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LSU Historical Dissertations and Theses Graduate School

1954 A Study of Some Nitroso Compounds. Cilton Watson Tate Louisiana State University and Agricultural & Mechanical College

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Recommended Citation Tate, Cilton Watson, "A Study of Some Nitroso Compounds." (1954). LSU Historical Dissertations and Theses. 8076. https://digitalcommons.lsu.edu/gradschool_disstheses/8076

This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Historical Dissertations and Theses by an authorized administrator of LSU Digital Commons. For more information, please contact [email protected]. A STUDY OF SOME MXTROSQ COMPOUNDS

PART I * Oxidation of Nitroso Compounds to the corresponding Mitro Cosh pounds.

PART IX - Development of Chromat©graphic and Spectrophotoiaetric Methods for the Separation, Identification and Estimation of some Mitros© and Related Compounds.

PART XXX- Influences of Mitre Compounds on the Decomposition of Nitroso Compounds.

A Dissertation

Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy The Department o f Chemistry

by C ilton Watson Tate M.S. Louisiana State University, 1950 Aug., 1953 UMI Number: DP69454

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LOUISIANA STATE UNIVERSITY LIBRARY

119-a 2- i S2P0 ACKNOWLEDGrMEWT

The author wishes to express hie sincere appreciation to Or* W.R.

Edwards, who directed this work for his aid and encouragement, and to

Ore* A.R. Choppin and Joseph Reynolds fo r th e ir l& endiy suggestions* y He i s also indebted to Mr* Oct&vious Pasqual fo r his a ssista n ce , and to

Mrs* John H* Tate for help in preparing the manuscript*

The author wishes to express his appreciation to the Bureau of

Ordnance, Department of the Maty and the Office of Ordnance Research,

Department of the Amy, whose financial assistance made