C H in succeeding sample: 3 8

165.8 x 240.9/741.7 = 53.9 mm.

Brought with N to pressure: 2

741.6 mm.

The method used to determine the optical density at the desired wavelengths was a "cell in-cell out" method. The spectrophotometer was zeroed and set at 100 per cent transmission with the cell out at 7069 microns. The purpose of always making these settings at this wavelength was to avoid having to reset the spectrophotometer at other wavelengths 45 for gases other than methane during an actual analysis. With both the sample and the reference beams closed, the pen was given a slight drift upscale (toward 100 per cent transmission). Direct reading optical density paper was used. For samples of methane, the cell was placed in the path of the sample beam, and the sample slowly scanned from about 0.01 microns before to the same value after the maximum (vicinity of 7.69 microns). Fixed wavelengths were chosen for calibration of each of the higher alkanes. These were set by running the wavelength counter in the reverse direction (from long to shorter wavelength) and stopping it at the desired wavelength. While the cell containing the sample was in the sample beam, the shutter of the reference beam was partially closed, so as to cause the pen to come to rest upscale. The pen was then set on the paper and the shutter opened. The optical density reading was taken to correspond to the point where the pen came to rest. At least four of these measurements were made on each sample. The optical density of the cell was also determined at the requisite 'wavelengths. Gaseous olefins were calibrated by rapid scanning (at the same speed as ordinarily used for qualitative scan) through the wavelengths at which they were to be calibrated, so that semi-quantitative estimates of these gases could be made directly from the scan. Methane was calibrated near 7069 microns by a scanning method, and at fixed wavelengths of 3.455 and 3.445 microns. Ethane, propane, butane, and isobutane were all s librated at fixed wavelengths. Ethane was calibrated at 3.445 and

6.820 microns; propane at 3.445, 3.450, 3.455, and 6.825 microns; butane at 3.455 and 60840 microns; isobutane at 3.455 and 6.788 microns; ethylene at 10.54 and 10.97 microns; butene-1 at 6.12, 10.54, and 10.97 microns; isobutene at 11025 microns. The appearance of three decimal 46

places in the wavelength figure indicates that the calibration was done at fixed wavelength; otherwise, a scanning method. was used.

The analysis of gas from a reaction was accomplished as follows: A gas sample was brought into the gas burette of an Orsat apparatus (fitted with ground glass connections) and, if necessary, bubbled through dilute 0.5 to 1.5 N hydrochloric acid in saturated brine to remove ammonia. The volume was then read, the sample was passed through 22 per cent mercuric sulfate in 22 per cent sulfuric acid in order to remove unsaturates!4-5 and the volume was again read. The sample was then passed into a gas pipette containing concentrated sulfuric acid in order to remove water vapor. This pipette was connected by means of pressure tubing to a stopcock of the gas handling apparatus. The gas handling system was evacuated up to the pipette stopcock, and the stopcock to the vacuum pump closed. The pipette stopcock was then opened slightly so as to admit the sample to the cell. Successive samples could be introduced in this manner. After reading the pressure of the sample taken by means of the mercury manometer, the total pressure in the cell was brought to one atmosphere with nitrogen as described above. The temperature was recorded, and the cell taken to the spectrophotometer and scanned fro ► 2 to 14 microns to confirm the removal of all unsaturates. Optical density measurements were then taken at 3.455 or 3.445 microns, aepending upon the higher alkane to be determined. If the higher alkane was present at pressures in excess of five to ten millimeters, optical density measurements were also taken at some fixed wavelength, depending on the alkane, between 6.82 and 6.85 microns. These wavelengths had a

45A. W. Francis and S. J. Lukasievica, Ind. ERE. Chem., Anal. Ed,, 6, 703 (l945). 47 weaker absorption for the alkanes than did the 30445 and 3.455 micron wavelengths. Consequently, the calculated results of higher alkane yield used in determining methane to higher alkane ratios were based on determinations at the latter wave lengths. In the usual case, the sample was then diluted so as to get a readable optical density at the absorption maximum of methane at 7.69 microns. The corresponding partial pressure of methane was then determined from the calibration curve, and the partial pressure of methane in the undiluted sample calculated by means of the perfect gas law from the temperature and pressure data A methane sample was then prepared to correspond as closely as possible to this partial pressure. The optical density of the cell containing the methane sample was then measured at the wavelength(s) where the optical density measurements for the higher alkane had been made. This procedure was preferred to using a calibration curve for methane for the corrections, since the optical density of the cell filled only with nitrogen did not then have to be taken, either in the analysis or in making the methane calibration curve. The net result was that one less measurement on the cell had to be taken, and consequently the error estimated due to the noise level of the machine was less. The methane correction calibration curve in the vicinity of 30445 to 3.455 microns also appeared not to be reproducible with the desired accuracy on different days (see next section). An error, based on a geometric combination of the average deviation from the mean of the several optical density measurements and the calibration error, was assigned to all methane to higher alkane ratios determined by the method here described in detail. This error was determined as 18 follows: The average deviation from the mean of the pressures corresponding to the several optical density measurements was squared; an error assigned to the calibration curve on the basis of typical variation of the measured partial pressure of a synthetic sample from that measured by the calibration curve was also squared. The sum was divided by two and the square root taken to give the combined error on, for example, the methane yield. The error on the alkane yield was similarly estimated. The error in the methane to alkane ratio was also estimated by combining the error in the methane and in the alkane determination by the root mean square method. Oases containing unsaturates could be conveniently analyzed only in the dioxane runs. This sample was usually taken by passing about 1500 ml. of the gas from the gas burette of the Orsat apparatus through a foot-long drying tube filled with Drierite, thence into the gas cell.

This sample was scanned from 2 to 14 microns on the same optical density paper which had been used to scan the hydrocarbon sample, minus unsaturates, from the same reaction. By using this previous scan as a reference line, fair estimates of the yields of ethene, butene-1 1 and isobutene could be obtained. In other cases, this scan was used merely for qualitative identification of the unsaturates.

A typical analysis, showing numerical data, follows. This data was taken from the analysis of the gases from the reaction of sec- butyltrimethylammonium iodide with sodium in dioxane.

Moles salt taken:

0.0946 149

b Volume gas in collection bottle:

9600 ml. at 36® and 741.3 mm. (atmospheric pressure)

Correction for negative head of brine:

-17.7 mm.

Actiml pressure in gas collection bottle:

741.3 - 17.7 = 723.6 mm.

Volume gas corrected to S. T. P.:

(9600 x 273 x 723.6)/(309 x 760) = 8o80 ml.

b Moles gas in collection bottle:

8080/22 2 414 = 0.360 (wet)

Gases qualitatively identified by infrared scanning:

ethylene, ° acetylene, c butene-1, butene-2, methane, and butane

Pressure at which sample containing unsaturates was taken:

741.3 mm.

Optical density of sample at 6.]2 microns:

0.202

b Gas was collected over brine. At 36 ° , 4.5 per cent of gas volume over saturated brine is water vapor. ° Identified by a single typical strong band in the infrared at 10.54 microns for ethylene and 13.67 microns for acetylene. 50

Optical density of sample, unsaturates removed, at 6.12 microns:

0.101

Corresponding pressure (from calibration curve) of butene-1:

16.7 mm. at 31.

Corresponding pressure of butene-1 at 36 ° :

17.0 mm.

Pressure,9f unsaturate containing sample, had water vapor not been removed: 4°

741.3/0.955

Yield butene-1:

(17.0 x 0.955 x 0.360 x 100)/(741.3 x 0.0946) 22.8.4%

Optical density of unsaturate containing sample at 10.54 microns:

0.371

Optical density of sample, unsaturates removed, at 10.54 microns:

0.140

Optical density of 16.7 mm. butene-1 at 10.54 microns (from calibration curve):

00068

Optical density due to ethylene:

4 Blanchard, 2E. cit., p. 1010 51

0.371 - (0.140 + 0.068) = 0.163/4e

Corresponding pressure of ethylene from calibration curve, 31 ® :

3.0 mm.

Yield ethylene:

(309 x 3.0 x 0.955 x 0.360 x 100)/(304 x 741.3 x 0.0946) = 1.50

Mole fraction unsaturates in gas collection bottle (determined by chemical absorption):

0.0392 0.002

Total yield unsaturates:

(0.0392 x 0.360 x 100 x 0.955f )/0.0946 = 14.2 ± 0.8%

Yield butene®2 and acetylene (principally butene-2), by difference:

14.2 - (1.5 4- 8.4) = 4.3 0.8%

Pressure at which gas sample (=saturates removed) was taken:

742.1 mm. at 36° C.

Pressure of sample had unsaturates and water vapor not been removed:

742.1/0.916g = 811 mm.

dThe error in determining this value was not readily estimable. eAbsorption of butene-2 and acetylene at this wavelength was unknown and was therefore neglected. (Water vapor correction = 1.000 - 0.045 = 0.955 gCorrection for water vapor and unsaturates: 1.000 - (00045 + 0.039) = 0.916 52

Optical density at 6.840 microns:

0.293 ± 0.001

Optical density of cell containing 126 mm. CHh (as determined below) and nitrogen to atmospheric pressure at 60840 micons:

0.101 ± 0.001

Optical density due to butane:

0.192 * 0.002

Corresponding pressure butane at 23°C:

20.3 t 0.7 mm.

Pressure butane at 36 °C:

21.2 t 0.7 mm.

Sample expanded to pressure:

157.0 mm.

Sample brought with nitrogen to total pressure:

741.3 mm.

Optical density of expanded sample at 30455 microns:

0.465 ± 0.002

Optical density of 27 mm. CH and nitrogen to atmospheric pressure at 3.455 microns, including optical density of cell: 53

0.170 ± 0.001

Optical density due to butane:

0.465 ® 0.170 = 0.295 ± 0.003

Corresponding pressure butane, 23 ° C:

4.18 4° 0.092 mm.

Pressure butane at 36° C:

4.36 0.096 mm.

Pressure butane in original sample:

(4.36 x 742.1)/157.0 = 20.6 t 0.45 mm.

Per cent difference in butane determinations at 6.840 and at 3455 microns:

(21.2 - 20.6) x 100/21.2 = 2.8%

h Yield butane, based on 3.455 micron estimation of partial pressure:

(20.6 x 0.360 x 100)/(811 x 0.0946) = 9.52 t 0.22%

Optical density of expanded gas sample at the maximum nearest to 7.69 microns:

0.542 0.001

Optical density of nitrogen filled gas cell near 7.69 microns:

hThe 3.455 micron value was taken due to its higher optical density, and probable lower per cent error in its determination. 54

0.101 ± 00001

Optical density of methane:

0.542 ± 0.001 - 0.101 00001 = 0.441 ± 0.002

Corresponding pressure of methane (from calibration curve):

2607 0.6 mm. at 23° C

Pressure methane in unexpended sample

(26.7 x 742.1)/157.0 = 126.2 t 2.8 mm. at 23 ° C

Pressure methane corrected to 36° 0

(309 x 12602)/296 = 131.9 ± 2.9 mm.

Yield methane:

(131.9 x 00360 x 100)/(811 x 0.0946) = 62.0 t 1.4% patio of methane to butane

(131.9 1.° 2.9)/(20.6 ± 0.45) = 6.4o ± 0.20

Most of the reactions studied produce amines as well as hydrocarbons. The reaction gas was bubbled through two 500 ml. gas scrubbers with extra coarse fritted bubblers before passing it to the gas collection bottle. These scrubbers contained about 500 ml. total of dilute (0.3 to 0.5 N) hydrochloric acid containing a known number of equivalents of EC1. After a reaction in dioxane the yield of volatile amine 55

(assumed to be principally trimethylamine) could be determined by making the contents of the scrubbers up to one liter and titrating aliquots with standard base to a methyl red end point. If the total yield of amine was desired, the dioxane distillate (see Chapter V) was combined with the bubbler contents before making up to one liter. The total yield of amine could not be obtained in this manner when non-volatile amines, for example tri-n-butylamine, were produced.

In the case of the reaction of sec-butyltrimethyIammonium iodide with sodium in dioxane, the hydrocarbon analysis of which is outlined above, 0.1940 equivalents of HCl was taken for the scrubbers. After the reaction, the liter of solution made from the contents of the scrubbers was found to have a normality of 0.1686. Thus 0.1940 - 0.1686 = 0.0254 equivalents of HC] had combined with volatile amine, and the yield of volatile amine was (0.0254/0.0946) x 100 = 26.8 per cent. No yield of amines was determined for the reactions carried out in liquid ammonia.

Validity is indicated in the previous section, the present analyses for saturated hydrocarbons depend heavily on the accuracy of calibrations for infrared absorption. The purpose of this section is to show the reliability of these calibrations. All of the calibration curves (partial pressure of hydrocarbon as ordinate versus optical density at a given wavelength as abscissa) except that for methane were linear or very nearly so; they did not depart fram linearity except at higher values of optical density. The nature of the calibration plots is summarized in Table 3, where are given the values for partial pressure and optical density up to which the plots were linear. Figures 1 and 2 56 illustrate graphically those calibration plots of hydrocarbons other than methane which were non-linear throughout.

In most cases it was found possible to use linear portions of the higher alkane calibration curves in the analyses. The results of test determinations on synthetic alkane-methane mixtures are summarized in

Table 4. These results show that the method was, in general, satisfactory. However, the curvature of the methane calibration curve (7.69 microns) used in each analysis suggests the possibility that the presence of an alkane other than methane might cause changes in the optical density; that is, if higher partial pressures of methane cause a shift in the extinction coefficient of methane, the presence of other hydrocarbons might be expected to give rise to a similar effect. Blanchard states that partial pressures of butane as high as 37 mm. have such an effect and implies that a partial pressure of 11 mm. butane gives no detectable effect .47

The calibration curve used for methane during the major portion of this work was checked twice within a ten month period; the check values came within one per cent of the original values. After a new

Nernst glower had been installed in the infrared spectrophotometer, it was found necessary to make a new methane calibration. This calibration was about five per cent different from the older calibration at the worst and ten check calibrations, including one made with a different sample of methane, gave values checking within one per cent of the new calibration.

.7111■1.1.032-C, 47 Blanchard, 22. cit., p. 45. 60

z 50 O co

U O ce 40 >- I 0

E 30

a_re 20

a_ 10

0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 OPTICAL DENSITY • ISOBUTANE, 6.79 MICRONS, 31 ° A PROPANE, 6.825 MICRONS, 30 ° o ETHANE, 6.820 MICRONS, 28 °

Figure 1. Partial Pressure of Hydrocarbons vs. Optical Density Near 6.8 Microns. 40

w z IL121 30 _J < U- 0 ..--. E E ki j 20 0 in in w ce a. _1 a i- ce 1 0 a a.

0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 OPTICAL DENSITY

o BUTENE-1, 6.12 MICRONS, 31 ° • ETHENE, 10.54 MICRONS, 29 ° A ISOBUTENE, 11.25 microns, 28° (INCLUDES CELL 0.D.)

Figure 2. Partial Pressure Alkene vs. Optical Density. 59

Table 3. Linearity of Partial Pressure vs. Optical

Density Plots of Various Hydrocarbons

Hydrocarbon Wave Nature Plot Linear to Calibrated Length, of Plot microns Partial Optical Pressure mm. Density

Methane 7.69 Concave upward

Ethane 3.445 Linear 12.0 0,290 Ethane 6,820 Slightly curved

Propane 30455 Linear 7.0 0.410

Propane 3 0 445 Linear 5.0 0.267

Prop ne 3.450 Linear 5.0 0.289

Propane 6,825 Slightly curved

Butane 3.455 Linear 5020 0.365

Butane 6.84 Linear 79 0.800 Isobutane 6,79 Slightly curved

Isobutane 8045 Linear 110 0.407

Ethylene 10.97 Linear 15 00097

Ethylene 10.54 Curved

Butene-1 10.54 Linear 35

Butene-1 10.97 Linear 35 00:17:6 Butene-1 6.12 Slightly curved --- Isobutene 11,25 Curved 6o

Table 1.. Analyses of Synthetic Methane-Alkane Mixtures

Alkane Partial Pressure Partial Pressure Partial Per Cent Taken Alkane, mm. Methane, mm. Pressure Error Alkane Founda

Ethane 3.08 + 0.02 188.5 3.17 ± 0.04 3 Butane 3.68 144.7 3.74 2 Propane 4.31 119.6 4.30 + 0.02 0.2

Ethane 2.39 174.0 2.48 + o, 08 3.6 Butane 2034 183.1 2.36 1

Partial Pressure Partial Pressure Partial Pressure Per Cent Methane, mm. Isobutane, mm, Methane Foundb Error 2,61 100.5 2.5 + 0.1 4

o.5o 145 006 + 0.1 20

.Note that larger samples of alkane would give a lower per cent error.

bSweep method was used, but did not go below 7.685 microns. 61

It was found that concentrations of butane, propane, or ethane encountered in the analyses for this work do not affect the light absorption of methane at 7.69 microns, except for small contributions to the optical density. These contributions were corrected for by reference to a calibration curve for the higher hydrocarbon at 7.69 microns. On Figure 3 are shown the methane calibration curve at 7.69 microns and corresponding calibrations of methane containing the indicated proportions of higher hydrocarbon; these samples correspond to the maximum concentrations of alkane encountered in this work. The dotted line indicates the methane calibration used before the Nernst glower was changed.

It was not found to be convenient to use calibration curves for correcting for the optical density of methane at 3.445 and 3.455 microns.

Plots of partial pressure (corrected to 25 ® ) of methane vs. optical density at these wavelengths show considerable scatter; these data were collected on widely separated days, and correspond to the individual methane samples used in correcting the 3.445 or 3.455 micron optical density in the usual method of analysis employed in this work. The deviation from the best carve through these points was estimated at

*0.009 optical density units. Calibrations were also made at these wavelengths in the usual way. Two sets of calibration data gave one plot, and a third set gave another plot. These plots lay about 0.015 optical density units apart. The first two sets of data were taken on the same day, and the third set on another day. These calibrations, therefore, seem to be non-reproducible from day to day; they may, however, be reproduced on the same day. 62

The gain and resolution settings on the spectrophotometer were

found to be important in making optical density readings for methane at

7.69 microns. Thus, a partial pressure of 37.3 mm. of methane gave an

optical density of 0.561 ± 0.002 when the gain setting was 5 and the

resolution setting 965. With the other settings held constant, the same sample gave an optical density of 0.581 * 0.002 when the gain setting

was 6. The gain was set back to 5 and the resolution set at 927; the

optical density of the sample was then 0.650 ± 0.022. Changing the

light intensity from 0.34 to 0.40 amperes gave no noticeable effect. When all settings were returned to their usual values, the optical

density was 0.560 ± 0.003, in agreement with the original reading. As

care was taken in the analyses to ensure that the same settings were used on the spectrophotometer for all the samples, there should be little error from this source.

The data given in Table 4 indicate that the method of analysis was accurate within the limits given; the only further source of error remaining, then is the methane calibrations. The work done to show the reliability of these methane calibrations has been discussed above.

Perhaps there is a shadow of a doubt concerning the calibrations made at

7.69 microns, since the set of three calibrations made before installation of the new Nernst glower disagreed with the set of eleven calibra-

tions made after this installation. This disagreement was at a maximum

five per cent, with a possible consequential five per cent error in the methane to alkane ratios determined in actual analyses. Such an

error, if it exists, although undesirable, still leaves the data mean-

ingful with respect to the relative tendencies of alkyl groups to cleave from quaternary nitrogen. The evidence, however, favors the 40

0 CV

z 30

I-- w

E „ E 20

Ci_ -I 10 71 -

0 0 0.1 0.2 0.3 0.4 0.5 0.6 OPTICAL DENSITY o CH4, NEW NERNST • CH4/C3H8=10.0 A CH4, OLD NERNST CH4/C2H6 - 9.65 O CH4/C4H 1 0 = 6.92

Figure 3. Partial Pressure (mm.) of Methane at 25° vs. Optical Density at 7.69 Microns and Effect of Added Hydrocarbons on Methane Optical Density. 64

assertion that each set of methane calibrations was valid during the time it was used.

An ethane calibration at 3.445 microns was similarly found to have changed about four per cent. A piau ible explanation for the changes in the methane and ethane calibration curves might be that the gain control knob settings were changed when the Nernst glower was changed, since the panel holding this knob must be removed to gain access to the glower. 65

CHAPTER V

DESCRIPTION OF APPARATUS AND TECHNIQUES

Reactions with sodium in dioxane,--In all reactions employing metal dispersiont (usually molten sodium in dioxane) the apparatus depicted by

Blanchard was used. 48 This apparatus was a Morton high-speed stirring

assembly equipped with a mercury valve system so arranged that gases

generated in the reactions could be collected over brine. The mercury valve system permitted sweeping the system with nitrogen, gave a safety

outlet for excessive pressure in the system, and allowed nitrogen rather

than air to be admitted to the system should the pressure in the system

fall below atmospheric pressure. A 500 ml. Morton flask with two creases

on the sides and an inverted cone on the bottom served as the reaction

vessel. A bent tube through one of the side necks supported a vertical

Vigreux column. A bypass led from the column to the bearing housing of

the stirrer assembly. From the top of the column, a Claisen head and

adapter were attached to a 500 ml. distillation receiver. From the

adapter, tubing led to a 250 ml. flask with side arm, (which acted as a

safety trap) and thence through two 500 ml. extra coarse ftitted glass

scrubbers containing 0.2 to 0.4 N hydrochloric acid (a known number of

equivalents). The purpose of the scrubbers was to remove volatile amines

generated in the reactions so that the yield of volatile amines might be

48Blanchard, op. cit., pp. 36-40. 66

estimated. A tube led from the last scrubber to a ten or twenty liter gas collection bottle, so marked as to enable the volume of gas collected to be estimated. A tube extending nearly to the bottom of the gas collection bottle permitted the withdrawal of samples for analysis. The gas was collected by displacement of saturated brine. It should be stated here that the yields of gas found were not usually quantitative. This was probably due to the fact that the stirrer „yould not be made completely gas tight. By means of moistened Hydrion paper in several runs amine was detected leaking about the shaft. The tendency to leak seemed to increase with continued running of the stirrer. quantitative or nearly quantitative yields were often obtained when the reactions were fast, with a consequently shortened reaction time. The yields in nearly all the reactions were probably quantitative, mechanical losses through leakage about the shaft accounting for the less than quantitative yields observed in the usual case. The experimental techniques employed in the use of the apparatus have been described by . Blanchard. 48 In Technique 1, the apparatus was swept with nitrogen, and while nitrogen passed through the apparatus, solvent, salt, and sodium were added to the Morton flask. A powder funnel was used to aid in the transfer of the salt through the side neck of the Morton flask. The salt had been dried from 24 to 48 hours in the vacuum oven at a pressure of about one millimeter and temperatures of 70-850 . The solvent was heated to boiling in about ten minutes by means of a Glascol heating mantle, the voltage was then reduced and the stirrer was started. It was necessary to start the stirrer at a low voltage 67

until the speed of the reaction could be judged. The stirrer was then usually run at 90-100 volts, since only a few of the reactions were so rapid as to require the stirring to be slow. The time of stirring ranged from less than fifteen minutes to over five hours, depending on the time required for the reaction to reach completion. A reaction was deemed complete when bubbles of gas ceased to pass through the scrubbers.

To ensure completeness of the slower reactions, stirring was continued from ten to fifteen minutes after the last passing of gas bubbles. After the stirrer had been stopped about half of the solvent was rapidly distilled. One hundred twenty-five milliliters of solvent was then added through a dropping funnel in the Claisen head at the top of the Vigreux column and about half the solvent was again distilled. The system was then swept with from six to eight liters of nitrogen (Technique la). Due to the possibility of leakage of gas during the distillation, about half of the sweep gas was sometimes passed through the system before the distillation was begun, and the remainder of the gas after the distillation was complete (Technique lb).

Technique 2 was the same as Technique 1, except that the dioxane and sodium were added first, and no salt was added until a finely divided sodium dispersion had been obtained. The salt was then added in increments through a rubber tube wired to a side neck of the Morton flask and to the neck of an Erlenmeyer flask which contained the salt to be reacted. The rubber tube was arranged so that it could be clamped shut between additions. Each increment of salt was allowed to react until the reaction became sluggish before the next increment was added. 68

Further details concerning the apparatus and techniques are to be found in Reference 48.

Reactions with sodium in liquid ammonia.--The apparatus depicted in

Figure 4 was used for all reactions with sodium in liquid ammonia. This apparatus was adapted directly from the design of Fernelius and

Johnson, 49 with a few simplifications and modifications made during the course of the work. Traps a and c were omitted from the apparatus during some of the work.

The salt to be reacted with sodium in liquid ammonia was weighed in retort n and dried in the vacuum oven at 70-85 ° for overnight or longer. The retort was closed with a rubber stopper and stored over phosphorus pentoxide in a desiccator until the reaction was run. The sodium was weighed in retort o (identical in design to retort n) just before a reaction was to be run. All weighings were done on an analytical balance. The salt retort was usually reweighed after the reaction, since often all the salt could not be added. Sometimes salt stuck in one of the necks of the reaction tube and did not come into contact with the liquid ammonia solution. No correction could be made for this, but since an excess of salt was used in many of the reactions and the yields were therefore based on sodium, yield data were, neverthe- less, usually obtainable.

The procedure for carrying out a reaction in liquid ammonia

(Technique 1) was as follows. Gaseous ammonia was swept through trap

49W. C. Johnson and W. C. Fernelius, J. Chem. Educ.„ 6 , 441 (1929). 1"(

TO ORSAT GAS BURETTE

0 in 19/38 a 500 ml.

Lt.

n 3 ti co

Hg H

30 mm. o.d.

Figure 4. Schematic Diagram of the System Used for Reactions with Sodium in Liquid Ammonia. 70

thence through reaction tube 12, trap c, and mercury valves e and f to collection tube E., which contained saturated brine solution. When all the air had been displaced from the system, the ammonia stream was stopped at the tank valve, and collection tube E. was drained through stopcock h, then refilled with saturated brine solution through stopcock i. During the refilling, stopcock k was closed, and stopcocks i and 31.

j to the stopcock of the Orsat gas were open. The tube leading from burette was filled with brine. When collection tube £ and the tube leading from it were filled with brine, stopcocks i and j. were closed and k was opened. After adding the salt from retort n a slow stream of ammonia was then passed through the system and a dry ice-acetone bath placed about reaction tube be As ammonia began to condense in 1, mercury from valve e rose in tube d. The ammonia stream was increased so that

50 ml. of liquid ammonia (the amount used in the experiments was 50 + 10 ml,) could be condensed in b in 15 to 30 minutes. The column of mercury extended, into tube d during this time. When sufficient ammonia had condensed, the dry ice bath was removed. As the ammonia warmed to its boiling point, qualitative observations concerning the solubility of the salt in liquid ammonia were made. The ammonia stream was reduced gradually during the warming so that a constant slow stream of ammonia gas would bubble through the liquid ammonia so as to prevent bumping when the boiling point had been attained. When the ammonia had come to a boil, the sodium was added by tipping retort o. The sodium blue color was usually discharged in about ten minutes. The hydrocarbon gases generated were collected in B.,0 The ammonia dissolved in the brine, and 71

the brine displaced by the hydrocarbons went into bulb 1. If the brine

in the collection tube Et became saturated with ammonia, fresh brine could be added from bulb a. After the sodium reaction was complete, as evidenced by discharge of blue color or non-evolution of gas, the liquid ammonia was allowed to continue to evaporate slowly. The solution was stirred by a slow stream of ammonia during the reaction and the evaporation. If the room temperature was moderate, the apparatus could be left unattended for as much as two hours, the approximate time required to evaporate the liquid ammonia. The evaporation of the last five or ten ml. of liquid ammonia could be accelerated by surrounding reaction tube b with water contained in a beaker. This had to be done with care, since too rapid boiling caused the whole system to shake and led to heating of the brine in (due to dissolving ammonia), so that it frequently had to be renewed. After all the liquid ammonia had evaporated, the system was swept rather rapidly for a few minutes with gaseous ammonia.

The volume of gas from the reaction was measured in an Orsat gas burette. The transfer from a to the burette was accomplished by opening stopcock j and the stopcock of the burette and raising bulbs g and/or 1 with stopcocks i and/or k open. Gas was thus displaced from a into the burette. Care was taken to displace all the gas from the tube leading from to the burette with brine. About 50 ml. of brine passed to the

Orsat burette in this treatment. The gas was then passed from the burette to an Orsat gas pipette containing ca. 1 N hydrochloric acid in saturated brine s where it was stored while the Orsat confining liquid

(composed of 20 ml. of concentrated sulfuric acid s 105 go of sodium 72

sulfate, and Boo ml. of water) was renewed. The gas was then passed

from the pipette to the burette several times until constant volume was

attained. This volume was the volume of gas evolved in the reaction, with ammonia and amine vapors removed.

Technique 2 was the same as Technique 1, except that sodium was added before the salt. The salt was necessarily added before the ammonia came to boiling, since otherwise extreme bumping occurred and the reaction mixture could not be contained in reaction tube b.

Technique 2 was abandoned after being used in preliminary experiments, since when it was used, appreciable reaction occurred below the boiling point of ammonia. Such premature reaction altered the methane to alkane ratio, since this proved to be variable with temperature.

Less general experimental techniques are described elsewhere in this thesis, in connection with the details of the experiments for which they were used. 73

CHAPTER VI

REACTIONS OF TETRAALKYLAMMONIUM HALIDES WITH SODIUM IN DIOXANE

Reactions of Tetraalkylammonium Halides with Sodium in Dioxane-t-amyl Alcohol Mixtures Blanchard found that with a given quaternary ammonium halide

N(CH3)4_n (n-C4H9) nX (n = 1 to 3), the methane to butane ratio, as measured by his infrared analyses, decreased with decreasing concentration of ammonium salt reacted with a fixed amount of sodium in dioxane- t-amyl alcohol mixtures. 5° Blanchard's observation was shown to have another interpretation in the present work which was undertaken to confirm and extend the earlier report.

n-Butyltrimethylammonium chloride was reacted with sodium in a mixture of 110 ml, dioxane and 140 ml, of t-amyl alcohol. The results of these experiments, undertaken by the techniques of Blanchard, are given in Table 5, It is readily seen that with decreasing amounts of salt taken the butane yields recorded increased to impossible values.

The following possible sources of error were considered in trying to find the source of this difficulty purity of salt used, effect of hydrogen gas on the optical density of butane in the infrared, effect of methane gas on the optical density of butane in the infrared, contamina- tion of product with residual or dissolved gas (from a previous run) in 50 Blanchard, 22a cit., p. 90 74

Table 5. Apparent Results of Reaction of n-Butyltrimethylammonium

Chloride with Sodium in Dioxane-t-amyl Alcohol

Yields (per cent) Moles Sodium Unsaturates Butane Total Methane Amines CH,/C4 4-10 Salt (g.-atoms)

0.0503 0.497 47 21.1 13.8 82 72 1.52

0.0202 0.506 51 2600 42.7 120 82 0.610

0.0103 0.500 56 16.5 ± 2 8205 4- 4.o 155 0.208

0.0109 0.507 56 43.5 137 237 0.287

0.0106 0.561 42.2 42.2 86 170 0.489

aAll yields based on salt taken. 75

the gas collection and analytical systems, end a reaction of t-amyl alcohol with sodium to produce a hydrocarbon product.

Volhard titrations were carried out on samples of the salt used

in the sodium reactions. The per cent chloride found was 23038 and

23.43, which values compare favorably with the calculated value of

23.38 pei cent.

A calibration curve for butane at 6.81 microns for which nitrogen gas was used as diluent had been prepared and used in the butane analyses.

When a check calibration was made for which hydrogen gas was used as a diluent, the points obtained fell on or near the original plot, with a maximum deviation of two per cent.

Partial pressures of methane gas up to 19.0 mm, had no effect on the optical density at 6,81 microns of a sample of butane at a partial pressure of 1202 mm,

The following procedure was carried out to determine the presence or absence of residual gases in the collection apparatus and analytical system. Nine liters of nitrogen was bubbled into the gas collection bottle. Samples were removed to the Crsat apparatus. The samples showed no contraction on treat ent with the mercuric sulfate solution in the Orsat apparatus. After treatment with comet trated sulfuric acid, the samples were transferred, to the gas cell (see Chapter IV) and the sample scanned on the infrared spectrophotometer. The spectrum so obtained was devoid of bands. These results indicated that no impurities were picked up from the collection bottle or analytical system.

Sodium was reacted with t-amyl alcohol and the infrared spectrum of the gas from the reaction taken. Hydrocarbon bands were apparent in 76

this spectrum even after the gas had been treated to remove unseturetes.

The anomalous results obtained for the butane yields above were doubtless

due to this superfluous hydrocarbon. Work done on the reaction of t-amyl

alcohol with sodium will be described in the next section.

The Reaction of t-Amyl Alcohol with Sodium

The obtaining of a hydrocarbon product in the reaction of t-amyl

alcohol with sodium suggests the possibility of a carbon-oxygen cleavage

in this reaction to yield isopentane according to a process such as:

CH3CH2C(CH3 ) 20H Na. slow CH3CE26(CH3 ) 2 NaOH

CH3CH26(CH3 ) 2 Na. _fas t cH3cH2c (cH3 ); + Nal'

CH3CH2C(CH3 ) 2 ROH fast, CH3CH2CH(CH3)2 + RO-

Alternately, a hydrocarbon product might be obtained through a reversal

of the Grignard-type synthesis of alcohols: 51

CH3CH2C (CH3 ) 20Na CH3CH2Na + (CH3 ) 2C0

CH3CH2Na -->C2H6 RONa

A third possibility is that the hydrocarbon product arises from an

impurity in the t-amyl alcohol. Details of the experiments follow:

Reaction of t-Amyl Alcohol with Sodium in Dioxane

Materials.--110 mla dioxa e

140 ml. t-amyl alcohol

11.54 g. sodium

51J. March, Unpublished Ph. D. Thesis, Pennsylvania State University, 1957; Dissertation Abstracts, 22 9 959 (1957). 77

Apparatus and technique,--As described in Chapter V, Technique is

(Dioxane runs).

Procedure,--The stirrer was run for thirty minutes until no more gas was evolved. Two liters of gas was evolved in the first five minutes at which point the reaction slowed markedly; six liters of gas was evolved during the total time of stirring. The system was swept with nitrogen to bring the volume of the gas to 8225 ml, Samples of gas were then withdrawn and discharged to the atmosphere. It was noted that the gas had an olefin-like odor. The volume of gas in a sample was found to contract on treatment with mercuric sulfate and with iodine bromide solution, indicating the presence of unsaturates. Yield of unsaturates was 0,2 per cent on basis of alcohol, or 1.2 per cent based on sodium taken. The infrared spectrum of the gas (unsaturates removed) was compared with spectra of dioxane and of t-amyl alcohol vapors. On the basis of this comparison, dioxane and t-amyl alcohol vapors were definitely eliminated as possible components of the gas mixture. From the optical density at 6.82 microns, the yield of saturated hydrocarbons was crudely estimated to be 006 mole per cent (as isopentane) of the alcohol used, or 2.9 per cent based on sodium. Two g.-atoms of sodium were assumed to be required to produce one mole of hydrocarbon.

Reaction of t-Amyl Alcohol with Sodium, Run 1

Materials.--250 ml. t-amyl alcohol

12.80 grams sodium (0.557 g. -atom) Apparatus and Technique.- As described in Chapter V, Technique is

(Dioxane Runs). 78

Procedure.--The reaction was complete in 43 minutes to give 7300 ml. of gas. Sweeping with nitrogen brought the total volume of gas to 8775 ml.

Infrared spectra of the gases obtained were identical to those obtained for the gases from the previous run, where part of the solvent was dioxane. This result is evidence that the product was probably obtained from t-amyl alcohol and not from dioxane. The yield of saturated hydrocarbon by optical density measurements (as isopentane) was 1.5 per cent based on alcohol or 5.9 per cent based on sodium. The yield of olefins (by contraction with mercuric sulfate) was 106 per cent based on sodium, or 0.2 per cent based on alcohol taken.

Reaction of t-Amyl Alcohol with Sodium, Run 2

Materials.--250 ml, t-amyl alcohol

13,6 g. sodium (0.591 g,-atom)

Apparatus and techniques.--As described in Chapter V, Technique la

(Dioxane runs). The apparatus was modified such that the gas evolved in the reaction did not pass into the gas collection bottle, but instead into a foot long Drierite tube and then through two cold traps arranged in series. These traps were chilled by a slurry of dry ice and acetone.

Procedure.--After the reaction was complete, a few ml, of liquid was found in the first trap, and a few drops in the second. There was no solid material in the traps even at the temperature of the dry ice baths

(-78° ). An infrared spectrum of the vapors of the unknown liquid was obtained as follows. The liquid was poured into a small test tube and connected to one of the stopcocks of the gas handling apparatus. The apparatus was evacuated, the pump stopcock closed, and the stopcock to 79

the test tube was opened slightly, so that the liquid in the tube partially evaporated into the gas handling apparatus. The stopcock to the test tube was closed and the system evacuated; the procedure was repeated several times in order to remove superfluous air from the test tube; and a sample of the vapor was then taken at a partial pressure of

156 mm. at 26° (nitrogen diluent to atmospheric pressure). The sample was then scanned from 2 to 15 microns on the infrared spectrophotometer.

A sample of Phillips Research Grade isopentene vapor (156 mm, partial pressure) was prepared in the same way, and scanned in the same manner.

Comparison of the curves shoved that the unknown liquid was not isopen- tame in whole or in part. A similar comparison with a spectrum of n- pentane vapor (157 mm. partial pressure) showed that the unknown liquid could not be 1-pentane. When the vapor spectrum of the unknown was compared with known spectra, it was found to be most similar to that of

2,2-dimethylbutane. 52 Other spectra compared were those of 2-methylbutene-2, cis-pentane-2, trans-pentene-2, isobutane, neopentane,

11 1-dimethylcyclopropane, ethylcyclopropane, 2-methylbutene-1,

3-methylbuteie-1, and 3,3-dimethylbutene-1.

Reaction of t-Amyl Alcohol with Sodium, Run 3

Materials.--255 ml. t-amyl alcohol

15.1 g. sodium (0.657 g.-atom)

Apparatus and technique.--As in Run 2.

Procedure.--The boiling mixture was stirred for ten minutes, after which

52American Petroleum Institute Research Project 44, Petroleum Research Laboratory, Carnegie Institute of Technology, Frederick D. Rossini, Director. 8o

time the reaction was complete. The system was then swept for three minutes with nitrogen. The unknown liquid was again obtained in the cold trap. The vapor pressure of the unknown liquid was taken as follows: The gas handling apparatus was evacuated and a test tube containing the unknown liquid attached. Superfluous air was swept from the test tube as described above. The system was evacuated and the stopcock to the test tube gradually opened. The test tube was then immersed in a beaker of warm water, causing a sharp increase in pressure, then allowed to cool to room temperature until the pressure reading on the manometer became constant. In this way the vapor pressure of the sample was estimated as 456 mm. Hg at 27.8 ° . For comparison, the vapor pressures of n-pentane and of isopentane were measured in the same way. a-Pentane had a vapor pressure of 541 mm. and isopentane a vapor pressure of 749 mm., each at 27.8 ° . By use of the formula: 53

(273.1 t)(2.8808 - 4.65 + 0.15(2.8808 - log p where 2 is ix mm. and t in °C, the normal boiling point (temperature t at which vapor pressure was measured plusAt) was estimated to be 36.3° 54 ° listed. In the same way, the for a-pentane as compared with 36.1 unknown liquid was estimated to have a boiling point of 42.0 ° C at

53Handbook of Chemistry and Physics, Chemical Rubber Publishing Co., Thirty-first Edition, Cleveland, Ohio, 1949, p. 1831.

54Ibid., p. 987. 81

760 mm., if it is assumed to be a pure liquid. The boiling point of

2,2-dimethylbutane is 49.7°, whilst that of the corresponding unsaturated compound, t-butylethylene, is 41.20 . The liquid could be from the results indicated, a mixture of the latter two hydrocarbons. A definite result of the preceding work is that the unknown liquid does not consist of C5 hydrocarbons, but probably consists of C6 hydrocarbons, at least in part.

The unknown liquid was found to decolorize bromine in carbon tetrachloride and also to decolorize potassium permanganate in acetone.

Procedures were carried out to estimate the proportion of unsaturates is the unknown. A 250 ml, bottle was marked and arranged for collection of gas over brine. Fifty-five milliliters of air was then added. A corked test tube containing the unknown liquid was then maneuvered into the mouth of the gas collection bottle and the cork removed so the unknown would evaporate into the gas already in the bottle. The volume of gas in the bottle increased to 85 ml, and held constant at this volume for 30 minutes, All the liquid appeared to evaporate. The 30 ml. expansion indicates that 0.0012 mole of hydrocarbon evaporated into the bottle. This compares favorably with 0.0014 mole estimated by volume and density considerations for the liquid, with the assumption of a C6 hydrocarbon. Most of the gas from the bottle was transferred to an

Orsat gas burette and analyzed in the usual way. Treatment with mercuric sulfate solution showed that the sample (representative of the 85 ml,) contained 1.75 per cent unsaturates by volume; treatment with IBr solution followed by KOH solution indicated a possible additional 82

content of 0.6g per cent unsaturates. The infrared spectrum of the residual gas was taken in the usual way and the partial pressure of saturated hydrocarbon estimated by extinction coefficients deduced from i the infrared spectrum prepared from the unknown derived from run 2.

These extinction coefficients were for wave lengths 6.85, 7.33, 8.24, and 9.85 microns respectively. The largest value determined differed from the smallest by 16 per cent. By this method the average percentage of saturated gas in the sample was 1504 ± 1,0 per cent. The ratio of saturated to unsaturated material is then 8,8 101 or 6,2 + 0.6, depending whether or not the absorption by IBr is assumed to be due to removal of unsaturates or due to physical solubility of the gas sample.

By the preceding crude analysis, 0000070 mole of gas was determined to be present in the gas evolved by evaporation. This does not compare favorably with the volume and density estimate of 0.0014 mole of liquid, but as the latter depended on crude measurements of the inside dimensions of a small test tube, such an error is perhaps allowable.

The Reaction of t-Amyl Alcohol with Sodium, Run 4

Materials.--700 mlo t-amyl alcohol 2700 g. sodium (1017 g.-atoms)

Apparatus and technique,--As in Rum 2, The 500 ml, Morton flask was replaced by a one-liter Morton flask, Procedure.--The solvent and molten sodium were stirred for eighteen minutes until the reaction seemed complete. After the reaction, as much

iExtinction coefficients were assumed to be about the same, as an approximation, for the unsaturated as for the saturated hydrocarbon. 83

as possible of the solvent was rapidly distilled from the sodium alcoholate. About 4.2 ml. of liquid was found in the cold traps. Vapor pressure measurements were taken as described above, yielding a vapor pressure of 381 mm. at 23.1 ° . The boiling point calculated from this data was 42.0°, which checked the result obtained with the material derived from Run 3. If the material is assumed to be largely t- butylethane„ the yield was 5.4 per cent based on sodium, or 0.5 per cent based on alcohol. The unknown was transferred to a 10 ml. distilling flask and heated with a water bath. The liquid boiled through a continuous range, starting at 42 ° . Considerable material boiled at

47-49.20 , where about three-fourths of the original liquid remained.

At 60 less than one-fourth of the original material remained. It was estimated that three-fourths of the original liquid was gone when a temperature of 53 ° was reached.

The t-amyl alcohol which had been distilled from the reaction was fractionated through a foot-long vacuum jacketed column of two centi- meters diameter packed with eighth-inch glass helices. With a reflux ratio of 4:1, a forerun of about 20 ml, boiled et 88.5-101.7 ° . Addition- al forerun boiling 101.0-101.7 ° was obtained at a reflux ratio of 60:1 0 during a two hour period. The main fraction boiled at 101.7-102.1

(principally 101.7-101.8 ° ) at a reflux ratio of 2:1. The pressure during the distillation was 743.1 mm, Two hundred sixty-two milliliters of the t-amyl alcohol from the main fraction was reacted with 12.5 grams of sodium in the usual way. Liquid amounting to 0.6 ml. was found in the cold trap, a yield of 1.7 per cent as t-butylethane, based on sodium or

0.19 per cent based on alcohol taken. "Boiling points" estimated from vapor pressure measurements were 4407 and 4304 ° respectively, indicating that the unknown mixture was of different composition from that obtained earlier with unrecycled t-amyl alcohol. The infrared spectrum of the vapor of the unknown was similar to that obtained with the earlier unknowns, but the relative heights of the bands were different, indicating a mixture in different proportions.

Significance of Results

The hydrocarbon mixture obtained as a byproduct in the reaction of t-amyl alcohol with sodium was shown not to be isopeatene, eliminating the possibility of a reductive cleavage of the carbon to oxygen bond in t-amyl alcohol. Infrared, vapor pressure, boiling point, and chemical data favor a mixture of C6 (or higher) hydrocarbons containing 12-17 per cent ussaturates. The hydrocarbon mixture was evidently derived from impurities in t-amyl alcohol. These impurities must react, but at a rather slow rate, with sodium to give the volatile hydrocarbons.

Furthermore, the impuritie(s) must have boiling points close to that of t-amyl alcohol, as they are not separated by fractionation. The fact that the recycled t-amyl alcohol gave an unknown liquid product mixture of somewhat different properties from the unrecycled alcohol is evidence that the unknown does not arise from the alcohol itself, although the latter possibility has not been rigidly excluded. No further work was done on this problem after this conclusion had been reached, as the problem of identifying the impurities in t-amyl alcohol was seen to be beyond the scope of this thesis. The net result of this work for purposes of this thesis was to show that commercial t-amyl alcohol, even 85

though purified by treatment with highly dispersed sodium and carefully

fractionated, invalidated the results of experiments in which it was

used as a hydrogen donor due to strong interference with the estimation

of butane in the infrared. Use of the dioxane-t-amyl alcohol solvent mixture was consequently abandoned; dioxane alone was found to be an adequate hydrogen donor in most cases in the reaction of quaternary ammonium salts with sodium.

The Reaction of t-Butyl Methyl Ether with Alkali Metals

Introduction

The reaction of t - butyl methyl ether with alkali metals was examined in a preliminary manner as an adjunct to this study. Allyl alcohols are known to undergo reductive cleavage with alkali metals to give propylene.55 Allyl ethers similarly give propenyl potassium on 56 57 treatment with alkali metal. Y Allyltrimethylammonium chloride is cleaved by sodium in dioxane to give propylene in a yield of 22.3 per cent and methane in a yield of 6.4 per cent, that is, allyl groups cleave from quaternary nitrogen about three times as fast as methyl groups. 58 As described later in this thesis, t-butyltrimethylammonium iodide was found to cleave when reacted with sodium in dioxane to produce

55A. J. Birch, uaterly Reviews, 4, 69 (1950).

56A. A. Morton, E. E. Magat, and R. Y. Letsinger, J. Am. Chem. Soc., 69 950 (1947).

57R. L. Letsinger and J. G. Markham, J. Am. Chem. Soc., 70, 3342 (1948).

580ordon, E. cit., p. 124. 86

36 times as much isobutane as methane. From the above data the cleavage

of t-butyl methyl ether by alkali metals might be expected to occur

readily since it may be inferred that a tertiary butyl group is cleaved

from quaternary nitrogen about twelve times as fast as an allyl group

and allyl ethers are known to be cleaved by alkali metals. 562 57

The Reaction of t-Butyl Methyl Ether with Sodium in Liquid Ammonia

Materials.--40 ml, liquid ammonia

0.1195 g. sodium (0,005196 g.-atom)

5.0 ml, t-butyl methyl ether (00043 mole)

Apparatus.--As shown in Chapter V, Figure 4. Retort a was replaced by a rubber stopple such that the ether could be added by syringe and needle.

Procedure,--The technique used was the same as Technique 1 for liquid ammonia reactions described in Chapter V, except that the material to be reacted, t-butyl methyl ether, was introduced by syringe through a rubber stopple. Also, the liquid ammonia was kept from evaporating for

31 minutes by keeping the ammonia somewhat below its boiling point by repeated applications of the dry ice bath. The ether did not appear to be miscible with the liquid ammonia solution; it formed a colorless bottom layer under the blue solution. Some white crystals were seen in

the ether layer before the ammonia was allowed to evaporate. The

identity of these crystals is unknown; t-butyl methyl ether was shown

not to freeze at dry nee temperature. There was very little metallic

sodium remaining after the ammonia had evaporated. The sodium may have been converted catalytically to sodamide. The gas in the collection

tube was analyzed in the usual manner (Chapter IV). A value of 5,8 + 0.3 87

per cent yield of unsaturates was found based on the sodium taken. This yield of "unsaturates" may very well have been due to t-butyl methyl ether vapor present. Casual observations in the laboratory have led the writer to believe that t-butyl methyl ether vapors are absorbed by the mercuric sulfate solution used in the analytical procedure. The infrared spectrum of the residual gas after treatment with concentrated sulfuric acid showed a medium band at about 30455 microns, with no other obvious bands. Optical density measurements indicated a 0.85 -1- 0.04 per cent yield of product calculated as isobutane and based on sodium. It should be pointed out that any material containing C-H, and/or C-CH 3 bonds will give strong absorption in the infrared near 3.46 microns, with the other bands in the region of 2 to 15 microns being relatively much weaker.

Therefore, the band observed could just as well have come from a trace of t-butyl methyl ether vapor as from isdbutane. Qualitative comparisons with infrared spectra of isobutane and of t-butyl methyl ether are inconclusive. Since the analytical procedure employed is known to remove t-butyl methyl ether vapor, isobutane is favored. The low yield may be due to the immiscibility of the ether with liquid ammonia.

Reaction of t-Butyl Methyl Ether with Sodium in Dioxane

Materials.--250 ml. dioxane 35.7 ml, t-butyl methyl ether (0.31 mole)

0050 g.-atom sodium

Apparatus.--As described in Chapter V.

Procedure.--The technique employed was analogous to dioxane Technique 2,

except that the material to be reacted, t-butyl methyl ether, was added 88

through a dropping funnel at the top of the column. The initial addition of ether caused a lowering of the boiling point of the reaction mixture such that the sodium solidified. Some of the ether was distilled out until the sodium again melted. Stirring was again started and the ether added dropwise over the course of 49 minutes; the sodium again solidified, necessitating that the reaction be stopped. The system was swept with nitrogen and the gas collection bottle sealed. Analyses were carried out two days later. The infrared spectra showed that the gas in the collection bottle contained t-butyl methyl ether vapors and no other organic material; no trace of isobutane or isobutene could be found.

The Reaction of t-Butyl Methyl Ether with Sodium in Cumene

Materials.--240 ml, cumene

35 ml, t-butyl methyl ether (0.30 mole) 15.1 g. sodium (0.656 g.-atom)

Apparatus.--As in preceding run. A thermometer well with standard taper joint was fitted in one neck of the Morton flask.

Procedure.--The solvent was brought to about 106 ° as read on the thermometer in the thermometer well. The stirrer was run for a short time until the sodium became finely dispersed. All of the ether was added over the course of about 10 minutes, with the stirrer off. The pot temperature went down to 92 ° as a result of the addition of ether. When the pot temperature was 102°, the stirrer was started at a setting of

120 volts, somewhat higher than usual. Stirring was carried out for two hours, with two short interruptions for tightening the stirrer shaft.

One hundred eighteen milliliters of t-butyl alcohol was added and the 89

stirrer speed decreased. The latent formation of a cake of alkoxide threatened to interfere with stirring, but this did not occur. The system was swept with four liters of nitrogen and the analysis carried out. The infrared spectrum of the gas which had been treated to remove unsaturates showed only a rather weak band at about 3.45 microns.

Optical density measurements indicate a yield of 0.037 per cent as isobutane based on sodium. As in the previous run, it should be pointed out that this single weak baud in the infrared was the only evidence that a reaction had occurred, and this evidence is indefinite for reasons cited in the account of the previous run in liquid ammonia.

The Reaction of t-Butyl Methyl Ether with Potassium in Dioxane

Materials.--250 ml. dioxane

30.2 ml. t-butyl methyl ether (0.26 mole)

22.2 g. potassium (0.568 g.-atom)

Apparatus.--As in the preceding runs. The thermometer well was not used.

Procedure.--The potassium was cut in a nitrogen-swept dry box and transferred to the Morton flask while wet with kerosene. The stirrer was run at about 70 volts; all the ether was added over a period of half an hour.

The potassium did not become well dispersed. After an hour, the stirrer speed was advanced; some gas was apparently evolved, but this may have been expansion due to distillation of the ether. Since the potassium was still not well dispersed after two hours of stirring, 0.9 g. stearic acid in 25 ml, of dioxane was added to the mixture. This addition, however, had no effect on the dispersion. Half an hour later 15 ml. of

10 per cent by volume oleic acid in dioxane was added. The potassium 90

became better dispersed, but particles were still large enough to be

readily visible. An hour later, when the connection between the stirrer

shaft and the shaft of the electric motor failed, the reaction was

stopped. The system was swept with nitrogen and the gas collection bottle sealed. Analysis was carried out on the following day. Only

one very weak band at 3.455 microns (optical density 0.019) was present

in the gas treated for removal of unsaturates. The yield as isobutane was 0.012 per cent based on t-butyl methyl ether.

The Reaction of t-Butyl Methyl Ether with Potassium in Tetrehydrofuran

Materials.--255 ml. tetrahydrofuran

20.7 ml. t-butyl methyl ether i (0.17 mole)

31.1 g. potassium (0.794 g.-atom)

Apparatus.--As for dioxane runs, above.

Procedure.-the stirrer was run. at 80-95 volts. The potassium dispersed well in the tetrahydrofuran solvent. The ether was added over a six minute period. After an hour, there was no evidence of reaction; the dispersion was greenish gray. A solution of 0.1 g. anthracene in 15 ml.

of tetrahydrofuran was added. A transitory blue color was observed at

the point of first contact of the solution with the reaction mixture.

Very soon the reaction mixture became red-brown, darkened through brown,

then green brown, and finally after 24 minutes became forest green. The

liquid forced up somewhat into the side arm showed a fleeting orange

color. Thirty-four minutes after the addition of anthracene, the

iThe t-:butyl methyl ether was recovered from the previous dioxane run and had a boiling point of 56-69°. 91

material became blue-green, and by 20 minutes later the reaction mixture was deep blue. t-Butyl alcohol was then added to the reaction mixture.

The first milliliter added brought the color back to reddish-brown, and

the second to the gray color the mixture had before the anthracene was added. The rest of the alcohol (sufficient to destroy the potassium) was added slowly at first, with intermittent stirring, then all at once.

The time to add the alcohol was about one hour. The system was swept with four liters of nitrogen. The next day the analysis was performed.

In the infrared spectrum of the gas treated for removal of unsaturstes there was no evidence for the presence of a hydrocarbon or any other organic material.

Discussion of Results

t-Butyl methyl ether was subjected to reaction with sodium or potassium under a variety of conditions. All results obtained were inconclusive. The best evidence that t-butyl methyl ether reacts with sodium to give isobutane was with sodium in liquid ammonia. Weaker evidence VAS obtained for the reaction when sodium in cumeate or potassium in dioxane was employed. Difficulties in carrying out the reaction were: the immiscibility of the ether with liquid ammonia, solidification of the sodium in the sodium-dioxane mixture, poor dispersion ability of potassium in dioxane, and distillation of most of the volatile ether from the reaction mixture when dioxane or cumeate was used. The tetrahydrofuran solvent offers none of the difficulties mentioned, but no reaction could be observed in this medium. The results indieate that although it may be possible to cleave t-butyl methyl ether to give 92

isobutane by means of alkali metal, this reaction does not occur readily, probably due to a high activation energy for the reaction. The liquid ammonia medium appears to be the most suitable for further work; use of this medium at higher temperatures (pressure apparatus) and higher concentrations of sodium is suggested.

Reactions of Tetraalkylammonium Halides with Sodium in Dioxane

In order to determine the relative abilities of certain alkyl groups to cleave, a number of quaternary ammonium halides were reacted with sodium in dioxane. A few of these reactions were carried out before the analytical procedure described in Chapter IV had been completely worked out. The procedure of analysis for these early reactions was similar to that described in Chapter IV, except that optical density measurements were made for butane at 6.81 microns. Concentrations of methane encountered in this work were assumed not to absorb at this wavelength. The concentrations of butane encountered, however, were such as to give a very low optical density reading at 6.81 microns; consequently, the error in determining butane was large, and the results were of little value for determing the relative abilities of methyl and butyl groups to cleave. The data found are given in Table 6. All yields given are based on salt taken.

The results of the reactions carried out with the analytical technique described in Chapter IV are listed in Table 7. All yields given are based on salt taken. A methane to alkane ratio in general was accepted only when the results of two different runs agreed within the error estimated for the analyses. Table 6. Results of Reactions of Tetraalkylaznmonium Halides with

Sodium in Dioxane

(Preliminary Runs)

Salt Reacted Run Salt Sodium Reaction ------Yield, per cent ----- Ratio No. moles g.-atams Time, min. CH4 Alkene Alkane CH./Alkane n-Bu 1 0.0863 0.498 16 17 3.0 19 + 3 3 MONIa 55.7 n-BU3MeNI 2 0.0449 0.503 32 60.7 27.2 4.2 15 + 2 n-Hu3MeNI 3 0.0221 0.507 -- 39.3 9.3 2.5 16 + 4 n-Bu3menleb 1 0.0995 0.507 8 36.9 31.5 4.3 8.6 + 0.5 n-Bu3MeNBrb 2 0.0559 0.500 3 45.8 33,8 6.7 7.0 ± 0.5 n-BUNIe3=1 1 0.110 0.505 47 23.5 13.5 0.50 47 n-BUMe3HC1 2 0.1036 0.501 62 37,2 28.2 0.46 81 n-BUMe3NC1 3 0.1077 0.497 42 32.0 28.6 1.5 21 n-BUMe3NC1 4 0.1054 0.503 51 42.0 31.7 1.0 42

aReaction mixture foamed and was carried into receiver, where it continued to react. Methane to alkane ratio is therefore not comparable to others.

bThe methane analysis for this run was made on a high optical density portion of the calibration curve where the curvature increased sharply approaching a vertical asymptote and in a region where the spectrophotometer was said to be non-linear. Hence the value of the ratio given may be considerably more in error than indicated. \43 Coo Table 7. Results of Reactions of Tetraalkylammonium Halides with Sodium in Dioxane

Salt Run Salt Sodium Reac, Yield, per cent ------Ratio Reacted No. moles g.-atoms Time, Volatile CH4/Alkane min. Amine Alkene CH4 Alkane

n-Bu3MeNIa 4 0.0911)1 0.487 3 11.4 52.4 + 1.1 2.28 + 0.04 23.0 + 0,5

n-Bu MbNIb 5 0.101 0.491 18 22.0 + 0.7 55.5 + 1.4 3.13 + 0.08 17.8 + 0.5 3 n-Bu3mear 3 0.1006 0.534 8 35.0 + 0.8 45.3 + 1.9 2.91 + 0.04 15.6 + 0.7

n-Bu 3 MaNBr 4 0.0961 0.530 lo 37.0 + 0.8 51.8 + 1.6 3.36 + 0.04 15.5 + 0.4 t-BUMegIc 1 0.1006 0532 143 84.0 7.6 + 0.8 1.23 + 0.15 65.2 + 2.7 0.0188 + 0.0022

t-BuMe3NI 2 0.1094 0.474 173 5.3 + 0.7 1.36 ± 0.08 50.1 + 1.4 0.0272 ± 0.0018

t-BUMe3BI 3 0.1013 0.544 100 48.8 5.5 + 0.8 1.20 ± 0.12 41.9 + 1.0 0.0287 + 0.0026 s-BUMe3NI 1 0.1001 0.509 54 30.9 13.7 64.2 + 3.2 10.8 + 0.3 5.93 + 0.30 s-BuMe3NI 2 0,0946 0.526 7 26.8 14.6 + 0.8 62.1 + 1.4 9.72 + 0.22 6.40 + 0,20

s-BUMe3NI 3 0.07605 0.478 15 37.1 19.2 + 1.0 66.5 + 1.5 12.1 + 0.20 5.51 + 0.14

n-BUMe3NI 1 0.103 0.526 11 23.6 21.5 + 1.1 67.0 + 1.9 0.698 + 0.028 95.9+ 4.6

21-BUMe3NI 2 0.101 0.504 14 21.4 17.3 + 1.0 73.7 + 1.5 0.686 + 0.027 107.4 + 4.6

n-BUMe3NC1 5 0.111 0.496 60 33.8 30.2 + 1.4 37.8 + 0,9 0.537 + 0.037 70.3 + 5.0 n-BUMe3NC1 6 0.113 0.500 8o 28.1 25.3 + 1.4 33.8 + 0.7 0.356+ 0.028 94.9+ 7.6 n-BuMe NC1d 7 0.1080 0.543 62 25.6 23.8 + 1.3 109.8 + 11.6 3 33.3 + 0.8 0.305 + 0.033 n.'PrMe3NI 1 0.0899 0.461 14 32.5 28.0 + 0.7 57.3 + 1.3 0.434 + 0.043 133 + 13 Table 7 (continued)

Salt Run Salt Sodium Reac, per cent------Ratio Reacted No. moles go-atoms Time., Volatile CH4/Alkane min. Amine Alkene CH4 Alkane n-PrMe3NI 2 000815 0,513 10 3108 27.4 + 105 55.9 + 109 00474 + 00050 118 13 i-PrMegi 1 0.0973 0539 13 21,0 9.2 + 0,9 80.2 + 2,0 7,83 + 0.24 1002 ± 0,39 i-PrMe 2 0,0987 00496 17 27.6 6,5 + 008 5107 + 1.6 4091 ± 0,25 10.5 + 0,62 3 NI Et3MeNI 1 0.1162 0,561 15 8.40 901 + 1,3 8400 + 1.8 9.97 ± 0.09 8.40+ 0.20

Et MeNI 2 0.1045 00543 12 - 8,3 + 1.5 8800 + 3. 14. 10.1 ± 0.14 8067 + 0034 3 Et3MeNCle 1 0.0914 0.533 73 23.5 48.7 + 106 2208 + o.46 4.17 + 0.24 5.47 + 0.32

Et f 2 0.1071 0.488 51 6603 + 109 18.4 + 0.3 4072 + 0012 3.91 + 0012 3MeNC1 Et h 3 000724 00517 24g 73.2 5704 ± 109 26,2 + 005 3,66+ 0006 7,18 ± 0021 3MeNC1 Et3MeNC1 4 0.09400 0.50o 17 71.8 49.5 + 1,8 23,4 + 0,47 3.40 + 0,07 6090 + 0020 EtMe3NBr 1 0.1004 00500 63 61.4 3408 ± 1.4 57.5 + 205 00798 + 00056 72.1 ± 5.9

EtMe3NBr 2 000965 0517 99 6202 3906 ± 106 52,3 + 105 00649 + o.o65 8o05 + 806

aSee footnote (a) of Table 6. bMethane to alkane ratio for this run is considered to agree with the ratios obtained for Runs 2 and 3 of m-Bu3MeNI in Table 6. Value for this run is considered to be the best determined of the three runs. cRatio from this run not considered valid. Table 7 (continued)

hesults given are the average of two separate analyses. A third analysis, which was discarded, gave a methane to butane ratio of 73.2-4.2. e The analysis of the products of this run was delayed 20 days.

(Value of methane to ethane ratio was not accepted in view of the results of the next two runs. grield given is "total" amine.

hA check analysis of the products of this run gave a methane to ethane ratio of 7.06°0.30. 97

The results of some of the runs were discarded for another reason.

It sometimes happened that a reaction would be so rapid as to cause foaming of the reaction mixture and consequent "boiling over" into the distillation receiver of the apparatus. The material would continue to react in the receiver at a lower temperature than the mixture in the reaction flask. Since the methane to alkane ratio is affected by temperature (as will be established below), the methane to alkane ratio found was different from that obtained when the reaction VAS carried out in the normal way. Dioxane Technique 1 was used for all the reactions the results of which are listed in Tables 6 and 7. Some reactions, the data for which are not adequately covered or do not logically belong in

Tables 6 and 7, are described in the following sections.

The Reaction of Tetra-n-butylammonium Bromide with Sodium in Dioxane

Materials.--250 ml, dioxane

0.0934 mole salt

0.495 g.-atom sodium

Apparatus.--As described in Chapter V.

Procedure.--Dioxane Technique 1 was used. The reaction was quite vigorous, requiring that the stirrer be run rather slowly. The reaction appeared complete after three minutes stirring time. The reaction mixture was a deep blue, probably due to Wurtz sodium bromide. The system was swept with six liters of nitrogen and the gaseous hydrocarbon mixture examined by the usual analytical procedure. Yields were butane, 4602 per cent, and butene, 33,9 per cent. Acetylene was detected in the infrared spectrum of the gas sample which had not been 98

treated for removal f unsaturates. This cffords evidence that acetylene does not arise from the salt reacted, but from some other source, probably the dioxane solvent.

The Reaction of Tetraethylemmonium Bromide with Sodium in Dioxane

Materials.--250 ml. dioxane

0.1009 mole salt

0.496 g.-atom sodium

Apparatus.--As described in Chapter V.

Procedure.--Dioxane Technique 1 was used. Large chunks of the salt were not readily broken up by the stirrer. Caution was therefore exercised and the stirrer run slowly (just above stalling speed) for about en hour.

The stirrer was then run at high speed for another hour, at which time the reaction appeared complete. The system was swept with five liters of nitrogen. Yields were: total amine, 80.0 per cent; alkene, 52.0 +

1.2 per cent; ethane, 35.0 + 1.2 per cent. A sample of ethylene was made up in a gas cell to correspond to the proportion of unsaturates found in the gas from the reactio and placed in the reference beam of the infrared spectrophotometer. A sample cell containing the hydrocarbon- nitrogen mixture from the reaction was prepared in the usual way and placed in the sample beam, and the spectrum taken. In this way, ethylene bands were subtracted from the spectrum of the sample, and the region (9.3-13.5 microns) where one might expect to find butene bands was rendered available to examination. No butene was detected; this is en indication that intermolecular alkylation (as proposed above for methylammonium halides) does not occur so as to involve ethyl groups

(and by analogy, higher groups) in the reactions studied. 99

The Reaction of Tetramethylammonium Bromide with Sodium in Dioxene

Materials.--250 ml. dioxane

0.1029 mole salt

0.5078 g.-atom sodium

Apparatus.--As described in Chapter V.

Procedure.--Dioxane Technique 1 was used. After a stirring time of one hour, the stirrer was stopped and the system swept with two liters of nitrogen; stirring was then resumed at maximum speed. Three hours after starting the reaction, the stirrer was again stopped, and the system swept with two liters of nitrogen. The reaction mixture was a pronounced gray at this point. At five hours, the reaction mixture was purple, and at six hours a blue gray. Seven hours after starting the reaction, the stirrer was stopped and the system swept with nitrogen.

The solvent was distilled in the usual manner.

Yields, based on salt taken, were total amine, 4807 per cent, including 0.44 per cent ethyldimethylamine and a trace of vinyldimethylamine (as determined by a Hoftann exhaustive methylation and pyrolysis procedure); 4704 per cent methane; and 6.1 -0- 1.2 per cent ethylene

(reported as twice mole per cent obtained). The reaction had previously been carried out by Gordon with similar qualitative results with respect to the hydrocarbons evolved. 1

Side Reactions

Infrared bands corresponding to the strongest absorption maxima of ethylene and acetylene at 10054 and 13.71 microns respectively were detected in the infrared spectra of the gases from many of the reactions studied.

100

The following salts apparently gave ethylene when reacted with

sodium in dioxane: tri-n-butylmethylammonium iodide, t-butyltrimethyl-

ammonium iodide, sec-butyltrimethylmmmonium iodide, n-butyltrimethyl-

ammonium chloride, n-propyltrimethylammonium iodide, isopropyltrimethyl-

ammonium iodide, and tetramethylammonium bromide. The ethylene amounted

in most cases to no more than a one or two mole per cent of the salt

taken. It was considered to arise by an intermolecular alkylation

process involving the methyl groups, followed by Hofmann type elimina-

tio : 59

(CH3)4NBr + 2Na CH; + 2Na+ + Br + (CH3) 3N

CH3 + CH3N(CH3 ) 3Br— CH4 + EH2N(CH3 ) 3Br

5H2N (CH3 ) 3Br + (CH3 )41iBr — CH3CH2N (CH3 ) 3Br + (CH3 ) 3N + Br

CH3CR2N(CH3 ) 3Br + B = CH2=CH2 + (CH3 ) 3N + Br + BH.

An infrared absorption maximum corresponding to a trace of

acetylene was observed for the hydrocarbon gases from reactions of the

following salts with sodium in dioxane: tetra-n-butylammonium bromide,

tri-n-butylmethylammonium iodide, tri-n-butylmethylammonium bromide, t-

butyltrimethylammonium iodide, sec-butyltrimethylammonium iodide, n-

butyltrimethylammonium iodide, n-butyltrimethylammonium chloride, n-

propyltrimethylammonium iodide, isopropyltrimethylammonium iodide,

triethylmethylammonium iodide, ethyltrimethylammonium bromide, and

tetramethylammonium bromide. The acetylene observed is considered to

originate from the dioxane solvent by eliminative cleavage reactions:

59Gordom, ok. cit., p. 260

101

- CH2-CH2 , CH=CH 2 - R + 0 + 0/ /0 \ CH2-CH \CH2-CH2

,CH=CH2 9112-0- 0 0" + HCECH + CH2-0 + RH. \ CH2-CH‘

The acetylene "yield" was indeterminate, but when detailed infrared

semi-quantitative procedures were carried out, it was estimated by

difference to be less than one per cent of the salt used

In all the reactions of quaternary ammonium salts reacted with

sodium in dioxane, 1-alkenes corresponding to the alkyl groups of the

salts were found. Evidence for some 2.4) .ute e was also found in the

reaction of sec-butyltrimethylammonium iodide with sodium in dioxane.

These products may all readily be explained on the basis of a Hofmann-

type elimination reaction; the carbanions generated in the reactions

possibly serve as the base:

R- + RCH2CH2/1 (CH3 ) 3X-4- RH + RCH=CH2 + (CH3 )3N + X - .

Other bases in the reaction mixture which could also serve to cause the

CH=CH2 / - /°- /0- elimination are 0 0 and/or CH2-CH2, postulated above. \ CH2-CH

Total unsaturate yields for the reactions are given in Tables 5,

6, and 7. In Table 8, the relative proportions of unsaturates estimated

from optical densities in the infrared (detailed procedure outlined in

Chapter Iv) are given. 102

Table 8. Alkene Product Yields from the Reactions of Quaternary Ammonium Halides with Sodium in Dioxane

Salt Run ------Yieldsa, Per Cent No. Alkene-1 Butene-2 Ethene Ethyne

II-Bu3MeNI 4 10.4 none 1.2 0.5 L-RaMe3NI 1 4.6 none 2,1 0.4 + 1.2 t-BuMegI 2 1.8 ± 0.2 none 2.0 + 0.2 1.4 4, 1.1 t-BUMegI 3 3.0 none 1.3 1.3 + 0.8 s-BUMe3N1 1 6.9 5.2b 1,8

s-BUMegI 3 11.8 5.3b 2,2 NM U. S.1 n-BuMe3NI 1 20.2 none 0.71 n-BUMegI 2 6.6 none 0.74 am CO ill

aAll yields based on salt.

brields by difference, namely total alkene less ethens yield. 103

The Reaction of t-Butyltrimethylammonium Iodide with Sodium in Cumene

22PEREst.--t-Butyltrimethylammonium iodide was reacted with sodium in

cumene in order to detect the possible presence of t-butyl free

radicals. According to Bryce-Smith, the isolation of dicumyl from such

a reaction mixture is evidence for free radicals as intermediates in

the reaction. 60

Materials.--250 ml. cumene

0.1012 mole of the salt

0.500 g.-atom sodium

Apparatus.--As described in Chapter V. A thermometer well was used in

one arm of the Morton flask is order to record the temperature of the

reaction mixture.

Procedure.--Dioxame Technique 1 was used. The temperature ranged from

96.5 to 115° during the eight and one half hours the stirrer was run.

The temperature was below 100 ° for only eight minutes of the stirring

time. The system was swept with about two liters of nitrogen 100 minutes after starting the stirrer, and the stirring continued. The

reaction mixture was a pale gray, with the sodium very finely dispersed.

The usual analytical procedures were employed to determine the hydro-

carbon and amine yields. The flask residue was allowed to stand over-

night and was siphoned into another flask. The mixture was then sub-

jected to vacuum filtration through a fritted glass filter in a nitrogen

atmosphere. The nitrogen atmosphere was maintained by means of a

polyethylene bag which surrounded the filtration apparatus. One-tube

6oP., Bryce-Smith, J. Chem. Soc., 1712 (1955); ibid., 1603 (1956)• 104

led into the bag from a nitrogen tank and a second tube from the side- arm of the filtration flask led from the bag through a cold trap to a vacuum pump. The valve of the nitrogen tank was opened such that the polyethylene bag maintained an inflated appearance. The filtration took about three hours. The light-amber filtrate was washed with 100 ml. of concentrated sulfuric acid, then with three 100 ml, portions of water, and was dried 30 minutes over Drierite. The material was filtered through glass wool and was dried over magnesium sulfate overnight.

Filtration through glass wool gave a clear, colorless filtrate. The filtrate was arranged for distillation from a three-necked 250 ml. flask through a foot-long glass helix packed column. The excess filtrate was added to the flask from a dropping funnel at about the same rate as the liquid distilled. The material distilled principally from

147-148.5 ° . When the volume of liquid residue reached 45 ml., it was transferred to a 100 ml, flask and heated in a nitrogen atmosphere by a silicone oil bath. The distillation of liquid ceased at an oil bath temperature of 205 ° . The residue was 10 ml., or less of an amber colored liquid. A white, apparently crystalline material appeared when 15 ml, of anhydrous methanol was added. This material proved to be intractable to filtration, however. The oily crystals and filtrate were transferred to a 50 ml., flask with the aid of some cumene washings, the methanol stripped off with the aid of a water pump, and most of the solvent removed with heating under water pump suction. A vacuum sublimation at

182° gave a yellow semi-solid as sublimate. There was a nearly solid residue which would not sublime in four hours at 0.02 mm. and 150 ° .

The sublimate amounted to 0.187 g. of oily crystals. Sublimation of 105

this material for four hours at 114° and 0.02 mm. gave 0.055 g. of oily crystals (there was heavy mechanical loss, since the material was isolated by scraping). There was a yellow greasy residue. Some of the resublimed material was crystallized from about 0.5 cc. of absolute ethanol. About seven milligrams of somewhat oily crystalline material was obtained, of melting point 109.4-1112 corrected; melting point of pure dicumyl, 118, 5. 60 Other attempts to get non-oily crystalline material by the use of absolute ethanol also failed. The crystals and oil were both found to be quite soluble in n-pentane. An infrared spectrum of the "recrystallized" material was obtained by means of the potassium bromide pellet technique. The spectrum was not in disagreement with the possibility of dicumyl. Yields, on the basis of salt taken, were: "dicumyl", 1.54 per cent (maximum); isobutane, 17,1 +

0.48 per cent; methane, 0.96 + 0.091 per cent; unsaturates (isobutene),

10.8 + 0.9 per cent; volatile amine, 26.4 per cent. 106

CHAPTER VII

THE REACTION OF TETRAAIKYIAMMONIUM HALIDES WITH

SODIUM IN LIQUID AMMONIA

Initial experiments.--Products of the reactions of tetraalkylammonium halides with sodium in liquid ammonia were analyzed in rather a crude way at first. The analysis of the products of salts bearing methyl and n-butyl groups as substituents was such that there was a large error in the determination of butane, which was generated in even smaller amounts than in the comparable dioxane runs (cf. Chapter VI).

The absorption of butane at 6.81 microns was too small for a good estimation of the butane yield to be made. Furthermore, liquid ammonia Technique 2 (Chapter V) was used for most of the reactions such that results were non-reproducible. Data obtained from the reactions so run and analyzed are presented in Table 9. Experiments la ammonia It2hnique 2.. After it had been determined that tetraalkylammonium halides did indeed react readily with sodium in liquid ammonia, the infrared analytical technique detailed in Chapter

IV was developed. Some more reactions of quaternary ammonium halides with sodium in ammonia were carried out by use of ammonia technique 2.

The analyses of the products of these reactions were carried out by this analytical technique. The results of these experiments are set forth in Table 10. Since the salt was added at variable and unknown temperatures below the boiling point of liquid ammonia, the results Table 9. Products from Reaction of Tetraalkylammonium Halides with Sodium in

Liquid Ammonia According to Preliminary Procedures

Salt Run Salt Sodium Reac. --Yield, per cent-- Ratio No moles g.-atoms Time, CH4/CnI121142 min. CR4 Alkane Alkane n-Bu3MeNBrb 1 0.002537 0.005348 6 57.4 1.6 1 36 ± 4 n-Bu MeNBre 2 0.003297 0.005787 1 1.9 0.09 20 ± 20 3 75 n-BUMe3Nd3 1 0.003372 0.005691 9 84.7 0.80 200 92 ± 23 n-BuMe NC1C 2 0.003177 0.005622 89.5 0.93 2.1 3 9 93 ± 23 n-BuMe3NC 1b 3 0.002468 0.006043 lo 95.7 0.75 ___ 144 + 72 n-BUMe3NClb 4 0.0008706 0.00553 4 04.4 0.95 0.85 8o + 4o n-BuMe b 0.003173 0.265d __ 3Nei, 5 27.6 2.1 13 n-BuMe3NI 1 0.002995 0.005413 8 69.1 2.4 4.7 30

aSodium was added before liquid ammonia had come to its boiling point. Technique 1 was used for this run only. Technique 2 was used for the rest of the runs in this table. by fields based on salt.

cYields based on sodium,

4Copper colored liquid ammonia solution, Table 10. Results of Reactions of Tetraalkylammonium Halides with Sodium in Liquid Ammonia, Technique 2

Salt Run Salt Sodium Reac, Yield Yield Yield Ratio No. moles g.-atoms Time, 14 Alkane Alkene CH4/C nH2n4.2 min. a n-Bu MeNBr 4 0.003170 0.005861 6 89.7 + 0.8 1.25 + 0.02 4.8 + 0.3 71.8 + o,8 3 a 227Bu MeNI 2 0.003089 0.005183 9 86.5 + 2.7 1.4 ± o,o6 5.8 + 0.4 60 + 5 3 n-BuMe3NIa 2 0.003036 0.005035 4 82.7 + 2.8 0.26 + 0.03 1.3 + 0.3 309 + 37 a n-BUMe NI 3 0.002955 0.005261 7 87.1 + 1.6 0.28 + 3 0.12 0.9 + 0.3 311 + 144 a n-BUMe3NI 4 0.002890 0.005191 6 69.6 + 1.0 0.26 + 0.03 0.8 + 0.2 262 + 25 a n-BUMe3 NI 5 0.002515 0.00472 8 95.2 + 1.6 0.28 + 0.04 0.8 + 0.3 342 + 47 t-BuMe3NIa' b 2 0.002880 0.004765 6 0.13 + 0.13 44.7 + 1.3 4.6 + 0.1 0.003 + 0.003

3NIc t-BUMe 3 0.002947 0.006091 0.4 + 0.2 64.6 + 1.5 8.1 + 0.3 0.006 ± 0.00

s-BUMe3NIa 2 0.002899 0.005574 5 80.4 + o.6 11.0 + 0.1 8.3 + 0.3 7.32 + 0.05 a Et3MeNI 2 0.002994 0.004848 8 73.2 + 1.1 1.2 + 0.1 44.6 + 0.9 59 + 4 c Et MeNI 0.003189 0.009674 11 63.0 + 0.7 1.6 + 0.2 25.4 + 0.3 4o + 6 3 3 Et3MeNI 4 0.002879 0.02879 11 80.o + o.8 2.34 + 0.02 15.1 + 0.3 32.8 + 0.5 a Et3MeNI 5 0.002863 0.00242 12 86.7 ± 1.9 1.77 ± 0.05 73.4 ± 1.2 47.0 + 2.3

Yields based on sodium. bSample stood overnight in collection tube before analysis was performed. °fields based on salt. 109

were non-reproducible.

Etperiments 12y. ammonia technique 1.--The results of reactions wherein ammonia technique 1 was used are given in Table 11. Examination of the table will show that reproducible results were obtained when the ammonia was allowed to come to the boiling point before the addition of sodium in each run. Effect of temperature on methane to alkane ratio.--Some reactions of sec-butyltrimethylammonium iodide and of tri-n-butylmethylammonium bromide were carried out at or near the temperature of a dry ice-acetone bath. The data from these reactions is presented in Table 11; the data are so annotated as to indicate the conditions under which the reactions were carried out. These reactions were carried out in sealed systems. The usual apparatus was used, with a three way stopcock intervening between the ammonia tank and the apparatus. When the requisite amount of liquid ammonia had condensed (50 ml.), the three way stopcock was turned so as simultaneously to vent off the ammonia from the tank to the atmosphere and to seal off the system. After about five minutes had passed (to ensure that the solution was at dry ice bath temperature) the sodium was added. The apparatus was then allowed to stand until the sodium blue color discharged. The dry ice bath was then removed, the ammonia tank valve was opened, and the stopcock turned so as to bubble ammonia into the liquid. The procedure from this point was as already described. Some trouble was had with freezing of ammonia (after reaction had ceased) when dry ice-acetone baths were used. This was obviated by use of dry ice-ethanol baths, which gave a temperature

Table 11. Products from Reactions of Tetraalkylammonium Halides

with Sodium in Liquid Ammonia, Technique 1

Salt Run Salt Sodium Reac. Yield Yield Yield Ratio No. moles g. atoms Time, CH4 Alkene Alkene CH4/03412m42 min. a n-Bu3MeNI 1 0.002978 0.004861 2 91.7 + 1.7 1.7 + 0.1 7.0 + 0.3 52 + 3

n-Bu3MeNIa 3 0.002936 0.005078 16 98.2 + 1.4 2.05 + 0.021 0.7 + 0.3 47.8 + 1.5 n-Bu3MeNII) 4 0.002485 0.005222 3 87.0 + 2.0 1.93 + 0.013 0.7 + 0.3 45.1 + 1.1 n-Bu3MeNBra 3 0.002977 0.004835 2 94.7 + 1.8 1.88 + 0.047 8,3 + 0.5 50.4 + 1.6 n-Bu3MeNBra 5 0.002836 0.004952 4 95.5 + 2.4 2.01 + 0.080 2.7 + 0.2 47.7 + 1.8 b n-Bu3 mdler 6 0.0009854 0.004839 85.3 + 3.2 1.76 + 0.057 0.8 + 1.6 48.7 + 2,3 E-Buptiara 7 0.002931 0.001657 2 92.1 + 1.6 1.8o + 0.08 46.0 + 1.9 51.2 + 2.5 a 8 0.001022 0.001396 1 9603 + 1.3 1.73 ± 0.12 15.8 + 2.0 55.6 + 4.3 -n -Bu 3 MeNBr E-BupeNBra,c 9 0.001709 0.001513 136 58.8 + 0.8 0.251 + 0.10 16.0 + 1.6 235 + 117

n-Bu3menraY c 10 0.002984 0.00477 79 40.1 + 0.8 0.162 + 0.037 28.1 + 1.1 247 + 57

n-Bu2Me2VBra 1 0.003203 0.004996 7 90.2 + 1.6 0.812 + 0.038 0.6 + 0.2 111 + 5.6

n-Bu2Me2EBra 2 0.002584 0.005009 6 72.4 + 1.8 0.636 + 00068 0.4 + 0.2 114 + 9.7

n-BuMe3NI8' 6 0.003065 0.004743 4 98.0 + 1.6 0.272 + 0.032 2.4 ± 0.4 360 ± 43

n-Bume3Nia 7 0.002886 0.005374 7 94.5 + 1,9 0.304 ± 0.028 1.0 + 0.3 310 + 29 a p-BuMe3NBr 1 0.003035 0.004887 9 90.4 ± 0.6 0.33 + 0.02 o.8 4 0.3 277 ± 29 Table 11 (continued)

Salt Run Salt Sodium Reac. Yield Yield Yield Ratio No. moles g.-atams Time) CH4 Aikane Alkene CH4/C 0'2n71-2 • R-BuMe3NBra, d 2 0.003134 0.005552 22 87. 5 + 1.4 0.378 + 0.029 0.5 + 0.3 232 + 18 n.BuMe3NCla 6 0.002698 0.005135 13 98.0 + 2.3 0.308 + 0.034 0.7 + 0.3 318 + 36

21-BuMe3Nnla 7 0.003089 0.004757 5 96.3 + 1.9 0.336 + 0.033 1.4 + 0.3 286 + 28

11-BuMe3NIa 1 0.003034 0.005913 3 67.1 + 1.1 10.0 + 0.27e 4.1 + 0.3 6.73 + 0.13 e

1-BuMe3NIa 3 0.003011 0.004839 10 59.1 + 1.5 8.47 + 0.22 8.7 + 0.3 6.99 + 0.26

24BuMe3NIa,f 4 0.002140 0.004174 115 17.8 + 0.7 1.66 + 0.07 31.1 + 2.5 10.7 + 0.6

2-BuMe3Nia,f 5 0.002866 0.004665 260 17.1 + 0.38 1.43 + 0.046 34.5 + 1.1 12,0 + 0.47

L-BuMe3NIb 1 0.002944 0.004970 3 0.00 + 0.18 76.2 + 2.7 11.7 + 0.5 0 + 0.002

L-Buble3lab 4 0.0005445 0.004713 OV71. 0.00 + 0.48 75.0+ 1.3 2.4 + 1.6 0.00o + 0.006

1-BuMe3NI- a 5 0.003083 0.005943 4 o.359 + 0,111 72.4 + 1.6 1,8 + 005 0.0047 + 0.00115

L-BuMegIa 6 0.002833 0,005130 1 0.302 + 0.061 88.o + 2.0 8.2 + 0.6 0.00343 + 0.00069 a n-Pr3MaNI 1 0.002859 0.005113 4 94.3 + 2.4 4.51 + 0.070 2.2 + 0.3 20.9 + 0.6

a 2 0.002900 0.004965 92.5 + 0.15 4.70 + 0.15 2.6 n-Pr3, MeNI 3 + o.6 19.7 + 0,8 a 1 0.002898 0.004835 n-PrMe 3NI 5 94.8 + 2.3 0.570 + 0.060 1.2 + 0.4 166 ± 18 a n-PrMe3NI 2 0.002936 0.004843 6 86.6 ± 1.4 0.488 + 0.044 1.9 + 0.3 177 + 16 i-PrMe 1 0.002738 0.004883 2,1 3 Nib 5 75.6 + 3.56 ± 0.062 18.8 + 0.3 21.2 + 0.7

112

1-1 t---- C-- co 0 N H -1- . H 0 0 H CV N N H H 0 0 +I +1 +1 CO +1 +1 +I +I +1 +I U>\ N. CY-3 N -I-1 C.- C--- 0. -I- C": 0 +1 00 00 0 a Cvl N H H H 0 \ N C.- CO If \ CO N N N -I- --I' cn ...* in CO N cr) C--- -1-

-1- N CO in -1- cn N. -1- CO • 0000 0 O 0 00 • 000000000000 A +1 +1 +1 +1 +1 +1 +1 +1 +1 +I +1 +1 W r-I O\ es C--- N 9 C-- .4 000 COO 9 9 Ha Lr, 0 COCOO\ n n n -1- ON O\ oN U' \.0 H H CI, in in N N in N CV N

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rtg

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En 47) 0 0 0 0° 6 c; c; ic; O' o 0 0 lt.

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g c; NHN 1-1\0C.-HNHNHN bas

14 ds

to l Yie

,00 b in '13H U O °pH H XCD g CO CO Ze M' A in -HI 4MMMM Table 11 (continued) eValue based on 6.840 micron calibration for butane, optical density 0.246.

(Reaction run at temperature of dry ice-ethanol bath, -72 ° . gSame reaction products lost in manipulations. hSodium added four minutes before liquid ammonia reached its boiling point. 114

slightly above that of the freezing point of ammonia.

Effect of varying concentrations on methane to alkane ratio.--An examine:- tion of Table 11 will reveal that Runs 6, 7, and 8 of tributylmethyl-

ammonium bromide were run with concentrations varying from those usually

employed (0.003 mole sale, 0.005 mole sodium). This was done to test

an assertion of Blanchard, namely, that the methane to butane ratio will

vary with concentration of salt employed. 4 Note that both sodium and

salt concentrations were varied.

Reactions of tetra-n-alkylammonium halides with sodium in liquid

ammonia.--Tetra-n-alkylammonium halides bearing as substituents in each

case only methyl, ethyl, n-propyl, and n-butyl groups were reacted with

sodium in liquid ammonia at the boiling point not only to obtain general

information about these reactions but also to compare roughly the rates

of reaction; the latter goal was not satisfactorily achieved. Results of these experiments are given in Table 12, Run 1 of tetraethylammonium bromide was not analyzed quantitatively as the amount of salt taken was unknown.

Solubility of tetraalkylammonium halides in liquid ammonia.--All but a

few of the quaternary ammonium halides used were soluble in liquid

ammonia at its boiling point and at the concentrations normally employed

(0.06 mole/liter). Very crudely estimated solubilities (from visual

observations of the apparent fraction of salt which dissolved) of those

salts which were not completely soluble at the concentrations employed

are: tetra-n-propylammonium bromide, 0.05 mole per liter; tetraethyl-

ammonium bromide;, 0.2 mole per liter; tetramethylammonium bromide, 115

Table 12 . Products from React ions of Symmetric ally Substituted Quaternary Ammonium Halides with Sodium in Liquid Ammonia

Salt Run Salt Sodium Ileac. Yield Yield No. moles g.-atoms Time, Alkane Alkene min. % E-Bu4NBra 1 0.002986 0.005865 12 79.2 2.9 n-Bu4NBrb 2 0.01002 0.004417 11 89.5 + 1.0 40.3 + 1.0 n-Bu4yaxb 3 0.009977 0.004278 7 87.4 + 0.41 42.7 + 1.1 n-Pr4NBrb 1 0.01008 0.004287 5 76.3 + 1.4 38.5 + 0.6 n-Pr4NBrb 2 0.009454 0.004496 4 83.7 + 1.0 36.4 + 1.8 n4nra 2 0.002935 0.0062 57.5 36.2 Btoera 3 0.01571 0.004261 33 81.5 + 1.6 76.0 + 0.8 tt4NEra 4 0.01093 0.004452 35 88.6 + 1.2 84.8 + 0.7 me4wBra 1 0.0103 0.0517 -- 7 ..__

Mega 2 0.001625 0.0043 5 ••• b Me4N2x 3 0.001014 0.001005 5o 36.5 ___ me4NBrb 4 0.004937 0.00614 120 90.6 SO meoBrb,c 5 0.01004 0.004304 7o 94.4 + 1.5 ••• • Oft

aYields based on salt taken.

bYields based on sodium taken. cNo ethane detectable by infrared analysis. Maximum yield ethylene, 0.4 + 0.4 per cent by chemical absorption. 116

"insoluble"; t-butyltrimethylmxmonium iodide, 0.002 mole per liter. In

all cases, these solubility data were obtained in connection with the

experiments run in liquid ammonia and no attempt was made to obtain more nearly quantitative solubility data. These solubility estimates have been made since they are required for reasoning later in this thesis; they may, however, be in error by a factor of ten or more.

Basis of reporting yields.' Yields were reported on the basis of salt taken or sodium taken, depending on which was present in lesser amount according to the equation

li4NX + 2Na + NH3 RH + R3N + NaX + NaNH2 .

When yields were reported on the basis of sodium, alkene yields were reported as though two moles of sodium were required to produce one mole of alkene; this was done in order to report alkene and alkane yields on the same basis for quantitative comparisons. Actually, the alkene probably arises largely from the action of amide ions

R CH2CH2N(CH3 ) 3X + = CH2 + (CH3)3N 4-I - + NH3 which may either be produced as above or catalytically, i.e.,

2NH3 2/48,--4-2Na+ + 2NH2- H2

This explains why yields based on sodium often exceed 100 per cent. In some cases even when alkene yields as given are divided by two, the total yield is in excess of 100 per cent. This must be due to the sodamide or other basic ions formed in the reductive cleavage reaction, which may in 1 17

turn give rise to a Hofmann-type elimination reaction on the "excess" salt.

Nature of products.--The unsaturated gas produced was assumed to correspond to the alkyl group(s) present in the compound studied since sufficient gas was not generated in a run to determine this by infrared spectra in addition to the other analyses. The nature of the saturated hydrocarbons in each case was shown by infrared spectra to correspond to the substituents in the compound studied, thus to be methane and n- butane when trimetbyl-n-butylammonium ion was cleaved. 118

CHAPTER VIII

REACTIONS OF OMMA-CHLOROALKYLTRIMETBYLAMMONIUM HALIDES WITH SODIUM

The Reaction of 5-Chloroamyltrimethylammoniwn Chloride with Sodium in Dioxane

Run 1

Materials.--0.0916 mole salt

0.517 g.-atom sodium

250 ml. dioxane

Apparatus.- -As described in apparatus section for dioxane runs (Technique

2).

Procedure.--The salt was added by increments over a period of 41 minutes.

The reaction was considered complete an hour and 28 minutes after the initial salt addition. The total volume of gas evolved was 2075 ml.

After the distillation of solvent had been carried out as usual, the system was swept with three liters of nitrogen.

The distillation receiver was removed and an aliquot of its contents titrated with standard hydrochloric acid. The distillate was then transferred to a 500 ml. three-necked flask attached by one of its necks to a heated three-feet long distilling column packed with glass helices.

Nitrogen could be led in through one of the necks of the flask; the third neck was stoppered. Water for the reflux condenser at the top 119

of the column was heated to 35 ° by running it through a copper coil heated by the flame of a Tirrell burner. Thus, by allowing the dioxane distillate to reflux for 45 minutes, some of the less volatile gas was recovered from the dioxane. To prevent the passage of amines into the gas collection bottle, two gas scrubbers containing ca. 001 N hydrochloric acid were used between the gas takeoff at the top of the column and the gas collection bottle. After turning off the pot heat, nitrogen was swept through the system to bring the total volume in. the gas collection bottle to 2600 ml. The contents of the sodium reaction flask were treated with ethanol to destroy sodium, and the flask sealed. After 12 days 50 ml, of water was added; the mixture was then extracted with 150 mlo of ether, in three portions of about 50 ml, each. The ether layer was separated and distilled. The distillate was titrated with standard hydrochloric acid to a methyl red end point. Black material appeared when a mixture of the dioxane distillate and the contents of the scrubbers from the sodium reaction (an amine hydrochloride solution) were evaporated to dryness in an attempt to apply a Hofmann exhaustive methylation procedure. Methiodides were, however, obtained from the residue and their average equivalent weight was determined to be 223 by means of an absorption indicator titration.

No pyrolysis was performed. The principle gaseous products were identified as pentene-1 and methane by means of infrared spectra. Small amounts of ethylene and acetylene were evidenced by their strongest absorption bands at 10.54 120

and 13.71 microns respectively. The spectrum of the gas obtained by refluxing the dioxane distillate apparently indicated exclusively pentene-1.

Quantitative estimations of the hydrocarbon yields were made by Orsat and by infrared techniques. Fifteen combustion analyses were attempted for methane, only two of which gave meaningful results. Con- siderable trouble was had with carbonization in the others. Other infrared and classical Orsat analyses were performed as described in Chapter N. Yields were: total amine, 74.1 per cent, 25.8 per cent from the scrubbers, 35.5 per cent from dioxane distillate, and 12.8 per cent from distillation of the flask residue; pentene-1, 17,3 per cent, 11.7 per cent from gas collected during the reaction and 5.6 per cent recovered from the dioxane distillate; methane, 45 per cent by combustion analysis or 42 per cent by light absorption analysis in the infrared.

Run 2 Materials.--0.0778 mole salt

0.512 g.-atom sodium

250 ml, dioxane Apparatus.--Same as in Run 1, except the gas scrubbers were immersed in a bath maintained at about 50° .

Procedure.--The salt was added in four increments over a half-hour period. The reaction was considered complete 40 minutes after stirring had been started. The stirrer was stopped and the dioxane kept refluxing for an hour and a half. The cooler parts of the system were heated with an 121

infrared heat lamp during the last half hour of refluxing. The flask contents were distilled nearly to dryness and, after 125 ml. more dioxane was added, the flask was again distilled nearly to dryness. The dioxane distillate was subjected to additional treatment as in Run 1 for removal of less volatile hydrocarbon. The gas so separated (two liters of nitrogen employed for sweeping) was shown to contain unsaturates by absorption in mercuric sulfate solution.

The excess sodium in the reaction flask residue was destroyed by addition of ethanol; 120 ml° of water was then added, followed by 100 ml, of ether. The two resulting layers were separated and the aqueous layer extracted twice more with 50 ml, portions of ether. The organic layer was distilled into excess standard hydrochloric acid to determine the amines present.

The aqueous layer from the above extraction was acidified with hydrochloric acid and evaporated to dryness. The material thus obtained (mostly sodium chloride) was placed in a Soxhlet extraction thimble and extracted with dry t-butyl alcohol a total of 27 hours. The pot liquor turned brown during the extraction° The t-butyl alcohol solution was mixed with 125 ml, of dry ether and stored in the refrigerator in a glass stoppered flask. After nine days, only a small amount of solid brown material had come out of the solution; this was taken as evidence that no appreciable amount of unreacted salt remained after the sodium reaction.

Qualitative analysis of the products of Run 2 gave the same results as for Run 1. The yields of products were unsaturates, 1209 122

per cent, 11,6 per cent from the gas collected during the reaction, and

1.3 per cent from that recovered from the dioxane distillate; methane,

35 per cent (all collected during the sodium reaction); amines, 49.8 per cent, 18.8 per cent from the dioxane distillate, 21,2 per cent from the gas scrubbers, and 9.8 per cent from distillation of the ether extract of the contents of the reaction flask.

A Hofmann methylation and pyrolysis procedure was attempted on the combined amine hydrochlorides. The average equivalent weight of the methiodides was determined to be about 249. pyrolysis of the hydroxides derived from these methiodides was carried out, but the pot broke during the heating, with resultant loss of the hydrocarbons generated.

Run 3 Materials.--0.0737 mole salt k

0.492 g.-atom sodium

250 ml. dioxane

Apparatus.--As for Run 2,

Procedure.--Technique 1 was used. The stirrer was run at 40 to 80 volts.

Perhaps one-third of the reaction mixture was carried over into the distillation receiver due to inadequate control of the stirring rate.

Little sodium was carried over. During the reaction and thereafter the distillation receiver was heated by means of an infrared lamp. The reaction mixture was deep violet. The reaction was considered complete 18 minutes after starting the stirrer. The system was kept under reflux

k99.2 per cent pure, no more than 0.8 per cent bis salt by ionic chlorine analysis. 123

for an hour while a slow stream of nitrogen swept through it The

system was then swept with about seven liters of nitrogen. Throughout the procedure the brine tub was kept heated to about 48° by means of an immersed steam coil.

By means of optical density measurements at 30455 microns, evidence was obtained for the presence of a saturated hydrocarbon other than

methane among the reaction products.

The flask contents (which included unreacted sodium) remaining

after the reaction were transferred with dioxane washings to a liter

flask arranged as part of a simple vacuum distillation assembly. A steam bath was used for heating. The 500 ml, receiver was surrounded by ice.

The flask was taken to dryness in 23 minutes at 29-47 ° and 26-61 mm.

One hundred twenty-five milliliters of dioxane was added and the pot

again taken to dryness in 45 minutes at 34510 and 4798 mm. The distillate was combined with 0.08627 equivalents of hydrochloric acid and the dioxane distillate from the sodium reaction and made up to one liter. Aliquots were withdrawn such that the amine yield could be determined (37.9 per cent non-volatile amine). The amine hydrochloride solution was transferred to a two liter flask and concentrated nearly to dryness under the vacuum of a water aspirator. Nitrogen was admitted slowly to the apparatus during this procedure to insure the exclusion of air; the receiver was surrounded by ice. The residue was taken up with a little water and transferred to a 500 ml, flask s together with washings of the distillation flask- The flask was surrounded by ice and 200 ml, of dry ether introduced. Excess solid potassium hydroxide was added 124

and the ether decanted to a fresh flask. The aqueous phase was shaken

with three more portions (50 ml.) of ether and the ether washings were

decanted into the main portion. Five milliliters (0.083 mole) of methyl

iodide was added. After 29 hours, the methiodides were filtered and

found to amount to 5080 g. (88 per cent yield calculated as amyltrimethyl-

ammonium iodide based on equivalents of amine taken). Etcess silver

oxide was prepared from aqueous solutions of silver nitrate (17 g.) and

potassium hydroxide (6 g.). The silver oxide, following filtration and two water washings, was added to an aqueous solution of the meth-

iodides and the resulting mixture shaken for three hours on the shaking machine; after storage overnight, the mixture was filtered into a

distillation apparatus. Two drops of the filtrate gave no precipitate with acidified silver nitrate solution. The precipitate was washed twice with water and the washings added to the distilling flask. Dis- tillation was carried to dryness and the pot heated to 243°. A slow

stream of nitrogen was passed through the apparatus during this time.

Scrubbers containing 0.06289 equivalent of BC1 diluted to about 500 ml,

intervened between the pyrolysis distillation apparatus and the gas collection bottle. The scrubbers and the brine were heated as previously to 35° or higher. The total volume of gas collected, including nitrogen, was eight liters. A qualitative infrared spectrum confirmed the presence of pentene-1 and trans-piperylene in the gases collected.

This gas was analyzed for total unsaturates in the usual way, indicating

a 46.8 per cent yield of unsaturated hydrocarbons based on methiodides taken. The yield of amines was 70 per cent. The relative amounts of 125

pentene-1 and trans-piperylene were determined by applying the method of

Tropsch and Mattox to analyze for piperylene. ft This method consisted

of bubbling the gas to be analyzed through a small amount of molten

maleic anhydride at 100 ° and measuring the contraction. A flask of water

heated to boiling served to keep the maleic anhydride at 100 ° . In this

way the gas samples were found to contain an average of 0.77 per cent trans-piperylene (molten maleic anhydride does not react with cis- piperylene62 ); by calculating an extinction coefficient from an API

spectrum 52at 6.25 microns and using the optical density from the qualitative spectrum taken, the concentration of trans-piperylene in the

samples was calculated to be 0.81 per cent by volume, in good agreement with the chemical data. The samples contained 3.35 per cent by volume total unsaturates. A 70 per cent yield of amines from methiodides was obtained.

The volatile amine hydrochlorides (from scrubbers used in sodium reaction) were similarly treated. A 71.5 per cent yield of methiodides was obtained from the hydrochlorides; nine per cent yield is estimated to have been lost mechanically. A 100 ml. solution of the methiodides was shaken for two hours with excess moist silver oxide prepared from

35 g, of silver nitrate and 6.7 g. of potassium hydroxide and washed once. The next day the material was filtered such that the filtrate was collected in the pyrolysis apparatus. Tests of a few drops of the

61H. Tropsch and W. J. Mattox„ Ind. En go Chem., Anal. Ed., 6 104 (1930.

62R. F. Robey, Co E. Morrell, and H. K. Wiese, J. Am. Chem. Soc., 627 (1941). X26

filtrate with acidified silver nitrate solution showed that no halide ion was present. The maximum temperature during the pyrolysis was 230 ° . The amine yield from the pyrolysis was 70 per cent (based on methiodides).

The infrared spectrum of the products showed no bands, except possibly for ethylene (no more than 0.3 mm. partial pressure).

From the preceding procedures, yields of the various products were estimated. In the usual way, hydrocarbon yields were determined to be:

Methane, 39.6+ 1.1 per cent;

Higher alkane, 0.31 per cent reported as n-pentane;

Unsaturated hydrocarbons, 29.7 ± 1.1 per cent, principally pentene-'l, with possibly some ethylene and acetylene.

Yields of individual amines were estimated on the basis that the exhaustive methylation procedures and Hofmann degradations should have given the theoretical yields throughout. It was, therefore, assumed that the amines were present in the same ratio as the products obtained from the Hofmann degradation. The yields then were as follows:

Total amine, 78.5 per cent;

Volatile amine, 40.6 per cent, including 002 to 0.3 per cent yield of ethyldimethylamine and the remainder trimethylamine;

Non volatile amine, 37.9 per cent, including an 8.8 per cent yield of pent enyldimethylamine and the remainder amyldimethylamine.

After this data was collected cyclopentane was calibrated for analysis at 3.455 microns. On the basis of this calibration curve there could have been no more than 0.34 per cent yield of cyclopentane, if present at all. The material absorbing at 3.455 microns in the infrared 127

could have been and probably was n-pentane.

The Reaction of 2-Chloroethyltrimethylammonium Chloride with Sodium and with Zinc Dust

The Reagtion of 2-Chloroethylammonium Chloride with Zinc Dust in Aqueous Rthanol-L

Materials.--0.0886 mole salt

0.329 g.-atom zinc dust

11.5 g. sodium iodide

2.5 g. sodium carbonate

Apparatus.--As described for dioxane runs.

Procedure.--Technique 2 as used in dioxane runs was employed. The zinc

dust was activated by washing it with 0.1 N hydrochloric acid followed

by washing with water and 95 per cent ethanol. The zinc dust, sodium

carbonate, and sodium iodide were then mixed with 200 ml, of 75 per

cent ethanol and placed in the Morton flask. The ammonium salt was

dissolved in 70 ml. of 75 per cent ethanol and placed in the dropping

funnel at the top of the column. After satisfactory refluxing and

stirring were obtained, the ammonium salt solution was added over a

period of two hours (nine additions). The reaction was considered com-

plete after three hours and the distillation procedure was carried out

as usual. Analyses were carried out as previously described. Yield

data to this point (ethylene and amine yields) are given for Mills 1, 2

and 3 in Table 13.

The amine hydrochlorides from the bubblers (Run 2) were subjected to methylation and to Hofmann degradation; no unsaturated or other gas

1Data given for Run 2. 128

Table 13. Results of Reaction of 2-Chloroethylammonium

Chloride with Zinc Dust in Aqueous Ethanol

Run Salt, Zinc Nala Na2C0; Yield Yield CO2, No. moles g.-atoms grams gram Amine Ethylene moles

1 0.112 0.358 12.0 2.8 38.7 39.4 0.0212

2 0.0886 0.329 11.5 2.5 52.0 60.4 0.0364

3c 0.109 0.306 110 none 15.1 40.7 none

aC. P. grade.

bC. P. anhydrous grade.

0-Five hours stirring time. 129

was obtained indicating that probably no amines other than trimethylamine had been obtained from the reaction. The following procedure was carried out for Run 2 only. The flask residue from the zinc reaction was filtered and washed five times with water; the filtrate and washings were made up to one liter and aliquots withdrawn. The samples were neutralized with dilute nitric acid and titrated with silver nitrate to a dichlorofluorescein end point. The ammonium salt was thus shown to have undergone reaction to the extent of 81.9 per cent, an appropriate correction having been made for the

iodide ion present.

The contents of the volumetric flask were nen evaporated to dryness; dilute hydrochloric acid was added until the material was slightly

acid to methyl red, and the solution again evaporated to dryness. The

apparently dry material was stored overnight over phosphorus pentoxide in a Soxhlet extraction thimble, dried in the vacuum oven at 73° for eight hours, and stored over phosphorus pentoxide for two weeks. The material was treated with absolute ethanol for a total of 21 hours in a Soxhlet extractor protected from moisture by a Drierite tube. Filtra- tion of the cooled pot liquor followed by washing of the precipitate with dry ether yielded 3.52 g. of fine needle-like crystals admixed with a small amount of brown powdery material (25.8 per cent yield calculated as vinyltrimethylammonium chloride). The crystals melted on ignition, blackened, and left a char residue which disappeared on further ignition. A rapid melting point was taken the material began to decompose at 170°, and finally melted at 192° (m. p. 2-chloroethyltrimethylammonium 130

chloride, 240-40; 63 m- po vinyltrimetbylammonium chloride, 193 j+0 64).

A dilute water solution of the material gave a precipitate with silver nitrate solution. The material did not seem to decolorize bromine water, but did seem to decolorize a very dilute permanganate solution.

The remaining material was shaken with freshly prepared moist

silver oxide, filtered into a distillation apparatus, and pyrolyzed as described previously. The infrared spectrum of the collected gaseous product from 2 to 14 microns showed it to be acetylene. No ethylene was detectable. Based on the original 2-chloroethyltrimethylammonium chloride, Orsat anAlysis gave a yield of acetylene of eight per cent

(mercuric sulfate absorption). The yield from the assumed vinyltrimethylammonium chloride was 2205 per cent (0.0065 mole acetylene were evolved). If, however, the salt was assumed to be the iodide, the yield of acetylene therefrom would be 40 per cent. Amines evolved amounted to 000117 equivalent: a 13,2 per cent overall yield based on

2-chloroethyltrimethylammonium chloride; a 4006 per cent from the unknown salt as vinyltrimethylammonium chloride; or a 7105 per cent from the unknown salt as vinyltrimethylammonium iodide.

The Reaction of 2-Chloroethyltrimethylammonium Chloride with Sodium in Dioxane-t-Amyl Alcohol

Materials.--0.117 mole salt

140 ml, dioxane

63T. Harada, Bull. Chem. Soc. Japan, 6, 25 (1931).

64C. Gardner, V. Kerrigan, J. D. Rose, and B. C. L. Weedon, J. Chem. Soc., 789 (1949). 131

110 ml. t-amyl alcohol 0.563 g.-atom sodium

Procedure.--Dioxane technique I was used. The products were ethylene, acetylene, and a product assumed to be trimethylamine. Orsat analyses were carried out in which ammoniacal silver chloride was used for deter- 6, 66 mination of the acetylene. Mercuric iodide-potassium iodide reagent proved unsatisfactory for the analyses. The yields (all based on salt) found were as follows: acetylene, 47.8 per cent; ethylene, 47.4 per cent; amines, 86.3 per cent. The amine yield is undoubtedly lower than the hydrocarbon yield due to the system's having been swept with nitrogen before the distillation procedure only.

The Reaction of 2-Chloroettryltrimethylammonium Chloride with Sodium-t- Amyl Oxide Materials.--0.108 mole salt 250 ml. t-anrl alcohol

0.464 g.-atom sodium

Apparatus.- -As in other dioxane runs.

Procedure.--The solvent and sodiumfon .137). were added to the reaction flask and the salt addition flask. was wired in place. The system was brought to reflux and stirring begun, a vigorous evolution of gas began and some distillation of solvent took place. A faint "hydrocarbon" odor was observed at the tube where the evolved gases were being discharged

65S. A. Tucker and H. R. Moody, J. Am-Chem. Soc., 23, 671 (1901). 66 F. Bayer, Gassnely, Ferdinand Enke, Stuttgart, 1938, p. 42. 132

to the atmosphere. m The sodium dissolved. completely in about an hour

and 20 minutes after which the stirrer was stopped. The system was

swept with nitrogen; the sweeping was stopped, the gas collection bottle

connected, and the salt introduced into the reaction flask. Gas evolution began before the stirrer was started and yielded a liter of gas in

five minutes. Stirring was then carried out for 20 minutes to yield

1500 ml, of additional gas. An attempted adjustment to the stirrer at this point gave rise to an obvious loss of gas from the system; the re-

action was considered complete at this point and the rest of the procedure carried out as for Dioxane Technique 1. Five liters of nitrogen was used

for sweeping the system. The gas evolved was shown by its infrared spectrum to be acetylene only. Orsat analysis indicated a yield of

80.6 per cent. The amine yield was 84.4 per cent.

The Reaction of Chloromethyltrimethylaamonium Bromide with Sodium

The Reaction of Chloromethyltrimetbylammonium Bromide with Sodium in Dioxane

Materials.--Materials as used in the nine runs of this salt are given in Table 14.

Apparatus.--As for other dioxane runs,

Procedure.--Dioxane Technique 2 was used for Runs I through 4 and for Run

6. Dioxane Technique 1 was used for the remaining runs.

In Rums 6 and 7, after the dioxane distillation had been completed

mcf. Reaction of t-Amyl Alcohol with Sodium, Chapter VI. Table 14. The Reaction of Chloromethyltrimethylammonium Bromide

with Sodium in Dioxane

Run Salt Sodium Rene. Tar, Sweep No. moles g.-atoms Methane Ethylene Total C2H5N (CH )2 CH2;=CHF CH3),,,, Time g. Gas, Amine max, mid. c max, min. min. 1.

1 0.108 0.545 3.5d 15.8 14.4b ___ 218 1 3 2 0.107 0.656 6.2±o.6d 40±4 45.0 ...._ ___ ...._ 228 0.7 2.5 3 0.113 0.580 12.8±1.id 36.441.0 44.71, ______...._ ___ 130 --- 2 4 0.1338 0.537 ___ 13 62.7 8.9 4.2 0.4 0.2 105 0.7 2.5

5 0.101 0.501 10.3 25.6 32.4 trace trace 108 o.6 9 6e 0.09236 0.507 12.2 37.5 76.2 26.5 19.5 trace trace 182 2.8 3 7e 0.1005 0.510 11.0 29.6 83,7 43 0 1 28.8 trace trace 98 0.6 10 8 0.0996 0.503 23.51-004 13 06 68.7 1504 7.8 trace trace 117 ___ 4 9a 0.0754 0.602 9.1 43 66.1 17.6 9 0 8 0.9 0.5 80 --- 3

aRun 9 of chloromethyltrimethylammonium chloride, b"Volatile amine" only (does not include amine in dioxane distillate). clrield given as twice mole per cent. dBased on Orsat combustion analysis. aSodium reaction followed by treatment with t-amyl alcohol; yields given are the totrl yields obtained. 134

in the usual manner and the system swept with nitrogen, the rubber tube leading from the gas takeoff at the distillation receiver was connected to a fresh train of HCl scrubbers, the final outlet of which led to a fresh gas collection bottle. t-Amyl alcohol (110 ml.) was then added to the reaction flask and the stirrer again started. When the gas evolution had stopped, the system was swept with nitrogen and the gas collection bottle sealed. In Run 6, the t=amyl alcohol treatment gave an amine yield of 7,9 per cent, an ethylene yield of 1.8 per cent, and a methane yield of 0.65 per cent; in Run 7, an amine yield of 11.2 per cent, an ethylene yield of 1.1 per cent, and a methane yield of

0.98 per cent. All yields were based upon the amount of salt used.

The combined scrubbers' contents and dioxane distillate were subjected to a Hofmann exhaustive methylation and pyrolysis procedure in Runs 4 through 9. The minimum yield of ethyldimethylamine given in

Table 13 is the moles of ethylene found in the pyrolysis divided by the moles of salt taken times 100 (corrected for any aliquots withdrawn). The maximum yield is the ratio of the moles of ethylene from the pyrolysis to the total yield of amines from the pyrolysis times the yield of amines from the sodium reaction. The vinyldimethylamine yields are calculated analogously from acetylene evolved in the pyrolyses. If the figures so calculated disagreed markedly with the required stoichiometry of the reaction, the maximum ethyldimethylamine yield was given as the difference between the total amine yield and the combined ethylene and methane yields from the sodium reaction.

In Run 5, the material remaining in the Morton flask after the 135

reaction was filtered from the sodium (suction) and the filtrate shaken with 100 ml, of water and 100 ml, of ether. The ether layer was separated

and the aqueous phase extracted with three more portions of ether.

Throughout the treatment the aqueous layer contained a dark, dirty brown

suspension. The evaporated ether extract yielded 0.6 g, of a waxy brown

solid, listed as "tar" in Table 13, The flask residues from Runs 1, 2,

4, 6 and 7 were treated similarly, except excess sodium, if present, was destroyed with ethanol and the filtration consequently omitted. The ethylene and methane from each run were identified by means of their infrared spectra.

The Reaction of Chloromethyltrimethylammonium Bromide with Sodium in Liquid Ammonia, Run 1

Materials.--0.008758 mole salt

0.0248 g.-atom sodium

Apparatus.--Liquid ammonia apparatus described in Chapter IV. A rubber stopple replaced retort n. The reaction tube was jointed so that the bottom half could be removed.

Procedure.--Liquid ammonia Technique 2 was used; the salt was added in small increments. Each addition gave rise to an immediate reaction, as evidenced by the ebullition observed. Thirty-three minutes after the first addition of salt, the sodium blue color had discharged. Some of the sodium had been deposited on the upper portion of the reaction tube. Only about

20 ml. of the original 50 ml, of liquid ammonia remained at this point.

One milliliter of absolute ethanol was injected (in three portions) through the rubber stopple, in order to destroy sodamide. The liquid 136

ammonia was evaporated and the gas analyzed in the usual manner. The white powder remaining in the apparatus was transferred with the aid of some water to an Erlenmeyer flask. The resulting solution was made Just neutral to methyl red with 60 ml. of 0.2 N hydrochloric acid. The solution was evaporated to dryness and the resulting residue taken up in 30 ml. of boiling absolute ethanol, shaken, and filtered. The filtrate was evaporated to a small volume whereupon crystals precipitated. Dry ether was added and the crystals were separated by filtration. A picrate was prepared from the material as described in

Chapter II. The melting point was 322.5-324° (uncorrected); Blanchard gives 325-326° for the melting point of tetramethylammonium picrate, but only 253-254° for the melting point of chloromethyltrimethylammonium picrate. 33 A mixed melting point with authentic tetramethylammonium picrate gave 322.5-323.5° (uncorrected). The weight of picrate isolated corresponded to 0.3 per cent yield of tetramethylammonium ion; it should be pointed out, however, that no effort was directed toward obtaining quantitative results in the above described treatment of the solid reaction residue, and much more tetramethylammonium salt may have been present.

The ethylene yield was 3.7 per cent (given as twice mole per cent) and the methane yield was 32.9 per cent. All yields for this reaction were based on salt taken.

The Reaction of Chloromethyltrimethylammonium Bromide with Sodium in Liquid Ammonia, Run 2

Materials.--0.003323 mole salt 0.00673 g.-atom sodium 137

Apparatus.--As in Run 1.

Procedure.--Ammonia Technique 2 was used; all the salt was added at once at the temperature of the dry ice bath. The dry ice bath was removed, and within a minute or two there was a light brown region of solution at the bottom of the reaction tube; the solution above this was dark blue.

At the fifteenth minute, the contents of the tube were seen to be an olive-khaki in color. Absolute ethanol (0.5 ml,) was then introduced through the stopple. The liquid ammonia was evaporated and the gaseous products analyzed in the usual manner. The dry residue in the reaction tube amounted to 0.63 g. of light brown powder. Two milliliters of 6 N hydrochloric acid was added to the powder on a watch glass; this treatment resulted in an ebullition and a darker brown color. No further treatment was attempted due to loss of the material through accident.

The yield of ethylene was 8.6 per cent and of methane 5.1 per cent; calculations of the yields were made as for Run 1.

The Reaction of Chloramethyltrimethylammonium Bromide with Sodium in Liquid Ammonia, Run 3

Materials,--0.003689 mole salt

0.007139 g.-atom sodium

Apparatus.--As in Run 2.

Procedure.--Liquid ammonia Technique 2 was used. The salt was added well below the boiling point of the liquid ammonia. One minute after the addition, white streaks could be seen extending up into the blue solution. One minute and 40 seconds after the addition, the bottom four- fifths of the solution was a light brownish yellow; the top one-fifth 138

maintained the characteristic blue color. Four minutes after the addition,

the ammonia came to boiling. Eight minutes after the addition, the re-

action mixture was blue-green. Absolute ethanol (0.5 cc.) was injected through the rubber stopple at this point. There was 16 ml. of gas in the collection tube before the ethanol was added. This would amount to a maximum 17.3 per cent (mole for mole) yield of gas based on salt taken. The gas was transferred to an Orsat burette (diluted with air) and bubbled through RC1 to remove amines. The gas was then placed over mercury in a combustion pipette, which was attached to the gas handling

apparatus by means of a Drierite drying tube. The system was evacuated back to the stopcock of the combustion pipette, and the gas admitted to

the gas cell. The qualitative infrared spectrum of the gas indicated

that it was ethylene and methane only. The residue in the apparatus after the reaction amounted to 0.90

g. of light brown powder. The maximum amount of sodium ethoxide which

could have been present is 0.25 g., as half the sodium has to react to

form halide, according to the equation

2Na + C1C1I2N(CH3)3Br•2Na - + + CH2N(CH3 ) 3Br

If an equal distribution between sodium chloride and sodium bromide is assumed in the dry salt, 0.29 g. can be mixed sodium halides.

Therefore, 0.36 g. may remain as tetramethylammonium halide. If an

equal distribution between bromide and chloride is assumed, this would amount to 0.0028 mole or a 75 per cent yield. The discussion in this paragraph is, of course, only a conjecture but put forth because of the

qualitative identification of tetramethylammonium ion in Run 1. 139

CHAPTER DC

TESTS OF STABILITY OF PRODUCTS AND SOLVENT UNDER

REACTION CONDITIONS

Introduction

In view of the possibility that certain of the reaction products evolved in the reactions studied might, through unprecedented reactions, give rise to gaseous products, several unlikely reactions were attempted. Sodium in liquid ammonia is said not to reduce isolated double bonds. 67 However, only a trace of butane-1 need be reduced to n-butane to alter the methane to butane ratios in some of the reactions studied in liquid ammonia. Furthermore, Greenfield and coworkers have shown that hexene-1 can be reduced to n-hexane in 41 per cent yield by reaction with sodium and methanol in liquid ammonia. 68 Consequently, the behaviors of butane-1 and of isobutene with sodium in liquid ammonia were investigated.

Gilman and Dietrich have been able to cleave triphenylamine with lithium in tetrahydrofuran (three hours reaction time) to obtain a nine per cent yield of diphenylamine. 69 An examination of the literature

67G. W. Watt, Chem. Rev., 46, 324 (1950). 68H. Greenfield, R. A. Friedel and M. Orchin, J. Am. Chem. Soc., 76, 1258 (1954). 69H. Gilman and J. J. Dietrich, J. Am. Chem. Soc., 80, 380 (1958). 140

revealed that no alkali metal cleavages of aliphatic amines are recorded except where the aliphatic carbon bore at least one phenyl group as a

substituent. 70 Thus triphenylmetlyldipheEylamine gave a 66 per cent yield of triphenylmethyl potassium when treated with potassium in ether.

Triphenylamine when treated with sodium in liquid ammonia gave 100 per cent recovery of starting materia1. 70 Treatment of triphenylamine with

sodium powder for a year and a half gave 100 per cent recovery of start-

ing material. The behavior of a typical aliphatic amine, tri-n-butylamine, with sodium in dioxane was therefore investigated.

The reaction of tetrametbylammonium bromide with sodamide was investigated in order to determine whether the intermolecular aIkylations assumed to occur in the reaction of chloromethyltrimethylammonium bromide could be brought about by the action of amide ions on the tetramethylammonium ions produced. 59

Gordon has investigated the reactivity of dioxane with sodium. 71

This experiment was repeated here.

The behavior of cyclopropane under conditions simulating those of 72(a) Gordon was investigated. This was done to show that cyclopropane, if formed under Gordon's reaction conditions, was not converted to propene. Greenfield at al, reported no opening of the cyclopropane ring on treatment of 2-cyclopropylpentent-1 with sodium in liquid ammonia,

70 E. Stoelzel, Ber., 14E, 982 (1941).

7'Gordon, 22. cit., p. 52. 72(a) Ibid., p. 98. 141

either in the presence or absence of ammonium bromide or methanol. 68

Volkenburgh and co-workers have, however, reduced methylcyclopropylketone

by sodium and ammonium sulfate in liquid ammonia to give only 2-pentanone 72(b) and 2-pentanol.

Experimental Details

Attempted Reaction of Butane-1 with Sodium in Liquid Ammonia

Materials.--72.6 ± 0.4 ml. butene-1 (24 ° C) at atmospheric pressure

0.00645 g.-atom sodium

Annaratus.--The usual liquid ammonia apparatus was employed. The butene-1

was introduced from an Orsat gas burette (mercury confining liquid) con-

nected by means of a Y-tube to the ammonia line.

Procedure.--The line from the butene bottle to the Orsat gas burette was

swept with butane. The gas burette was filled twice with butene, then

discharged to the atmosphere. The condensation of liquid ammonia was begun and the stopcock of the gas burette opened to the ammonia line, so

as to admit the indicated amount of butane which probably dissolved in

the liquid ammonia. When 25 ml. of condensed liquid was present in the

reaction tube, the sodium was added. Twenty minutes after this time

when about 50 ml. of ammonia had condensed, the dry ice bath was removed,

and the remainder of the procedure carried out by the usual liquid

ammonia techniques. Gas amounting to 90.8 ml, was obtained from the

reaction, 51.1 ml. of which was unsaturated gas. It is not known what

72(b)R. V. Volkenburgh, K. W. Greenlee, J. M. Derfer and C. E. Boord, J. Am. Chem. Soc., IL 3595 (1949). 142

became of the remaining 21.5 mi. of butane measured as starting material.

It is presumed either that some of the measured volume included some air or that the gas was somehow not actually transferred quantitatively to the liquid ammonia apparatus. The infrared spectrum of the gas from which unsaturates had been removed showed a band in the infrared at

3.46 microns only. By means of the optical density of this band, the yield of n-butane was estimated to be 0.4 + 0.2 per cent, based on butene taken, or 0.7 + 0.3 per cent based on butane recovered. The butane taken was specified 99.5 per cent pure. The butene-1 from the lecture bottle source was found by the method of analysis employed in the foregoing to contain 0.21 + 0.05 per cent n-butane. It therefore appears probable that butene-1 has been reduced in about 0.5 per cent yield.

The Reaction of Isobutene with Sodium in Liquid Ammonia

Materials.--97.9 ml. of gaseous isobutene at 29° and 746 mm. Hg

0.005070 g.-atom sodium

Apparatus.- As in the preceding experiment.

Procedure.--The procedure was essentially that of the preceding experiment. The dry ice bath was kept in place 35 minutes, but gas passed into the collection tube from two minutes after the time that the sodium was added. The quantity of unsaturates found in the evolved gas was

95.1 ml. An optical density of 0.042 at 3.455 microns corresponded to an isobutane yield of 0.15 + 0.015 per cent based on isobutene recovered

(0.14 + 0.014 per cent based on isobutene taken). Isobutene directly from the lecture bottle was found to contain 0.098 + 0.035 per cent 143

isobutane. Thus, no detectable reduction of isobutene by sodium was found.

Attempted Reaction of Tetramethylammonium Bromide with Sodamide in Liquid Ammonia

Materials.--0.003700 mole salt

0.00698 g.-atom sodium

0.0058 g. ferric nitrate

Apparatus.--The usual apparatus for liquid ammonia runs was used. Procedure.--The system was swept with ammonia and the ferric nitrate and sodium added. Liquid ammonia was condensed, but after two hours the sodium blue color persisted. The ammonia was allowed to evaporate; 50 ml. more of liquid ammonia was then condensed and allowed to evaporate.

The apparatus was then allowed to stand overnight (ammonia atmosphere) and the next day 6o ml. of liquid ammonia was condensed in the reaction tube; a colorless solution resulted. The salt was added and the ammonia allowed to evaporate. The gas collected was transferred from an Orsat combustion pipette (mercury confining liquid) through a Drierite tube to an infrared gas cell (system evacuated to stopcock of pipette before admitting sample) and the spectrum taken from 2 to 15 microns. No absorption bands were even faintly apparent.

Attempted Reaction of Tri-n-Butylamine with Sodium in Dioxane

Materials.--0.0977 mole tri-n-butylamine

0.0502 g.-atom sodium

250 ml. dioxane 144

Apparatus.--As described in Chapter IV for dioxane runs. Procedure.--The amine was dried over anhydrous magnesium sulfate overnight. It was then filtered into the Morton flask and the dioxane and sodium added. When the system had come to reflux, the contents of the flask were subjected to high speed stirring for 16 minutes, after which the apparatus was swept with six liters of nitrogen. The gas was analyzed by the usual methods and found to contain no hydrocarbons (absorption band at 3.46 microns absent from spectrum of gas run 2 to 14 microns).

Attempted Reaction of Cyclopropane with Sodium in Dioxane

Materials.--250 ml. dioxane 150 ml. two per cent by volume anhydrous isopropanol in dry dioxane

0.592 g.-atom sodium

Lecture bottle source Matheson cyclopropane

Apparatus. --The usual apparatus for dioxane runs was modified so that cyclopropane would pass in through the side arm of the bearing housing, thence through the sodium-dioxane mixture and up through the Vigreux column

Procedure.--The system was brought to reflux and the stirrer started. Cyclopropane was passed through the apparatus for four hours at an estimated rate of one liter per hour. The isopropanol-dioxane mixture was added in four equal portions at one hour intervals. The stirring was stopped after the last addition due to a sudden agglomeration of the sodium. The system was swept with six liters of nitrogen and the gas analyzed according to techniques described by Gordon, 7 namely 5

absorption of propylene by IBr solution, and absorption of cyclopropane by concentrated sulfuric acid. There appeared to be a contraction (about

one per cent) when a gas sample was treated with IBr, followed by

bubbling through KOH solution to remove bromine vapors. It was, how-

ever, shown that an untreated gas sample shoved a contraction on

treatment with KOH solution alone, indicating a possible physical solubility of the gas mixture in this solution. The absorption by sulfuric acid showed that a total of 3400 ml. of cyclopropane at 26° and 719 mm.

had been subjected to the simulated reaction conditions of Gordon. 72 Even if the IBr absorption of the gas observed is taken to be valid, the maximum conversion of cyclopropane to propylene is only 2.5 per cent.

Reactivity of Sodium with Dioxane Materials.--250 ml. (2.83 moles) dioxane

0.696 go-atom sodium Apparatus.--As described for dioxane runs in Chapter IV. Procedure.--The usual dioxane technique was employed. The particle size did not appear to be as fine as when ammonium salt was present.

Stirring was continued for three hours, after which the system was swept with nitrogen. The spectrum of the products indicated a faint trace of

ethylene (0.008 optical density at l0.54 microns). This would correspond to a 0.03 per cent yield of ethylene based on sodium (2 g. -atoms

sodium required to produce one mole of ethylene) or 0.004 per cent based on dioxane. Thus the ability of sodium to cleave dioxane is very slight under conditions used in this work. 146

CRAPIER X

EVALUATION AND DISCUSSION OF THE REACTIONS OF TETRAALKYIAMMONIUM HALIDES WITH SODIUM

Relative Cleavage Rates of Alkyl Carbanions

A priori, the sequence of stability of the carbanions in increas-

ing order should be 1-009 < sec-009 ;12 iso-C3117 < Er-CO; = 11-C 3R7-

C - < CH due to the destabilizing effect of electron donating alkyl 2 5 3 groups attached to the carbon atom bearing the negative charge. The

opposite order of stability could have been suggested on the basis of

anionic hyperconjugation, 73 namely,

CH CH2 H WA

CH — 1-C 3-4--* CH -c11 3 1 3 CH CH . 3 3

Arguments for this reverse order of stability have been presented by Dessy, Wotiz, and Hollingsworth who found the rate of reaction of

RMgX with hexyne-1 to be proportional to the number of beta-hydrogens on

R. 74) 75 They say that bond breaking is more important to the formation

73H. B. Henbest, Ann. Eut. on Frog. Chem. (Chem. Soc. London), 153, 142 (1956). 74R. E. Dessy, J. H. Wotiz, and C. A. Hollingsworth, J. Am. Chem. Soc., /2, 358 (1957).

75Ibid., 321, 103 (1955). 147

of the transition state, I than is bond making; therefore, the more stable the incipient R 1 the faster the reaction. Seubold presents evidence from the infrared spectra of sodium alkoxides to support the idea of anionic hyperconjugation. 76 Dessy, Hollingsworth, and Wotiz have given the relative reactivities of a number of alkyl- magnesium bromides toward hexyne-1 as follows: CH3MgEr, 6; n-C3H7MgDr,

59; n-C2H5MgDr, 100; iso-C 3H7MgBr, 210; CH2=CHCH2MgDr, 435. 77 They found that the logarithms of these relative reactivities plotted vs. the decomposition voltages of the same Grignard reagents78 gave a linear free energy plot; the decomposition voltages decrease from methyl to allyl. The conclusions of Dessy et al. as to the relative stabilities of carbanions are demanded neither by the mechanism they propose nor by the available evidence.

The weight of recent evidence is in favor of the order of carbanion stabilities given at the beginning of this discussion. Pines and Eschinazi present nearly irrefutable evidence that the methide anion is-more stable than the ethide ion. 79 Thus in the aromatization of

5-methyl-5-ethyl-cyclohexadiene-1,3 by sodiiiM in o-dhlorotoluene at

142-148* ,

76 F. H. Seubold, Jr., J. ag. Chem., 21, 156 (1956). 77R. E. Dessy, C. A. Hollingsworth, and J. H. Wotiz, Am. Chem. Soc., /I, 4410 (1955). 784 . V. Evans, F. H. Lee, and C. H. Lee, ibid., a, 489 (1935). H. 79 Pines and H. E. Eschinazi, J. Am. Chem. Soc., 5950 (1956).

the ratio of methane to ethane is 12 to 1. March has shown that n-

propyl groups cleave at least 38 times (statistically corrected to equal numbers of groups) more readily than isopropyl groups in the pyrolytic cleavage of t-alkoxides, which is considered to be a reverse

Grignard-type reaction: 51

R' R-CONa -+ R-Na + R'COR. 1 R"

Pines and Mark have shown that a primary carbanion must be more stable than a secondary carbanion, which is in turn more stable than a tertiary carbanion. 80, 81 At 292' they found that propylene added benzylsodium

(formed from toluene plus anthracene and sodium) to give principally

isobutylbenzene. They interpreted the addition according to a mechanism requiring the following step:

PhCH2 + ?Due% -* Ph-CH2CH-CH2 - CH CH 3 3

8o H. Pines and V. Mark, J. Am. Chem. Soc., /1 4316 (1956).

81Ibid., 5946 . 149

The addition of benzyl anion to the terminal methylene group of propylene would give the less stable secondary carbanion and lead to n-butylbenzene 80 as product. Benzylsodium added to isobutylene to give neopentylbenzene. Carbanion "chain" reactions catalyzed by the anthracene radical anion gave those products to be expected for the order of carbanion stability primary> secondary> tertiary. Thus, the carbanion dimerization of isobutylene yielded 2,2,4-trimethylpentane on hydrogenation: 81

CH CH 3 i 3 + C=CH2 CH2=C-CH2 -C-CH2 - ' I CH CH &I 3 3 33

The reaction of one mole of isopropylbenzene with 0.2 mole of ethylene catalyzed by potassium t-butoxide gave five times as much ethylated product at 285 ± 31 as did toluene at 291° . 82 Since the reactivities of carbanions are opposite to their order of stability, 73 this is an indication that a benzyl carbanion is more stable than an isopropylbenzene carbanion, even though benzyl carbanions should be more readily formed and presumably exist at higher concentration.

Pines and Schaap found toluene to react with ethylene (potassium- anthracene catalyst) to give a 53 per cent yield of monoadduct in 83 eleven hours; ethylbenzene gave a 61i per cent yield in three hours. These results indicate that an ethylbenzene carbanion (secondary) is

82 H. Pines and L. Schaap, J. Am. Chem. Soc., /24, 2956 (1957). 83 Ibid., 4967. 150

at least 4.4 times as reactive (based on reaction time and yield) as a benzyl carbanion, or that substitution of methyl for hydrogen at a carbanion site is destabilizing in effect.

Mark and Pines found a four to one ratio of isopropyl to n-propylcyclohexane (after hydrogenation) from the reaction of cyclo- hexenyl anion with propylene at 340° .81 This is an indication that

- the primary carbanion CCH- is four times more readily formed e CH 3 than the secondary carbanion CH28HCH3 at this temperature.

Other evidence for the qualitative order of carbanion stabilities is that t-butyllithium or isopropyllithium may be added readily to only 8 one molecule of ethylene. Bartlett, Friedman and Stiles reason that the primary carbanion RCH2CH2 is more stable (less reactive) than the branched carbanion R- . 8

Bryce-Smith found that the yield in aloha-metalation of alkyl benzenes (as opposed to nuclear metalation) decreased as the number of 85 methyl groups on the alpha-carbon increased. He found alpha-metalation to proceed 100 per cent for toluene, 50 per cent for ethylbenzene, and

13 per cent for isopropylbenzene. This may be an indication that addition of methyl groups (in place of hydrogen) to a carbanion site has a destabilizing effect.

84 P. D. Bartlett, S. Friedman, and M. Stiles, J. Am.e. Chem. Soc., 215 1771 (1953). 85 D. Bryce-Smith, J. Chem. Soc., 1069 (1954). 151

Reasons which have been postulated for destabilization of more highly alkylated carbanions are steric strain73, 86 and the electron donating tendency of the attached alkyl groups. ". . .The increase in reactivity [of an alkyllithium] on insertion of a-alkyl groups is due to increased compressions which weaken the carbon metal bond, and at the same time probably augment the ionic character of the bond, and/or to decreased possibilities of stabilization by intermolecular aggrega- 87 tion or solvation. Similar reasons may apply to the observation that cyclopropyllithium adds much less readily ethylene than does .73 isopropyllithium. . 0 it

Hammond has suggested that the order t-C 4.119- > sec-009- 2H 3H7 > n-C4H9 n-C3H7 = c 5 > CH3 for carbanion stabilities iso-C may be due to steric factors. 88 Thus, to accommodate the negative charge as well as possible the unshared electron pair may be in an s orbital, the most electronegative orbital available. This would leave only g orbitals for binding of the three groups to the negative carbon atom and, since these orbitals are 90* to one another, considerable crowding must be present for t-butyl carbanion with least crowding for methyl carbanion. The crowding may be so great in a t-00 9- carbanion that the actual angles are near the tetrahedral value; the resulting sp3 hybridization would place the unshared electron pairs in a less stable orbital. 88

86G. S. Hammond, Steric Effects in Organic Chemistry, Melvin S. Newman (ed.), John Wiley and Sons, New York,' 1956, p. 439.

87H. Hart and J. M. Sandri, Chemistry and Industry, 1014 (1956). 88L. Pauling, Nature of the Chemical Bond Cornell University Press, Ithaca, New York, 1939, p. 86. 152

Hammond86 argues that the inductive effect of a methyl group attached to a saturated carbanion site could possibly be electron withdrawing rather than electron donating. Pines and coworkers consider both steric and polar factors, but emphasize the latter as important in assessing the stabilities of alkyl carbanions. 79-83 From the bulk of evidence cited, the order of carbanion stabilities assumed appears to be correct, with either steric effects or'polar effects (involving the assumption that alkyl groups are electron-donating to carbanions) being of more importance than anionic hyperconJugation in determining alkyl carbanion stabilities.

Gilman and Jones89 found the following products after carbonation of an ethyllithium-n-butyl iodide mixture (-70 ° , 15 minutes): ethyl iodide, n-butyl iodide, 48.0 - per cent yield of propionic acid and 36.4 per cent yield of valeric acid. This would indicate that ethyllithium is about 1.2 times as stable as n-butyllithium at -70', if the assumption that equilibrium was attained under the reaction conditions is admitted, and if any difference in stability of ethyl iodide and n-butyl iodide is neglected. For the corresponding organosodium compounds the factor might be greater than 1.2 because of the greater ionic character of the metal-carbon bond. Gilman, Moore and Baine have measured the relative effectiveness 90 of alkyllithium compounds in ketalating dibenzofuran. In petroleum ether (of b. p. 28-38') after 24 hours reflux followed by carbonation

89H. Gilman and R. G. Jones, J. Am. Chem. Soc., §2.3, 1441 (1941). 90H. Gilman, F. W. Moore and 0. Baine, J. Am. Chem. Soc., 61, 2479 (1941). 153 the yields of 4-dibenzofuran carboxylic acid were: from i-C 3B7Li, 22.5 per cent; from n-C41497,i, 22.6, 30.8, 24, and 23 per cent; from t-C4B 9Li, 32, 34, 31 and 32 per cent. 90 The most reactive alkyllithium is assumed to be the most basic. From the preceding yield data, rate constants may be ca&culated for the rate of reaction of an alkyllithium with dibenzofuran (a second order rate expression is assumed). The inverse of the rate constant for the reaction of an alkyllithium with dibenzofuran is taken as the relative rate of formation of an alkyl carbanion. The relative rates of formation of alkyl carbanions may then be computed to be as follows: (decreasing order); n-C4119 6.9; 1-03E7 , 0.303; sec-C4119 , 0.252; t-C4H9 „ 0.184. Data (of Gilman) for alkyllithium reactivities toward dibenzofuran in diethyl ether9° have not been eon- sidered, due to the reactivity of alkyllithiums toward diethyl ether. 84 The entire series for the relative rates of formation of carbanions 79 79, 89 89, 90 may be given as: 1 100 ; 02H5 , 8.3 ; n-C4H9 , 6.9 ; n-q3B7- , 18.051 ; iso-0 3E7 , 0.30351' 90 ; sec-C4B9 , 0.25290; 1-C4H9 „ 0.184. 9° It should be noted that, in determining the preceding order, the effect of temperature has been neglected. This effect should be to give less selectivity in cleavage of an alkyl group as a carbanion as the temperature increases. It is appropriate at this point to draw inferences concerning the qualitative change from the values given above in relative rates of methyl to alkyl cleavage (as carbanions) when the temperature is changed to the boiling point of dioxane, 101.8 °, and to the boiling point of liquid ammonia, -33 ° . These inferences should prove useful in later discussion. The methyl to ethyl cleavage ratio was 12 to 1 at 142° . 79 At

101.8°, a higher value would be expected due to higher selectivity, and

154

at -33° a still higher value would be predicted. The methyl to n-propyl

and methyl to n-butyl ratios might similarly be expected to be higher at 101.8'.

The methyl to isopropyl ratio expected at 101.8° may be assessed

as follows. At 33° , the iso-C3H7/n-C4H9 ratio was 0.303/6.9 or 0.044.

Due to lower selectivity, this should be less than 0.044 at 101.8'. Then the methyl to isopropyl cleavage ratio is predictable by the expression

CH /C2 >12 1-C 3u = <0.044 = >270. "—7

The ethyl to butyl ratio is assumed to be unity at 101.8', since the

ratio was 1.2 at -70', where higher selectivity would be expected. Due

to higher selectivity at -33°, a still higher ratio is expected for the

methyl to isopropyl ratio at this temperature.

The CH3 /sec-C4 H9 ratio may likewise be predicted as greater than 330 and the CH3/1-C4H9 ratio as greater than 441 at 101.8'. Due to the

operation of selectivity factors, these numbers will be still higher at -33° . The relative rates of cleavage inferred above for alkyl carbanions

must be given more qualitative than quantitative significance not only

because change in temperature changes the selectivity, but also because the reactions cited in assessing these rates must have in several

instances somewhat different transition states. Thus, the relative rates

of formation of carbanions in these reactions must depend in part on factors other than the relative stability of carbanions. It also must

be borne in mind that the reactions with which the reactivity sequence 155

might be compared are likely to have different transition states from

those reactions from which the reactivity sequence was derived.

Relative Cleavage Rates of Alkyl Free Radicals

The order of stability of free radicals is the reverse of that

given in the preceding section for carbanions. This order is, therefore,

in decreasing rank: t-C4H9 > sec-009 iso-C3K7 > n-C4H9 = n-C3H7

C H > CH for groups studied in this work. This order is verified by the 2 5 3 collision yield data of Polanyi, who found the following relative

reactivity of alkyl chlorides toward sodium vapor at 275 ° (methyl taken

as 1): t-C4H9 , 6.7; iso-C 3117, 3.0; E....009 , 3.0; E-C3H7, 2.3; C2H5,

1.4; CH3, 1.0. 91 It is expected that at lower temperatures a higher

selectivity would be shown in the relative tendencies of the free

radicals to form. 92 Abstraction of hydrogen from paraffins by methyl radicals also

gives an idea of the relative tendencies of free radicals to form. The

relative tendencies of free radicals to form under these conditions

can be corrected by means of the Arrhenius equation 93 to temperatures

employed in work done for this thesis. The following order is then

obtained at 101.8° (data statistically corrected to equal numbers of

"active" hydrogens); the relative ability of ethyl to form is taken as

9 W. R. Steacie, Atomic and Free Radical Reactions, Second Edition, Reinhold Publishing Corporation, New York,7§57,75. 769, 771, 772.

92 Ibid., p. 500.

93Ibid., p. 4. 156

unity: t-C4H91 98.4; sec-C 4H91 12.6; C2H5 , 1.0. Similarly, at -33°

1H9, 699; sec-C4H9, 61.2; the following order is calculated: t-C

C2H5, 1.0. The same data indicate that sec-C 4H9 would form at 152 times the rate of C H at -75 ° . 2 5 Recently, the relative rates of formation of t-butyl and isobutyl 94 and of isopropyl and n-propyl have been studied by Rice and Vanderslice.

Their data, corrected to equal numbers of hydrogens and corrected for a deuterium isotope effect, (the deuterium isotope effect is assumed to be identical for primary, secondary and tertiary hydrogens) indicated that isopropyl should form 14.2 times as fast as n-propyl at 101.8 ° and

125 times as fast as n-propyl at -33°. The Arrhenius equations derived from their data were used in obtaining the latter figures. Similarly, t-butyl may be estimated to form 27.8 times as fast as isobutyl at 101.8°

° . and 292 times as fast as isobutyl at -33

As in the case of assessing the relative rates of formation of carbanions, it must be stated that the above relative rates of formation of free radicals could depend in part on differences in transition state in dissimilar reactions. Hence, qualitative rather than great quantitative significance should be placed on these relative rates when dissimilar reactions are used in determining them. Furthermore, the Arrhenius calculations to low temperatures are probably not too reliable, due to change of enthalpy with temperature. The extrapolations to 101.8 ° are probably fair, however.

94 F. 0. Rice and T. A. Vanderslice, J. Am. Chem. Soc., 8o 291 — (1958). 157

Discussion of Results Reaction of unsymmetrically substituted quaternary ammonium halides with sodium.--Methane to alkane ratios statistically corrected to equal numbers of alkyl and methyl groups are given in Table 15. These values were calculated from the methane to alkane ratios listed in Tables 7 and 12 (Chapters VI and VII). If methane is assigned a value of 100 to indicate its relative rate of cleavage from quaternary nitrogen, then the relative abilities of the groups to cleave in boiling liquid ammonia is given by (decreasing order): t-C4H9, 87,600 1.- 20,200; CH3,

100; sec-C41191 41.6 ± 2.9; iso-C 3H7, 13.6 t 0.7; n-C 3H71 1.7 1: 0.1; n-C4119, 0.81i ± 0.06; C2115 , 0.82 t 0.05. The preceding sequence was obtained by averaging all statistically corrected methane to alkane ratios (when these were known to reasonable accuracy) for a given pair of substituents, e. g. methyl and butyl. On the same basis, the relative abilities of the groups to cleave in boiling dioxane is given as t-C4H90 10,750 ± 810; CH3, 100; sec-C4H9, 50.6 t 1.8; iso-C 3H71

2H5 , 4.2 ± 0.1; n-C 3117, 2.4 ± 0.1; n-C1H9, 2.4 t 0.1. 29.0 ±1.4; C The order of cleavage of alkyl groups from quaternary nitrogen is seen to follow the order neither of free radical nor of carbanion stabilities. It is, therefore, suggested that the reductive cleavage may proceed by both a carbanion and a free radical process; the mechanism of the cleavage is dependent on the group cleaved. The relative rates of cleavage may also depend in part on steric factors. The effect of these steric factors on the methane to alkane ratio will also be considered. Table 15. Average Methane to Alkane-Ratios Derived from Reactions of Quaternary Ammonium

Halides with Sodium

a Ratios Salt Boiling Average for given Boiling Average for liquid ammonia methane-alkane pair Dioxane given methane- alkane pair n-Bu3MeNI 148.8 + 4.9 52.4 + 1.3 n-Bu3MeNBr 139.5 + 3.3 46.7 + 1.7 a-Bu2MO2NBr 112.5 + 5.o 119.0 + 8.1 42.4 + 2.1 a-BuMe3NI 117 + 6 33.9 + 1.5 n-BuMe3NBr 92.3 + 10.3 n-BuNe NC1 103.7 + 18.8 36.6 + 3.9 3 s-BuNe Ni 2.42 + 0.17 2.42 + 0.17 1.98 + 0.07 1.98 + 0.07 3 t-BuNe 3N1 0.010114 + 0.00023 0.00114 + 0.00023 0.0093 + 0.0007 0.0093 ± 0.0007 n-Pr Mal 60.9 + 2.4 59.6 + 4.4 3 NI 58.3 + 6.3 41.8 + 4.3 41.8 + 4.3 n-PrMe3 3.45 + 0.17 3.45 ± 0.17 1-Pr?* 3 NI 7.4o ± 0.4 7.34 + o.4 i-PrNO3NBr 7.27 + 0.3 Table 15. (Continued)

Ratios Salt Boiling Average for given Boiling Average for liquid ammonia methane-alkane pair Dioxane given methane- alkane pair

Et3MeNI 126.3 8 -7 25. 6 + 0.3 Et 1■WOr 12306 + 4.8 121.8 + 7.4 3 Et MeNC1 113.4 + 8.7 21.03 + 0.69 24.0 + 1.0 3 EtMe3NI 142 + 131 EtMe NBr 25.4 + 3 2.4

aStatistically corrected to equal numbers of methyl and alkyl groups; + values pre average of recorded deviation in methane-alkane ratios for a given salt. 160

In Table 16 the relative cleavage rates of the groups methyl,

ethyl, isopropyl, and t-butyl are summarized. The ammonium cations

listed in the first line are considered to be homomorphic with the corresponding hydrocarbons listed in the third line. Steric strains have been estimated by Spitzer and Pitzer95 for these hydrocarbons, and are listed in the fourth line. Steric strains in the ammonium ions are assumed to be identical to those in the homomorphic hydrocarbons. The steric strain increases in the order methyl, ethyl,

isopropyl, t-butyl and, therefore, on the basis of steric effects alone the rate of cleavage of these groups from quaternary nitrogen should increase in the same order. On the basis of steric factors, the relative tendency of methyl and ethyl groups to cleave may.be estimated in the following manner: The rate of ethyl cleavage may be given by the Arrhenius equation,

-6AH; /RT Ae zit , kEt and the rate of methyl cleavage by

= Ae 6 Me/1" .

If the assumption is Made that the A factors are identical, then the relative rate is given by

kEtikme = e-(611Et bame)/RT

95R. Spitzer and K. S. Pitzer, ibid., 32„, 1261 (1948).

Table 16, Comparison of Found Alkane to Methane Ratios with Those Predicted on the Basis of

Both Steric Effects and a Carbanion Mechanism.

Cation (u3)1$ CH3CE2N(CH3 )3 (CH3)2CBN(CH3)3 kCH3j3CN(CH3)3/

Group Cleavage of Interest cu3 CH3CH2 (CH3)2CH (cH3)3C

Hamomorphic Hydrocarbon (cH3 )4c CH3CH2C(cn3 ) 3 (CH3 ) 2CBC(CH3 ) 3 (CH3 )3CC(CH3 ) 3 H steric (kcal,/mole) 0.00 (standard) -0.2 2.2 5.0 Steric Difference in Activation Energy for Alkyl and Methyl Cleavage -0.2 0.9 2,2

Predicted Steric RH/CH4, 101.8 ° 0.77 3.3 19

Predicted Anion RE/CH4, 101,8 ° a 0.0834 0.00303 0.0018

Combined Predicted RE/CH4, 101.8 ° 0.064 0.0100 0.0342 b o Found RWC;, 101.8 0.042 0.29 107.5

Predicted Steric RH/CH4 1 ..33° 0.50 6.6 100 330 a Predicted Anion RB/CH4 9 0.0834 0.00303 0.0018

Combined Predicted RH/CH4, -33 0.0+2 0.020 0.18 , b o Found RH/CH4, - 33 0.0082 0.136 876

ad f. section entitled "Relative Cleavage Rates of Alkyl Carbanions". b Reciprocal of average methane-alkane ratio listed in Table 15. 162

and

log(kEt/kme ) = -(45BEt - hame )/2.303RT .

It is assumed that the difference in energy of activation for ethyl and methyl cleavage is due solely to differences in steric strain. These differences are given in the fifth line for various alkane-methane pairs. The difference for ethyl and methyl cleavage was estimated as follows:

The cleavage of ethyltrimethylammonium cation to give ethane and trimethylamine is assumed to release all of the steric strain, 0.2 kcal. Cleavage of methyl groups, however, gives methane and ethyldimethylamine, a homomorph of 2-methylbutane. 2-Methylbutane has a steric strain energy of

-0.2 kca1, 96 and consequently methyl cleavage may be computed to release

0.4 kcal. of strain energy, 0.2 kcal. more than is released in cleavage of ethyl groups. The value for -(a.HE t bHme ) is therefore -200 calories and kEt/kme is 0.77 at 101.8° (374.8° K) and 0.50 at -33°

(240° K). Isopropyltrimethylammonium ion may cleave to propane and trimethylamine so as to release all the strain energy, 2.2 kcal., or it may cleave to give methane and isopropyldimethylamine„ a homomorph of 21 3- dimethylbutane for which a steric strain of 0.9 kcal. is expected according to estimations following the procedure of Spitzer and Pitzer. 95

The heat of formation of 2,3-dimethylbutane at 25° is -42.49 kca1.197

96H. C. Brown and W. H. Bonner, ibid., /2 1 14 (1953).

97E. J. Prosen, K. S. Pitzer, and F. D. Rossini, J. Research Natl. Bur. Stds., 3.1, 403 (1945). 163

whereas that expected is the heat of formation of n-hexane, 97 -39.96 kcal. plus -3.4 (twice the stabilization energy expected for a single iso group95 ) or -43.4 kcal. The steric strain is then (-42.5 + 43.4) = 0.9 kcal. Therefore, 2.2 kcal. of steric strain is lost when isopropyl groups are cleaved and 1.3 kcal. when methyl groups are cleaved from isopropyltrimethylammonium ion. Cleavage of isopropyl groups is, therefore, sterically favored over cleavage of methyl groups by 900 calories, so that a propane to methane ratio based on steric considerations of

3.3 is predicted at 101.8° and of 6.6 at -33°.

The cleavage of t-butyltrimethylammonium ion to give isobutane and trimethylamine is assumed to release all the steric strain, 5.0 kcal. Cleavage to give methane and t-butyldimethylamine would release only 2.8 kcal. of strain, since t-butyldimethylamine is homomorphic with

2,2,3-trimethylbutane, for which a steric strain of 2.2 kcal. is listed.

Cleavage of t-butyl groups is therefore 5.0 - 2.8 = 2.2 kcal. more favorable than cleavage of methyl groups; the predicted isobutane to methane ratio due to steric effects is then 19 at 101.8 ° and 100 at

-33'. The preceding calculations of steric effects assume that all of the steric strain is relieved in going into the transition state and, therefore, the calculations must overestimate the effect of steric strain on rate. In the seventh line of Table 16, the alkane to methane ratio predicted on the basis of the sequence discussed previously for carbanion stabilities is given as "Predicted Anion RH/CH4 ." The eighth line lists the products of the numbers in the sixth and seventh lines and represents the ratio of alkane to methane predictable on the basis of steric 164

factors and carbanion stabilities combined. The numbers in the eighth line are belieVed to represent maximum possible values, since the numbers in the sixth line (predicted steric ratios) are maximum values. The numbers in the ninth line give the actual alkyl to methyl cleavages found in the reductive cleavage of quaternary ammonium salts. The lines 10 through 13 are strictly analogous to lines 6 through 9, but are for the boiling point of liquid ammonia, -33°.

Methyl groups must cleave from quaternary nitrogen by a carbanion mechanism. Only in this way can the much readier cleavage of methyl than all other alkyl groups, except t-butyl groups, be explained.

The possibility of a carbanion mechanism for the cleavage of ethyl groups is now considered. The combined predicted ethyl/methyl ratio in Table 16 is < 0.064 at 101.8° . The value found is 0.042, 0.66 times the maximum number. According to this data, carbanion cleavage of ethyl groups is a possibility. At -33° , the predicted ethyl/methyl ratio is << 0.042 and the found ratio is 0.0082, considered to be good qualitative agreement with the prediction. The agreement is not compelling, but is permissive of a carbanion mechanism.

The possibility of a carbanion mechanism for cleavage of isopropyl groups is considered. The predicted ratio (steric and anion combined) is < 0.0100 at 101.8 ° and the found ratio is 0.29, about 29 times the predicted "maximum" number. At -33°, an isopropyl/methyl ratio of 0.136 is found, and a ratio of << 0.020 was predicted. The ratio found is 6.8 times the predicted ratio. The data do not seem to permit the carbanion mechanism as the major mode of cleavage of isopropyl groups. 165

The possibility that t-butyl groups cleave from nitrogen as

carbanions, but that the release of steric strain in their cleavage is

sufficient to cause the t-butyl group to cleave more readily than

methyl despite the opposite order of carbanion stabilities is now

examined. In dioxane (101.8") Table 16 gives a ratio of < 0.0342 for

the predicted combined t-butylimethyl cleavage ratio, whereas an iso-

butane to methane ratio of 107.5 was found, 3140 times as great. In

liquid ammonia reactions (-33') the maximum predicted ratio is much less

than 0.18 and the found value is 876, at least 4860 times as great.

The conclusion is drawn that t-butyl groups could not have cleaved in

any appreciable proportion from quaternary nitrogen as carbanions.

A summary of the preceding discussion indicates that methyl groups must cleave by a carbanion mechanism, and that t-butyl groups must

cleave by some mechanism other than carbanion. Arguments are presented

that ethyl (and, by analogy, n-propyl and n-butyl groups) cleave by a carbanion mechanism. Although the cleavage mechanism of isopropyl

groups would appear not to be carbanion, no conclusions are drawn as

to the cleavage mechanism of this group pending further discussion.

The possibility of free radical cleavage of some of the groups will now be considered. A carbanion mechanism has been established

above for the cleavage of methyl groups. Therefore, it would be meaning-

less to discuss methyl free radical cleavages. The groups t-butyl,

isopropyl, and/or sec-butyl and ethyl will be discussed.

Since t-butyl groups cannot, according to the previous discussion,

cleave by a carbanion mechanism, it is reasonable to conclude that they

cleave by a free radical mechanism. 166

The possibility that ethyl groups cleave by a free radical mecha-

nism will be examined. From the section entitled "Relative Cleavage

Rates of Alkyl Free Radicals," the predicted ratio of t-butyl/ethyl in a free radical cleavage is 98.4 at 101.8° . The predicted steric ratio may be calculated from Table 16 to be 19/0.77 or 24.8. The combined predicted ratio is then 2440 and the found ratio is 2560, only slightly

in excess of the maximum predicted value. At -33 e , free radical data predict a t-butyl/ethyl ratio of 699, while a steric ratio of 100/0.50 or 200 is predicted; the combined ratio predicted is 140,000. The ratio found is 107,000. It would appear that an appreciable free radical cleavage of ethyl groups is permitted. Arguments will now be presented that the t-butyl/ethyl ratio predicted should have been larger and, therefore, the found t-butyl/ethyl cleavage ratio probably

is not indicative of a free radical mechanism. The data from which the t-butyl/ethyl free radical ratio was predicted is for abstraction 92 of hydrogen by methyl radicals, whereas the present work is concerned with the reaction of quaternary ammonium salts with sodium. A reactant might be considered to be the more selective the lower its reactivity. 98

Comparison of the reaction of isobutane with methyl radicals to give t-butyl radicals and methane with that of t-butyltrimethylammonium,

iodide with sodium to give t-butyl radicals, trimethylamine and sodium shows the latter to be slower when comparison is made on an equal basis.

Thus, from data summarized by Steacie, 92, 99 the reaction rate constant

98J. Hine, Physical Organic Chemistry, New York, McGraw-Hill, 1956, p. 362.

99Steacie, cm. cit., p. 544. 167

for reaction of methyl radicals with isobutane at -33 ° is estimated to -1 -1 be 2 x 103 cm3 mole sec . The rate constant for the reaction of

t-butyltrimethylammonium iodide with sodium is crudely estimated (from

experimental data, assuming a time for half reaction of 90 seconds of

the total time of 210-240 seconds) to be 3 x 103 cm3 mole -1 sec -1 .

Correction of this constant for steric acceleration gives a corrected -2 3 -1 -1 rate constant of 9 x 10 cm mole sec . It would appear, therefore, 4 that the hydrogen abstraction reaction is about 10 times faster than

the sodium reaction when steric acceleration does not enter, and,

consequently, would be expected to be less selective in its action.

The predicted t-butyl/ethyl ratio for a quaternary ammonium salt reacting with sodium should be greater than 140,000 at -33° therefore, and

greater than 2440 at 101.8 ° . Consequently, it is considered that no

appreciable cleavage of ethyl groups necessarily took place by a free

radical mechanism, and that ethyl groups probably cleave from quaternary nitrogen principally by a carbanion mechanism.

The possibility of free radical cleavage of isopropyl groups is

now considered. A calculated ratio of t-butyl to sec-butyl cleavage has been given above for 101.8° and is 7.8. The ratios for t-butyl/

sec-butyl and t-butyl/isopropyl are assumed to be about equivalent. The

predicted ratio of t-butyl/isopropyl cleavage on the basis of steric

effects is 19/3.3 or 5.8 and the combined predicted ratio is 45.2. The

found value is 370, 8.2 times as great. At -33 ° , a maximum ratio of

174 is predicted and a ratio of 6440 is found, 37 times as great. As in

the preceding t-butyl/ethyl comparison, the variation of the found from 168

the predicted ratio is considered to be due to a too low predicted

t-butyl/isopropyl ratio. Thus, at 101.8° the predicted ratio should be

greater than 370 and at -33 ° greater than 174, since the cleavage of

quaternary ammonium salts by sodium should be more selective than

hydrogen abstraction by free radicals. Consequently, it is reasonable

to assign a free radical mechanism for the cleavage of isopropyl, and

by analogy, sec-butyl groups, since the carbanion process has been shown

to be unlikely in the previous discussion of this section.

The preceding discussions must be qualified by a repetition of

the statement that differences in transition states, which, e. may

be more like the products in one type of reaction than in another, may

affect the ratios predicted for relative rates of free radical or

carbanion cleavages.

The following conclusions have been reached concerning the mecha-

nism of cleavage of alkyl groups from quaternary nitrogen. Methyl groups

cleave by a carbanion mechanism, and t-butyl groups by a free radical mechanism. The cleavage mechanism of isopropyl groups, and by analogy

sec-butyl groups, is probably free radical on the basis of semi-

quantitative discussions given above. The cleavage of ethyl groups and by analogy n-propyl and n-butyl groups is probably by the carbanion mechanism.

The qualitative order of cleavage rates of branched groups is

1-00. 9 > sec-C4H9 > iso-C 3H7 in both liquid ammonia and in dioxane in agreement with the order predicted for a free radical mechanism for

cleavage of these groups. On this basis, as well as on the basis of 169

arguments given above, it can be suggested that the cleavage of secondary alkyl groups is (principally) by the free radical mechanism. The order of relative cleavage rates found in dioxane for methyl and primary groups is CH3 > C2H5 > n-C3H7 = 22-C4119, in agreement with the qualitative order predicted for a carbanion process. In liquid ammonia, however, the order was CH3 > C 3H7 > n-C4H9 C2H5 . Since the cleavage rate of n-propyl relative to the other normal alkyl groups is only about two, it is not felt that any meaningful argument can be given for its displacement in the series on changing solvent. The results offer the possibility that these groups cleave by the carbanion mechanism.

In Figure 5, the logarithm of the statistically corrected methane to alkane ratio derived from the reaction of the salt of a given cation with sodium in dioxane is plotted as ordinate vs. the logarithm of the corresponding value from the liquid ammonia reaction as abscissa. The best straight line for the points was found by the method of least squares. The standard deviation in the ordinate values was -10.16 loga- rithmic units. The figure illustrates that there is a linear free energy relationship between the reactions in the two solvents, and that, therefore, the mechanism(s) by which the reactions proceed in the two solvents are probably similar. It would, therefore, appear that there cannot be a change of mechanism, i. e. all the way from carbanion to free radical, on change of solvent.

The effect of varying concentration of salt and of sodium has been studied (Chapter VII). It was found that changing the salt concentration (tri-n-butylmethylam ►cnium bromide in liquid ammonia) has no 170

zw 1 O O z

0 zw

U 0 —1 0

-2

-2 0 1 2

LOG CH4/ALKANE RATIO IN LIQUID AMMONIA

• (n -C4H9)3(CH3)NX (a-C3H7)(CH3)3NX (n -C4H9)(CH3)3NX (iEo-C3H 7)(CH3)3NX o (sec -C4H9)(CH3)3N1 r (C2H5)3(CH3)NX (t-C4H9)(CH 3 )3N1

Figure 5. Comparison of Methane to Alkane Ratios from Cleavage of Quaternary Ammonium Salts in Liquid Ammonia with Those in Dioxane. 171

effect on the methane to butane ratio. Lowering of the sodium concentration caused a slight increase of the methane to butane ratio, almost within the analytical error. The increase is attributable to a lowering of the boiling point of the sodium-liquid ammonia solution as the concentration of dissolved material decreased. It was also found that lowering of the sodium to salt molar ratio led to increased elimination reaction.

The effect of varying the temperature at which a reaction is run has also been investigated. Thus, higher methane to butane ratios were obtained when sec-butyltrimethylammonium iodide or tri-n-butyImethyl- ammonium bromide was reacted with sodium in liquid ammonia at dry ice temperature than at the boiling point of liquid ammonia (Chapter VII,

Table 11). This bears out the idea of greater selectivity of groups cleaved at lower temperatures.

The change in ratio could conceivably also be due to a change in the nature of the liquid ammonia solution as the temperature is lowered.

Work done recently by Fowles and co-workers100 indicates that the solvated electrons in alkali metal-amine solutions exist both paired and unpaired. Lowering the temperature or increasing the concentration favors the pairing of electrons. Unfortunately, the publication of 100 Fowles and co-vorkers does not give sufficient data for computation of the per cent electrons paired under given conditions. It would seem reasonable to suppose then that carbanion cleavage of a quaternary

1000. W. A. Fowles, W. R. McGregor and K. C. R. Symons, J. Chem. Soc., 3329 (1957). 172

ammonium salt would be encouraged by the higher concentration of electron pairs at lower temperature, and a free radical process, which may involve the unpaired electrons, correspondingly discouraged. The increase in methane to butane ratio from sec-butyltrimethylammonium iodide at -78° as compared to that at -33* may be due to this cause in addition to selectivity factors. The lower methane to alkane ratios generally obtained for reactions carried out in dioxane, as opposed to liquid ammonia, and the higher methane to alkane ratio for the reaction of t-butyltrimethylammonium iodide with sodium in dioxane may be attributed to lower selectivity at the higher temperature. The lowering of the methane to butane ratio from tri-n-butylmethylammonium bromide reacted with sodium in dioxane is less than that predicted on the basis of temperature effects (inferred from a plot of log CH4/C010 vs. l/T for ratios taken at -33° and -75° in liquid ammonia). The lowering of the methane to butane ratio from sec-butyltrimethylammonium iodide reacted with sodium in dioxane is also less than predicted on the basis of change of temperature on going from liquid ammonia to refluxing dioxane. These ratios may be rationalized as follows. For homogeneous reaction in liquid ammonia, the rate of cleavage of methyl (rMe ) from quaternary nitrogen as a carbanion may be given by the following expression if it is assumed that the reaction is second order in the concentration of sodium and first order in the concentration of salt (S):

2 _ rme = k (S)(Na) = klasaria2 /rme • 1e 173

In this equation kme represents a measured rate constant for cleavage of methyl carbanions from quaternary nitrogen in terms of concentrations while Ve is the ideal or thermodynamic rate constant expressed in terms of activities. The activities of the salt and sodium are repre- sented by a3 and aNa , respectively, and the activity coefficient for cleavage of methyl groups as carbanions by f . The rate of cleavage Me of an alkyl carbanion (re ) other than methyl may be given by the analogous expression:

2 re m ke (3)(Na) = ktasaLifte .

The relative rate of methyl to alkyl carbanion cleavage is then given by

rme/re = kt f*fik t- Atte C C Me'

The same equation can be derived for the more complex heterogeneous reaction in dioxane. The only terms in the right hand part of the equation which can change on going from ammonia to dioxane are 4' and f each of which should be higher in dioxane than in ammonia, since Me ' ammonia should be better at solvation of anions than dioxane. It is considered that the transition state activity coefficient f is raised somewhat more than the activity coefficient f on going to dioxane Me since a butyl carbanion requires stabilization more than a methyl carbanion. Consequently, the lowering of the methane to alkane ratio on going from ammonia to dioxane due to temperature effects may be offset in part by the poorer solvating power of dioxane for anions. In this manner, the less-than-expected lowering of the methane to butane ratio from the reaction of tri-n-butylmethylammonium bromide with sodium in going from ammonia to dioxane may be rationalized if it is assumed that n-butyl cleaves by a carbanion process.

For the free radical cleavage of alkyl groups, a rate expression first order in sodium is postulated:

ra = kR(S)(Na) = klasaaa/4 .

Here the terms have the same meaning as before and the subscript R denotes free radical cleavage. The relative rate of methyl carbanion to alkyl free radical cleavage may then be given by

rme/ra 22 k1le4,Na/kili •

The higher activity of sodium in dioxane dispersions n (where the activity of sodium may be taken as unity) than of solutions of sodium °

in liquid ammonia (where the activity of sodium must be less than unity since the solutions were not saturated) would tend to make the methane

nThe kinetic equations given apply strictly only for homogeneous reaction. For the heterogeneous reaction upon the surface of sodium, obviously the surface area of the sodium is important in determining the rate of reaction, which should be proportional to the area of sodium. However, the surface area of the sodium cannot be a factor in determining the relative rate of e. t-butyl to methyl cleavage since the same surface is available for cleavage in either direction at any particular time during the reaction. Obviously the availability of electrons at the reaction site is of importance—it would certainly seem that the metal itself would be a richer and more powerful source of such electrons than a dilute solution of the metal. Thus the argument given in the text while not rigorous would appear to be qualitatively correct. o The reacting species in liquid ammonia are probably solvated electrons. Their concentration is taken to be equivalent to the sodium concentration for convenience in discussion. 175

to alkane ratio greater on going to dioxane. The term f the activity RI coefficient for the transition state for cleavage of a free radical, should, since the transition state is uncharged, be approximately independent of solvent; , however, should increase on going to dioxane, Me and thus tend to lower the measured methane to alkane ratio. Evidently the latter effect is less than that due to the increased sodium activity in dioxane, since the methane to alkane ratio from sec-butyltrimethylammonium iodide reacted with sodium in dioxane is higher than predicted on the basis of temperature effects alone as measured in liquid ammonia. For purposes of the preceding discussion, it is assumed that secondary groups cleave by a free radical mechanism. A discussion of the preceding type would also fit tri-n-butyImethyl- ammonium bromide if free radical cleavage of n-butyl groups were assumed.

A possible supplementary explanation for the alteration of the methane to butane ratio for sec-butyltrimethylammonium iodide beyond that expected due to changes in temperature may be as follows. The discrepancy may lie at the lower temperature end of a log CH 4/041110

plot as well as at the higher temperature end. Thus, if the methane to butane ratio at -78° were predicted from the data at -33° and

101.8° , a higher than expected methane to butane ratio would be obtained at -78° . The higher than predicted ratio may be rationalized on the hypothesis the increased electron pairing in the liquid ammonia solu- 96 tion encourages the methyl carbanion cleavage, and/or that decreased 96 concentration of unpaired electrons discourages the sec-butyl free radical cleavage. 176

Evidence for free radicals in the reaction of t-butyltrimethylammonium iodide with sodium.--The isolation of a product, apparently dicumyl, from the reaction of t-butyltrimethylammonium iodide with sodium in cumene is evidence that the reaction proceeded by a free radical 6o process. The fact that the maximum yield of "dicumyl" (1.5 per cent) was less than that of isobutane (17.1 $t 0.5 per cent) was to be expected, on the following basis. 60 An analogous procedure applied by Bryce-Smith for the detection of primary radicals did not necessarily give quantitative yields corresponding to the other free radical product of the reaction. Thus, he obtained only 72 per cent of the theoretical yield of dicumyl expected on the basis of di-n-butyl mercury decomposed in the photolysis of di-n-butyl mercury. The t-butyl radical is more stable than a primary radical, and differs from a cumyl radical only in that a methyl group replaces a phenyl. Consequently, one would expect even less dicumyl in relation to other free radical product, namely isobutane, as was found. The impurity of the "dicumyl" product may be due to alkylation by t-butyl radicals, so that the product may have been in part

CH CH 3 I c-- C I CH CH 3 3 Effect of cation structure on methane to alkane ratio.--The statistically corrected methane to butane ratio in liquid ammonia solution was found to be 139.5 t 3.3 for tri-n-butylmethylammonium bromide, 1)2.5 ± 5.0 for di-in-butyldimethylammonium bromide and 92.3 ± 1003 for n-butyltrimethylammonium bromide. The statistically corrected methane to butane ratio 177

in dioxane solution from n-butyltrimethylammonium iodide was 33.9 + 1.5 while that from tri-n-butylmethylammonium iodide was 52.4 + 1.3. It is

thus apparent that the methane to butane ratio increases with increasing 4 number of butyl groups, as claimed by Blanchard. This increase in methane to butane ratio can be correlated with the order of stability of

the amines formed in the reactions. The order of increasing base

strength for ammonia and the methyl amines in aqueous solution is: 101 NH3, (CH3 )3N, CH3NH2, (CH3 ) 2NH. An analogy is drawn here between

this series and the butylmethylamines; a methyl group is considered to be analogous to a hydrogen in the preceding series, and a butyl group analogous to a methyl. The following order of increasing base strength

is, therefore, postulated for the butylmethylamines: (CH3 ) 3N,

(a-C4H9 ) 3N, (E-009 )(CH3)0, (2-C4H9 ) 2 (CH3 )N. P The order of stability

is of course the opposite of the order of basicity. The pKa values (in aqueous solution) recorded for the R-butyl-methylamines are: (CH 3 ) 3N, 102 103 % 102 )(CH ) 4H9 )2 (CH3 )N, (n-C 9.80; (a-C4H9 )3N, 9.93: ; 4 H9 3 ? 9 10.02; (n-C not recorded. The available data, therefore, agree with the postullted

order of basicities.

In the reaction of tri-n-butylmethylammonium bromide with sodium,

two amines may be formed, tri-n-butylamine and di-n-butylmethylamine.

1°1L. N. Ferguson, Electron Structures of Organic Molecules, Prentice-Hall, Inc., New York, 1952, p. 110.

102N. F. Hall and M. R. Sprinkle, J. Am. Chem. Soc., 54, 3469 (1952).

103J. Hansson, Svensk Kem. Tidskr., 67, 256 (1955).

PHansson„ 103 however, gives the following increasing order of base dissociation constants for the ethyl-methylamines: (CH3)3N, (CH3 ) 2 (C2H5 )N, (CH3 )(C2H5 ) 2N, (C2H5)3N. 178

According to the preceding order, tri-n-tutylamine is more stable than di-n-butylmethylamine;_ consequently, tri-n-butylamine and the corresponding hydrocarbon product, methane, are preferred, leading to a relatively high methane to butane ratio.

In the reaction of di-n-butyldimethylamnonium bromide with sodium, the possible amine products are n-butyldimethylamine and di-n-butylmethylamine. According to the order of stability assumed, cleavage to give the former amine and butane would be preferred, leading to a relative lowering of the methane to butane ratio.

In the reaction of n-butyltrimethylammonium bromide with sodium, the possible amine products are trimethylamine and n-butyldimethylamine.

The trimethylamine is less basics therefore, butane cleavage would be favored, with a relative lowering of the methane to butane ratio. If the pICA increments in the amine basicity series are similar, it would be expected that the methane to butane ratio would be lowered further for this salt (the two possible amines are two members of the series apart) than for di-n-butyldimethylammonium bromide (the two possible amines in the basicity series cited above are neighbors).

An alternate and/or supplementary explanation for the increase in methane to butane ratio with number of n-butyl groups is steric influence on the orientation of the ammonium cation in the transition state. The cation must approach a solvated electron or electron pair in liquid ammonia or a sodium surface in dioxane as a prerequisite to reaction. Addition of butyl groups may render the orientation of the cation sue h that a butyl-nitrogen bond is cleaved more difficultly, 179

without interfering to so great an extent-with orientation favorable for cleavage of a methyl group.

Effect of Anion on methane to alkane ratio.--The methane to alkane ratio derived from reaction of a quaternary ammonium salt with sodium appears to increase on going from chloride to bromide and from bromide to iodide (same cation). Thus, tri-n-butylmethylammonium iodide gave a statistically corrected methane to butane ratio of 52.4 t 1.3 while tri-n-butylmethyIammonium bromide gave a methane to butane ratio of

46.7 ± 1.7 in dioxane. Triethylmethylammonium chloride gave a statistically corrected methane to ethane ratio of 21.0 0.7 while the iodide gave a ratio of 25.6 t 0.3 in dioxane. In liquid ammonia, the halides of the triethylmethyImmmonium cation gave the following statistically corrected methane to ethane ratios: chloride, 113.4 t 8.7; bromide, 123.6 + 4.8; and iodide, 126.3 t 8.7, TheSe values are admittedly the same within the experimental error, but the values cited in dioxane appear to be beyond experimental error. The change in ratio might be rationalized on the basis of an appreciable involvement of ion pairs in the cleavage reaction, particularly in the poor solvating solvent dioxane. Thus, a halide ion in an ion pair might be considered to be associated with the cation so as to shield the methyl-nitrogen bond (less steric hindrance to approach of anion) more than it does an alkyl-nitrogen bond, with consequent favoring of the alkyl-nitrogen cleavage. The methane to alkane ratio would then be expected to be lower the greater the extent of ion pairing. Ion pairing would be expected to be most for chloride, less for bromide, 180

and least for iodide, that is, ion pairing should become less favorable as the size of the anion increases. The observed decrease in methane to alkane ratio from iodide to chloride and from iodide to bromide is in agreement with this discussion, but the magnitude of the effect of changing the anion is small. The values obtained in dioxane reactions are beyond the estimated experimental error, however.

Discussion of elimination reactions.--Elimination reactions to give alkenes in the reactions of tetraalkylammonium halides with sodium have been attributed to the amide ion, BH2- and/or to a carbanion R - in the liquid ammonia reactions. In liquid ammonia, R - should be reduced readily to

RH by NH3, and, therefore, should not be important as a source of eliminative cleavage products.

In the poorer proton-donating solvent dioxane, however, R - may be an important elimination reagent. The only other species causing

Q- G- CH21•CH elimination are the postulated CH2 -CH2 and/or 0 /\\ 0. The con- CH2-C42 centrations of the two latter species would build up only as the reaction proceeds. An alkyl carbanion, as it is a much stronger base than either of the alkoxides shown, might be expected to be largely responsible for the elimination products observed. If the alkyl carbanion were the only cause of eliminative cleavage, no more than fifty per cent of elimination reaction could occur based on salt taken, due to the stoi- chiametric requirements. Greater than fifty per cent elimination reaction to give ethylene was obtained in the case of the reaction of 181

triethylmethylammonium chloride with sodium in dioxane. This is a clear

indication that basic species other than carbanions must operate so as

to cause eliminative cleavage on the quaternary ammonium salt, at least

in the reaction of triethylammonium chloride with sodium in dioxane.

In dioxane, it was noted that less alkene was produced from an

iodide than from the corresponding bromide; also less alkene was produced

from an iodide than from the corresponding chloride in agreement with the 4 observations of Blanchard. The chloride reacted more slowly than the

iodide to give products. This then afforded the alkoxide basic species

in the reaction mixture a longer time in which to react upon the salt,

resulting in higher yields of elimination products. That alkoxide basic

species readily can perform eliminative cleavage reactions on quaternary

ammonium halides has been demonstrated by the reaction of 2-chloroethyl-

trimethylammonium chloride with sodium t-amyl oxide to give only

acetylene and trimethylamine. The rate of reaction of a quaternary

ammonium salt with sodium in dioxane might be related to its solubility.

An iodide is more soluble in dioxane (gives somewhat colored solution)

than is a bromide; a bromide is more soluble than a chloride. Observa-

tions in behalf of this solubility order were made only qualitatively in

connection with the runs, but the order given is believed to be correct.

The more soluble salts may have been better emulsifying agents for the

sodium and therefore may have increased the rate of the reductive

cleavage relative to the elimination reaction. The observed speed,

of a reaction in dioxane is probably a function of the solubility and/or

emulsifying ability of the quaternary ammonium salt reacted with sodium; 182

the greatest elimination reaction then occurred with the least soluble salt in dioxane.

The variation of percentage of elimination reaction in liquid ammonia was due to causes other than change in halide ion; no change in elimination reaction due to halide ion was detectable, due to other variations. Thus, in one case at least, sodium reacted catalytically with ammonia to give sodamide before much reductive cleavage could be accomplished, and principally elimination products dhe to reaction of the amide ion with the salt were observed. It was found that the elimination reaction could be suppressed by increasing the sodium concentration.

Thus, when 0.003173 mole of tri-n-butylmethylammonium chloride was reacted with 0.265 g.-atom of sodium in liquid ammonia, no alkene was detected. Reactions of tri-n-butylmethylammonium bromide with sodium in liquid ammonia showed that elimination reactions increased as the molar ratio of sodium to salt decreased. This indicates merely that the use of sufficiently high concentrations of sodium relative to ammonium salt causes prevalence of reductive cleavage by increasing the competitive chances of such a reaction with eliminative cleavage.

Sources of ethylene and acetylene in dioxane reactions.--Pis previously discussed (Chapter VI), acetylene, when observed in the products from a reaction of a quaternary ammonium halide with sodium in dioxane, is probably derived from basic elimination reactions upon the dioxane.

Thus, acetylene is observed in the products even when tetra-n-butylammonium bromide is the quaternary ammonium salt reacted. 183

It has been shown that ethylene may be derived by action of 104 sodium-potassium alloy on dioxane. The action of sodium on dioxane,

however, gives only minimal amounts of ethylene (if any). It is,

therefore, to be assumed that ethylene, when observed in measurable

quantities, is derived from the quaternary ammonium salt reacted

(when the salt has no ethyl groups) by an intermolecular alkylation process involving the methyl groups . 60 No intermolecular alkylation products (butenes) were detected when tetraethylammonium bromide was reacted with sodium in dioxane.

Effect of reducibility of alkenes in liquid ammonia reactions on methane to alkene ratios.--It has been demonstrated (Chapter IX) that butene-1 may be reduced in about 0.5 per cent yield by sodium in

liquid ammonia. It is, therefore, appropriate to discuss what effect

such a reduction, if it indeed occurs, would have on the methane to butane ratios derived from reaction of quaternary ammonium salts with sodium in liquid ammonia. It is considered that the maximum butane yield from reduction of alkene is 0.5 per cent of the recorded alkene yield (Chapter VII, Table 11). Thus, in Run 6 of n-butyltrimethylammonium bromide, four per cent of the total butane yield (i. e.,

0.04 x % butane obtained) may have been obtained by reduction of alkene. In the reactions of other n-butyltrimethylammonium and sec- butyltrimethylammonium halides, a maximum of two per cent of the butane could have been obtained from this source. In the reactions

l04 Gordon, ok. cit., p. 51. 184

of tri-n-butylmethylammonium bromide as much as eleven per cent of the

butane produced could have came from reduction of butene-1 in Run 7.

This is an extreme case, as the alkene yield was high. As the alkene

yields are usually low in the liquid ammonia reactions, reduction of

alkene cannot be a significant source of alkane in the usual case; the

possibility of alkene reduction should be kept in mind, however, when

examining data for reactions where the alkene yield is greater than

five or ten per cent. Reduction of ethylene and propylene is not

considered as a source of extra alkane, since these two gases have

boiling points higher than that of liquid ammonia. Consequently, the

contact time of these gases with the sodium-liquid ammonia solution must be short, with less chance for reduction to occur. Reduction of

isobutylene is not considered as a source of error, since no evidence

could be obtained for such a reaction in liquid ammonia. Furthermore,

even if isobutylene were reduced to a slight extent, the extra alkane

obtained could lead to only a small error in estimating the isobutane

from reductive cleavage, since isobutane was always produced in high

yield.

Reaction of tetraalkyl ammonium salts of one substituent with sodium.--

The reactions in liquid ammonia of tetra-n-butylammonium bromide,

tetra-n-propyIammonium bromide, tetraethylammonium bromide, and tetramethylammonium bromide were rtudied under apparently comparable condi-

tions of concentration in order to gain an idea of the relative rates

of the reactions, and, hence, get a comparison of cleavage ability of alkyl groups from a source other than the reactions of methyl-alkyl 185

quaternary ammonium salts with sodium. Tetra-n-propylammonium bromide discharged the sodium blue color fastest, tetra-n-butylammonium bromide was next, then tetraethylammonium bromide, and finally tetramethylammonium bromide. All of the salts except tetra-n-butylammonium bromide were only partially soluble in the liquid ammonia at its boiling point.

Th6,relative "rates" measured, then, may just as well have been the relative rates of solUtion of the salts in liquid ammonia (the solution of the salts in the reaction medium is assumed as a prerequisite to reaction) rather than the relative rates of reaction with sodium. In this way the very slow reaction of tetramethylammonium bromide may be rationalized on the basis of its small tendency to dissolve. Otherwise, the order n-propyl cleaves faster than n-butyll which in turn cleaves faster than ethyl is qualitatively identical to that order obtained from the reactions of methyl-alkyl quaternary ammonium salts with sodium in liquid ammonia.

The reaction of t-butyl methyl ether with alkali metals.--Reaction of t-butyl methyl ether with sodium or potassium under various condition0 gave only traces of a reaction product, presumably isobutane. This implies that activation energy for cleavage of a t-butyl group from an ether oxygen must be higher than that for an allyl group, 55 or than that of a triphenylmethyl or diphenylmethyl group, 70 whereas the activation energy for cleavage of a t-butyl group from quaternary nitrogen 58 must be smaller than that for an allyl group.

The change in position of the t-butyl group in the above two reactivity sequences is very likely due to steric factors. Thus, t-butyl methyl ether is analogous to 2,2-dimethylbutane, for which 186

a steric strain of 0.2 kcal. has been listed in Table 16. The steric

strain in di-t-butyl, to which t-butyltrimethylammonium cation is comparable, is 5.0 kcal. 95 Steric strain favoring cleavage of t-butyl

groups is, therefore, about 4.8 kcal. less in t-butyl methyl ether than in t-butyltrimethylammonium cation. According to calculations in which the Arrhenius equation was employed as before this strain energy could lead to a 23,000 fold difference in reaction rate at -33° or a

620 fold difference in reaction rate at 101.8. if all the steric strain is lost in the transition state. On the other hand, allyltrimethylammonium cation should be little, if any, more strained than t-butyl methyl ether and even less strain of the present type should be present in diallyl ether. Therefore, electrical factors are probably more important than steric factors in the cleavage of t-butyl or allyl groups tram ethers.

Steric acceleration in the cleavage of primary alkyl groups from 105 nitrogen.--Haworth? Lunts, and MCKenna have reacted tetrthydro- conessimethine dimethiodide (375 mg.), Et

105R. D. Haworth, L. H. C. Lunts, and J. McKenna, J. Chem. Soc., 3749 (1956). 187

(X = Y = NMe ) with sodium and liquid ammonia to give 18 mg. of allo- 3 pregnane (X = Y = H) and 135 mg. of 313-dimethyIaminoallopregnane (X =

NMe2 , Y = H). They reported no hexahydromoconessine (X = H, Y= NMe 2 ). At the X site, mostly methyl groups of X are cleaved as expected on the basis of the present work. At the Y site the entire Y group was cleaved. The latter cleavage is evidently to be interpreted as a manifestation of considerable steric acceleration, since the complex primary alkyl group was cleaved more readily than methyl. The structure of the compound about the methyl group to which 'ryas attached is somewhat comparable to (but probably more highly strained than) di-t-butylmethane for which 106 Brown and coworkers have estimated a steric strain of 5.3 kcal. It is considered that virtually all this strain energy is lost when cleavage occurs in the direction observed by Haworth et al. Cleavage of a methyl group fit the Y site would leave a structure analogous to 2,2,4- trimethylpentane. Brown and Bonner estimate a release of steric strain of 2.7 kcal. for a cleavage of this type. 107 It would, therefore, appear that cleavage of the alkyl group is favored by at least 2.5 kcal. over cleavage of the methyl group at the Y site; at -33*, steric acceleration would then be at least 170 fold. Since the expected rate of cleavage of three methyl groups versus one n-alkyl group (such as n-butyl) is about

300 to 1 and since Haworth et al. make no report of cleavage of methyl from the group Y, steric acceleration in the present case is evidently greater than 300 fold.

106H. C. Brown, G. K. Barbaras, H. L. Berneis, W. H. Bonner, R. B. Johannesen, M. Grayson and K. L. Nelson, J. Am. (Thei r Soc., 71, 1 (1953). 107H. C. Brown and W. H. Bonner, ibid., 14. 188

CHAPTER XI

EVALUATION AND DISCUSSION OF THE RESULTS OF THE REACTIONS

OF OMEGA-CHLOROALEILTRIMETHTLAMMONIUM HALIDES WITH SODIUM

The reaction of chloromethyltrimethylammonima bromide with sodium.--

The products of and typical yields for the reaction of chloromethyltrimethylammonium bromide with sodium in dioxane are methane (12.2 per cent), ethylene (37.5 per cent), ethyldimethylamine (26.5 per cent), trimethylamine (49.7 per cent), and in some of the experiments, traces of vinyldimethylamine. q All of the amine products observed in this work have also been observed by Blanchard. 14°8 Acetylene was also observed in some of the runs, but it is considered to arise from the action of strong bases on dioxane (Chapter VI). Cbloromethyltrimethyl- ammonium bromide when treated with sodium in liquid ammonia gave ethylene, methane, and tetramethylammonium halide, insofar as the products of the reaction were examined.

The initial reaction is assumed to be

2Na C1CHA(CH3 ) 3 --- -NaC1 + NtEE2W(cE3 ) 3

Some of the methane observed is considered to come from reductive

1°I8Blanchard, 2E. cit., p. 86.

clAccording to the procedures employed, the product reported as vinyldimethylamine may just as well have been N9 ,N',-tetramethy1- 1,2-ethandiamine. 189

cleavage of (CE3)4N derived from the zwitterion. Possible paths by which the reaction may further proceed to give products are as follows:

(I) Wurtz coupling and subsequent elimination to give vinyldimethylamine

by action of base, 109 and the products shown below by reductive

cleavage of the Wurtz coupling product:

(a) (CH3 ) 3t0H2C4(CH3 ) 3 + 2Na reductive cleavage )._

2(CH3) 3N + CH2=CE2 + 2NI

(b) (CH3) 3NCE2CE2t(CE3 ) 3 + 2Na + BH

CH4 + (CH3 ) 2NCE2CH2N(dH3 ) 3 + Na + NaB

(CH3 ) 2NCE:20417(CE ) + 2Na + BE 3 3 (cH3 )licH2cH.3 + NaB + NI or ) (CH3 ) 2NCH2CH2N(CE3 ) 2 + CH4 + Na + NaB;

(II) Intermolecular alkylation: 59

(a) 6E2 ;(0B3 ) 3 + (CE3 )4W cm3cH2N(CR3 )3 + (cn3 ) 3N

Eli2li(cH3 ) 3 + c1cB2ti(Cn3 ) 3 cB3cH21-(CB3 ) 3 + cBeit(cB3 )2c1

(b) B + cH3cH2iii(cH3 ) 3 --->-- cH.2 E2 + (cff3 ) 3N + BH

CH4 CH3CH2N(CH3 ) 2 + BNa + Nat ;

109Blanchard, 22. cit., p. 85. 190

(III) Gamma elimination 110 to give vinyldimethylamine as described by 109 Blanchard or to give ethyldimethylamine by the following process:

4./CH2 (CH ) N I + + (CH ) NCH-CH2: - 3 2 \ 3 2e CH2 1,BH (CH3 )2NCIVH3 + B-;

(IV) Alpha elimination: 111

(CH3 ) 31iCH2C1 + ;176C1 + BH 3 ) 3 + (CH ) N6CHCH + Cl- 3 2 3

(CH ) DECHCH + 2Na 4- 3 2 3 (CH3 )-Ne e CH-CH3 + Na + NaB;

(V) Stevens rearrangement: 112

CH2N(CH3)3 CH3d CH-N(CH3 ) 2

(VI) Methylene radical mechaniam:113' 114

CH2N(cH3 ) 3 ( H3 ) 3N + CH2

nCH2 -->- n/2CH2=CH2 .

11 0F. C. Whitmore, A. H. Popkin, H. I. Bernstein, and J. P. Wilkins, J. Am. Chem. Soc., 63, 124 (1941). 111Hine, 22. cit., p. 131. 112Blanchard, ok. cit., p. 82. 113Hine, op. cit., p. 396. 114Ge Wittig and R. Poister, Ann. 222, 1 (1956). 191

In the above equations BR is any entity of the reaction mixture capable of donating a proton to an intermediate carbanion. This may be the quaternary ammonium salt reacted, or even the dioxane, as demonstrated by the reaction of tri-n-butylmethylammonium iodide with sodium in • dioxane to give only 10 to 20 per cent elimination reaction. If the salt were the only proton source, 50 per cent elimination reaction would be required. B - is any entity of the reaction mixture capable of accepting a proton, either a carbanion or alkoxide derived from attack of carbanions on the dioxane.

Reaction path Ia. to give ethylene cannot be excluded on the basis of present evidence. Although it might be argued from the results of the previous chapter that a two carbon chain should not cleave as readily as a methyl, the effect on the cleavage ability of the trimethylammonio group in the beta position cannot be quantitatively predicted. Indeed, as it is an electron withdrawing group, it may enhance the cleavage ability at the bond indicated. Reaction path ib to give ethyldimethylamine is not favored, since cleavage of a methyl carbanion at the site shown would favor an attack to give vinyldimethylamine and trimethylamine by that methyl carbanion on the neighboring carbon atom which is beta to the remaining quaternary nitrogen.

Reaction path II seems a reasonable mechanism for the production of ethyldimethylamine and ethylene. The production of some ethylene in the reactions of tetraalkylammonium halides (Chapter X) can reasonably be explained only on the basis of this mechanism. The reaction of tetramethylammonium bromide in this work to give ethylene and a trace of ethyldimethylamine in addition to the principle product methane, and of 192

tetramethylammonium chloride by Gordon115 to give ethylene can be explained only on the basis of intermolecular allvlation. The yields of ethylene from these reactions were three and seven per cent; higher yields of ethylene were obtained in the reactions of chloromethyltrimethylammonium bromide with sodium. This is to be expected because the requisite zwitterion, -C4(CR3 )3 must be formed more readily from chloromethyltrimethylammonium ion. Since intermolecular allwlation must occur, some reductive cleavage must occur on the ethyltrimethylammonium ion formed to give principally methane and ethyldimethylamine. Ethyltrimethyl- ammonium bromide (Chapter VI) gave 35-40 per cent ethylene, 52-58 per cent methane and 0.65 to 0080 per cent ethane as products, with a methane to ethane ratio of 7603 ± 7.3. It is to be concluded then that at least some of the ethylene, methane, and ethyldimethylamine observed must arise by reaction path II. No ethane was observed by the usual analytical techniques in Pun 8, (Table 14) but if half the methane there observed came from cleavage of ethyltrimethylammonium ion, ethane would be un- detectable by the infrared analytical method used, Reaction Path III is considered to be unreasonable for the conditions used. An elimination reaction by base is required to form the cyclic ammonium salt shown as an intermediate. The reaction to form zvitterion, however, should be fast, and as discussed in the last chapter, the base concentration in a dioxane-quaternary ammonium salt-sodium reaction mixture must build up only after the reaction has proceeded for some time. The opportunity of forming the intermediate must, therefore,

115Gordon, cit , p. 127. 193

be slight. The further steps postulated on the intermediate seem reasonable, however. Cleavage at the carbon-nitrogen bond shown would release considerable ring strain; hence, this cleavage might be preferred to cleavage of a methyl group.

Reaction Path IV is considered to be unlikely for the same reasons as reaction Path III, namely, the sodium reaction to give zwitterion should be faster than an elimination reaction, and the concentration of base is necessarily low until the reaction has proceeded for a while. Further experimental evidence is required to exclude rigorously paths III and IV to give ethyldimethylamine. Reaction Path V is an eminently reasonable path for the production of ethyldimethylamine. An argument may be presented here to dhow that reaction path II cannot be the exclusive source of ethyldimethylamine. Thus, an exclusive operation of Reaction Path II to give ethyldimethylamine requires a corresponding yield of methane. In Runs 6, 7, and 9 (Table 14) the methane yield is less than the minimum ethyldimethylamine yield, demonstrating that in these runs at least the ethyldimethylamine must have arisen by a path other than II, and, on the basis of the preceding discussion, preferably V. It should be pointed out that the amine yield in Runs 6 and 7 was enhanced by reaction of the residual reaction mixture after the sodium reaction with t-amyl alcohol, favoring and providing indirect evidence for the operation of paths III and IV. However, even when the additional amine yield from this treatment is deducted from the minimum ethyldimethylamine yield (which is surely smaller than the actual 194-

yield) a value of 17.6 per cent is obtained versus an 11.0 per cent yield for methane in Run 7. Reaction Path VI is postulated by analogy with the results of Wittig114 on reaction of tetramethylammonium bromide with phenyllithium to give polymethylene and trimethylamine. No evidence for or against this mechanism was obtained. Tarry residues from the reaction mixtures of the present work proved essentially intractable to study. They probably arise from decomposition products of the dioxane as well as from lubricant of ground-glass joints and of ball-bearings.

Examination of Table 14 will show that the proportions of principal products (methane, ethylene, ethyldimethylamine) vary from run to run, even when carried out under essentially the same conditions. No ready explanation is available for this, except possibly the compe- tition of mechanisms I, II, and V being subject to very slight changes in conditions, for example stirring rate or percentage of residual water in salt after drying. The rather low yields of ethylene and methane in the liquid ammonia runs indicate that either ethyldimethylamine is formed readily in this medium or that a good proportion of the salt is reduced to tetramethylammonium ion which did not react completely due to insufficient concentrations of sodium employed. The latter explanation is favored by the identification of tetramethylammonium ion in the residue from one of the reactions.

The reaction of 2-chloroethyltrimethylammonium chloride with zinc dust and with sodium t-amyl oxide.--Gordon 116 has reacted 2-chloroethyltrimethylammonium chloride with sodium to give ethylene and trimethylamine, and

11 6Ibid., p. 40. 195

postulated an ordinary concerted type elimination reaction of abstraction of the beta-halogen by sodium. Similar qualitative results were obtained in this work upon reaction of the salt with zinc dust in aqueous ethanol (Chapter VIII). Residual salt from the reaction was physically dissimilar to the starting material. On conversion to the hydroxide and pyrolysis it gave acetylene but no ethylene. It is, therefore, concluded that there was no ethyltrimethylammonium halide in the reaction residue, which would have been obtained had there been any protonation of an intermediate beta-carbanion. The salt isolated is most suitably a vinyltrimethylammonium halide, probably the iodide. This could have arisen by means of an elimination reaction on 2-chloroathyltrimethyl- ammonium chloride, Sodium carbonate present in the reaction mixture could have rendered it suitably basic to perform this elimination reaction, which would be preferred in the direction postulated. 109 The stronger base, sodium t-amyl oxide, was found upon reaction with 2-chloroethyltrimethylammonium chloride to eliminate not only hydrogen chloride but also trimethylamine. Acetylene was the only observed hydrocarbon product in this reaction. No acetylene was observed in the zinc-aqueous ethanol reactions.

The reaction of .5-chloroamyltrimethylammonium chloride with sodium in dioxane.--The salt 5-chloroamyltrimethylammonium chloride on reaction with sodium in dioxane gives the following products: methane (39.6 per cent), pentene-1 (29.7 per cent), some ethylene, x-pemtenyldimethyl- amine (8.8 per cent), n-amyldimethylamine (29.1 per cent), trimethylamine (4003 per cent, and a trace of saturated hydrocarbon other than methane, probably n-pentane (0.31 per cent), but possibly cyclopentane. 196

There was also 0.2 to 0.3 per cent yield of ethyldimethylamine in Run. 3, which probably arose by intermolecular alkylation processes discussed above. The methane doubtless arises from a reductive cleavage reaction

as discussed at length in the last chapter. The pentenyldimethylamine probably arises by dehydrochlorination

followed by reductive cleavage of the resulting pentenyltrimethylammonium

ion. The rest of the products can be explained on the basis of reduction of the omega-chlorine to give n-amyltrimethylammonium chloride,

followed by elimination and reductive cleavage reactions of the type

discussed in Chapter X. We may, therefore, compare, the reaction to that of n-butyltrimethylammonium chloride with sodium in dioxane (Table 7), where the proportions of products alkene:methane:alkane were 1:1.35: 0.0014. The corresponding proportions for the reaction of 5-chloro-

amyltrimethylammonium chloride were 1:1.33:0.00101i (Run 3). It would appear, therefore, that with the exception of pentenyldimethylamine,

all the products result by processes of the type discussed in Chapter X.

The processes set forth by Gordon ' are, therefore, unlikely as progeni-

tors of the products observed from reaction of this salt with sodium in dioxane. Comparison of reactions carried out pi Gordon on amega-chloroalkyltrimethylammonium halides with the analogous tetraalkylammonium salts.--

Gordon's reaction117 of 4-chlorobutyltrimethylammanium chloride with sodium in dioxane gave butene-1 in 57 per cent yield and methane in ten per cent yield. Butadiene was absent from the products. It would

1171bid., p. 128. 197

appear that processes other than those of reduction to n-butyltrimethylammonium chloride, and subsequent simple Hofmann elimination and Emde- type degradation reaction, operated. It should be stated, however,

that Gordon's conditions were such as to favor reduction of the omega halogen and Hofmann elimination. Conditions of Gordon favoring elimination reactions (as opposed to reductive cleavage) are the long reaction time (11 hours) employed which would encourage build-up of the base concentration. Essentially the same comments apply to Gordon's reaction 118 of 3-chloropropyltrimethylammonium choride, Conditions further favoring reduction to n-propyltrimethylammonium chloride was the addition of isopropyl alcohol early in the reaction. The sodium isopropoxide formed would also favor increased elimination reaction to give propylene.

The preceding discussion is principally to point out an additional mechanism or reaction path to those postulated by Gordon) Protonation of the omega-carbanion by dioxane was not considered by him to be likely, probably principally due to the sluggish reaction of tetramethylammonium chloride with sodium in dioxane. Results given in this thesis, however,

indicate that dioxane must be a good proton donor to carbanions, as otherwise the production of saturated gaseous hydrocarbon products from, e. n-butyltrimethylammonium chloride would be sluggish. 198

CHAPTER XII

CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK

Conclusions.--The relative abilities of alkyl groups from methyl to t- butyl to cleave from quaternary nitrogen on reaction with sodium have been determined. Except for small differences among the normal alkyl groups, ethyl through n-butyl, the relative rates of cleavage are qualitatively the same in boiling liquid ammonia and in boiling dioxane. The relative rates of cleavage of branched alkyl groups indicate that these groups cleave principally by a free radical mechanism. The cleavage of branched groups, in particular t-butyl, appears to be accelerated by steric factors. Comparison of predicted With found alkane/methane ratios makes it doubtful that any large proportion of t-butyl groups cleave by a carbanion mechanism. Methyl groups must cleave from quaternary nitrogen by a carbanion mechanism, since they are cleaved from quaternary nitrogen faster than normal or secondary alkyl groups. The mechanism of cleavage of ethyl, n-propyl, and n-butyl groups, while less definite, is probably also via the carbanion process.

The statistically corrected methane to butane ratio from the reaction of a quaternary ammonium salt bearing both methyl and butyl groups with sodium has been shown to increase with increasing number of butyl groups when the reaction was run in either dioxane or liquid ammonia.

The methane to alkane ratio from an ammonium salt of given cation has been shown to increase from the chloride to the bromide to the iodide 199

when the salts are reacted with sodium in dioxane, but not (within the experimental error) in liquid ammonia.

A linear relationship of free energies of activation exists between the methane to alkane ratios obtained in liquid ammonia and those

Obtained in dioxane for the reaction of quaternary ammonium halides with sodium.

Intermolecular methylation occurs to a small extent on the reaction of tetraalkylammonium halides bearing methyl groups with sodium.

Amide ion is not a sufficiently strong base to bring about intermolecular methylation in liquid ammonia. No intermolecular alkylation occurs so as to involve ethyl groups attached to quaternary nitrogen in reactions with sodium in dioxane.

A Hofmann-type elimination reaction competes with the reductive cleavage reaction in the treatment of tetraalkylammonium halides with sodium in dioxane. More elimination occurs with chlorides than bromides and with bromides than iodides. The slower a reaction, the greater is the percentage of products of elimination. Ethyl groups attached to quaternary nitrogen may be eliminated by bases other than carbanions in dioxane.

Dioxane is a good proton donor to alkyl carbanions. Dioxane is only very slowly cleaved by sodium to give traces of ethylene. Acety- lene, observed in the hydrocarbon products of the reaction of tetraalkylammonium halides with sodium, arises by eliminative reactions of intermediate carbanions on the dioxane.

Evidence has been Obtained that t-butyl methyl ether is cleaved very slowly by sodium in liquid ammonia or in cumene or by potassium in 200

dioxane to give isobutane. The slowness of the reaction is attributable in part to a lack of steric acceleration of t-butyl cleavage.

The reaction of 2-chloroethyltrimethylammonium chloride with active metals to give ethylene and trimethYlamine . is a coneettedrprocess, analogous to an ordinary beta-elimination reaction. 2-Chloroethyltri- methylammonium chloride readily undergoes reaction with sodium t-amyl oxide to give acetylene and trimethylamine.

Most of the products of the reaction of 5-chloroamyltrimethylammonium chloride with sodium can readily be rationalized as arising from its reduction product, n-amyltrimethylanmionium chloride.

Of several possible paths for the formation of ethyldimethylamine on reaction of chloromethyltrimethylammonium bromide with sodium, intermolecular alkylation followed by reductive cleavage is particularly favored by the evidence. An intramolecular process, most suitably a

Stevens rearrangement, must also be important in the production of ethyldimethylamine.

Of several possible paths for the production of ethylene from the reaction of chloromethyltrimethylammonium bromide with sodium, intermolecular alkylation followed by Hofmann elimination is favored by the evidence. The other paths have not been excluded.

The reactivities of some of the products have been examined.

Butene-1 is reduced by sodium in liquid ammonia to give no more than 0.5 per cent n-butane under the conditions examined. Isobutene is not reduced under these conditions. Cyclopropane is not appreciably converted to propene on contact with highly dispersed molten sodium in 201

dioxane, Commercial t-amyl alcohol contains impurities which react

slowly with sodium to give volatile hydrocarbon products. Tri-n-

butylamine is not reductively cleaved by sodium in dioxane to give

butane or any other saturated hydrocarbon,

Suggestions for future work.--The order of ability of the normal alkyl

groups ethyl, n-propyl, and n-butyl to cleave from quaternary nitrogen

should be determined with greater certainty. This might most readily be

achieved by reaction with sodium of n-butyltri-n-propylammonium iodide

and triethyl-n-propylammonium iodide under conditions employed in this work. Neither hydrocarbon cleavage product would be expected in very

small yield, and, consequently, the infrared analytical method of 119 Stroupe should be applicable.

Kinetic studies should be carried out on the reaction of t-hutyl-

trimethylammonium iodide with sodium in liquid ammonia which should give

a reaction first order in sodium (or ammoniated electrons) if it is truly

a free radical process. Kinetic studies on n-butyltrimethylammonium

iodide should give a reaction second order in sodium (or ammoniated elec-

trons) for a carbanion process. The rates might be followed spectrophoto- 120 metrically, or, if they prove very rapid, by a flow technique. The

elimination reaction could be suppressed by working with appropriate

sodium concentrations, or corrected for by product studies made under

119J. D. Stroupe, Anal. Chem. 22, 1125 (1950).

120A. A. Frost and R. G. Pearson, Kinetics and Mechanism, A Study of Homogeneous Chemical Reactions, New York, John Wiley and Sons, Inc., 1953, pp. 183-186. 202

comparable conditions. If practicable, tetra-n-alkylammonium halides, ethyl through n-butyl, should be studied in a similar manner, in order to show that one distinct (free radical or carbanion) mechanism is or is not responsible for cleavage of normal alkyl groups. An experimentally easier method for elucidating the nature of the reaction of t-butyltrimethylammonium iodide with sodium might be as follows. Reasoning has been presented (Chapter X) that, if the alkyl group on a quaternary ammonium halide is cleaved by a free radical mechanism, then the methane to alkane ratio from reaction of the salt with sodium in liquid ammonia should vary as the sodium concentration. It is, therefore, suggested that this assertion be tested by means of the reaction of t-butyltrimethylammonium iodide with sodium in liquid ammonia, and if meaningful results are obtained, that the reactions of isopropyltrimethylammonium iodide and sec-butyltrimethylammonium iodide might be studied in a similar manner.

Dioxane has been shown to be a good proton donor to alkyl carbanions. Consequently, it is probably not a suitable solvent for studying + the reactions of most salts of the type Cl(CR 2 )nN (CR3 ) 3CI with sodium, particularly those where it is equal to or greater than three. It is recommended that the reactions of salts where n = 3 to 5 be repeated in solvents having less proton donor ability. Potassium in tetrahydrofuran or in benzene is possibly suitable. The proton donor ability of the medium could be tested by attempting the reaction of tetra-n-butylammonium bromide with potassium therein. The production of butane in greater quantity than butene-1 would indicate a solvent too reactive toward carbanions to be suitable for the study of the reaction. Equal 203

yields of butane and butene-1 could conceivably be obtained by the reaction: _ C4119 + (C4H9 )4NBr C4H10 + CL H + (CLH N + Br . 4 8 4 9 ) 3

The butane yield would also be a good measure of the extent of intermolecular elimination reaction which could be brought about by an omega anion from an omega-chloroalkyltrimethylammonium salt, considered to be analogous to an alkyl carbanion.

Radioactive labelling offers possibilities for distinguishing some of the mechanisms not readily assignable on the basis of work done for this thesis. Thus labelling of C1CH2N(CH 3 )3Br as shown by the * * asterisk would give ethylene of greater activity (CH 2-CH2 ) by the Wurtz coupling mechanism (Chapter XI, Reaction Path I) than by the intermolecular alkylation mechanism (Reaction Path II) which would give three parts * * CH2=CH2 and, at most, one part CH2=CH2 . It should be pointed out that the Wurtz coupling mechanism and the methylene radical mechanism (Path

VI) are indistinguishable by this method. The methylene radical mechanism (Path VI) was postulated by analogy with the results of Wittig, who obtained polymethylene from the reaction of phenyllithium with tetra- 114 methylammonium bromide. His sealed tube conditions would, however, favor the formation of polymethylene (polyethylene) by the reaction

Ph nCH2=CH2 ---P-Ph(CH2CE2 )n_iCH2CH;.

It is consequently felt that the methylene radical mechanism is improb- able for the formation of ethylene, and the mechanisms to be established are the Wurtz coupling and/or intermolecular alkylation mechanisms. 204

It has been observed in general that tetraalkylammonium halides seem to increase in solubility in dioxane and are less hygroscopic in the order chloride, bromide and iodide. It is suggested from the stand- point of preparation and handling that omega-chloroalkyltrimethylammonium iodides or bromides would be just as suitable for continued study of the reactions of the omega-chloroalkyltrimethylammonium ion as the corresponding chlorides. The use of iodides, if this leads to improved solubility in the media employed, should also lead to shortened reaction times. 205

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19. Ibid., p. 25.

20. Ibid., p. 18.

21. Ibid., p. 88.

22. Ibid., p. 87.

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45. A. W. Francis and S. J. Lukasiewice, Industrial and Engineering Chemistry, Analytical Edition, 6, 703 (1945).

46. Blanchard, 2E. cit., p. 101. 47. Blanchard, E. cit., p. 45.

48. Blanchard, op. cit., pp. 36-40.

49. W. G. Johnson and W. C. Fernelius, Journal of Chemical Education , 6, 441 (1929).

50. Blanchard, E. cit., p. 9.

51. J. March, Ph. D. Thesis, Pennsylvania State University, 1957; Dissertation Abstracts, 17, 959'(1957).

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54. Ibid., p. 987.

55. A. J. Birch, Quarterly Reviews (London), 4, 69 (1950). 208

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57. R. L. Letsinger and J. G. Traynham, Journal of the American Chemical Society, 70, 3342 (1948).

58. Gordon, 2E. cit., p. 124.

59. Gordon, 22. cit., p. 26.

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61. H. Tropsch and W. J. Mattox, Industrial and Engineering Chemistry, Analytical Edition, 6, 104 (1934).

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67. G. W. Watt, Chemical Reviews, 46, 324 (1950).

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69. H. Gilman and J. J. Dietrich, Journal of the American Chemical Society, 80, 380 (1958).

70. E. Stoelzel, Berichte der deutschen chemischen Gesellschaft, 74B, 982 (1941).

71. Gordon, E. cit., p. 52.

72. (a) Ibid., p. 98 (b) R. V. Volkenburgh, K. W. Greenlee, and C. E. Boord, Journal of the American Chemical Society, 71, 3595 (1949).

73. H. B. Henbest, Annual Reports on the Progress of Chemistry (Chemical Society of London 77737742 (1956

74. R. E. Dessy, J. R. Wotiz, and C. A. Hollingsworth, Journal of the American Chemical Society, 79, 358 (1957). 209

75. Ibid., 77, 103 (1955).

76. F. H. Seubold, Jr., Journal of Organic Chemistry, 21, 156 (1956).

77. R. E. Deasy, C. A. Hollingsworth, and J. Wotiz, Journal of the American Chemical Society, 77, 4410 (1955).

78. w. V. Evans, R. H. Lee, and C. H. Lee, ibid., 57, 489 (1935).

79. H. Pines and H. E. Eschinazi, ibid., 789 5950 (1956). 80. H. Pines and V. Mark, ibid., 78, 4316 (1956). 81. Ibid., 4967.

82. H. Pines and L. Schaap, Journal of the American Chemical Society, 799 2956 (1957). 83. Ibid., 4967.

84. P. E. Bartlett, S. Friedman and M. Stiles, Journal of the American Chemical Society, 75, 1771 (1953).

85. D. Bryce-Smith, Journal of the Chemical Society, 1079 (1954). 86. G. S. Hammond, Steric Effects in Organic Chemistry, Melvin S. Newman (ed.), New York, John Wiley and Sons, Inc., 1956, p. 439. 87. H. Hart and J. M. Sandri, Chemistry and Industry, 1014 (1956).

88. L. Pauling, Nature of the Chemical Bond, Cornell University Press, Ithaca, N. Y., 1939, p776. 89. E. Gilman and R. G. Jones, Journal of the American Chemical Society, 63, 1441 (1941).

90. H. Gilman, F. W. Moore and O. Baine, ibid., 2479.

91. E. W. R. Steacie, Atomic and Free Radical Reactions, Second Edition, Reinhold Publishing Corporation, New York, 1954, pp. 769, 771, 772.

92. Ibid., p. 500.

93. Ibid., p. 4. 94. F. O. Rice and T. A. Vanderslice, Journal of the American Chemical Society, 80, 291 (1958).

95. R. Spitzer and K. S. Pitzer, ibid., 70, 1261 (1948).

96. H. C. Brown and W. H. Bonner, ibid., 75, 14 (1953). 210

97. E. J. Prosen, K. S. Pitzer and F. D. Rossini, Journal of Research of the National Bureau of Standards, 34, 403 (1945). 98. J. Hine, Physical Organic Chemistry, New York, McGraw-Hill, 1956, p. 362. 99. Steacie, E. cit., p. 544. 100. G. W. A. Fowles, W. R. McGregor, and M. C. R. Symons, Journal of the Chemical Society, 3329 (1957). 101. L. B. Ferguson, Electron Structures of Organic Molecules, Prentice- Hall, Inc., New York, 1952, p. 110. 102. N. F. Hall and M. R. Sprinkle, Journal of the American Chemical Society, 54, 3469 (1952). 103. J. Hanmson, Svensk Kemisk Tidskrift, 67, 256 (1955). 104. Gordon, 2E.. cit., p. 51. 105. R. D. Haworth, L. H. C. Lunts and J. McKenna, Journal of the Chemical Society, 3749 (1956). 106. H. C. Brown, G. K. Barbaras, H. L. Berneis, W. H. Bonner, R. B. Johannesen, M. Grayson and K. L. Nelson, Journal of the American Chemical Society, 12, 1 (1953). 107. H. C. Brown and W. H. Bonner, ibid., p. 14. 108. Blanchard, 2E. cit., p. 86. 109. Blanchard, op. cit., p. 85. 110. F. C. Whitmore, A. H. Popkin, H. I. Bernstein, and J. P. Wilkins, Journal of the American Chemical Society, 63 124 (1941). 111. Hine, op. cit., p. 131. 112. Blanchard, 2E.. cit., p. 82. 113. Hine, E. cit., p. 396. 114. G. Wittig and R. Polster, Justus Liebigs Annalen der Chemie, 599, 1 (1956). 115. Gordon, E. cit., p. 127. 116. Ibid., p. 40. 117. Ibid., p. 128. 211

118. Ibid., p. 101.

119. J. D. Stroupe, Analytical Chemistry, 22, 1125 (1950). 120. A. A. Frost and R. G. Pearson, Kinetics and Mechanism, A Study of Homogeneous Chemical Reactions New York, John Wiley and Sons, Inc., 1953, pp. 183-186. 212

VITA

The author was born October 22, 1930 in Philadelphia, Pennsyl- vania. His parents are William Stevenson and Evelyn Fisher Stevenson.

He attended grammar school at Willow Grove and Hatboro, in the suburban

Philadelphia area, and high school at Hatboro. He entered the University of Pennsylvania in September of1948, and graduated with a B. S. in

Chemistry in June of 1954. The author, an enlisted member of the Naval

Reserve at the outbreak of the Korean conflict, served on active duty with the U. S. Navy (Atlantic Fleet) from January 24, 1951 to October 9,

1952. In September of 1954, he entered the Graduate School of the

Georgia Institute of Technology to study for the degree of Doctor of

Philosophy in Chemistry, On June 18, 1955, he married the former

Marian Irvine of Bryn Mawr, Pennsylvania. The author is the father of one child, Marian Evelyn, born June 22, 1957, in Atlanta, Georgia. The author was a member of the Alpha Iota Chapter of Alpha Chi Sigma at the

University of Pennsylvania and is a member of The Society of the Sigma Xi at the Georgia Institute of Technology. He has accepted employment with the Celanese Corporation at Summit, New Jersey.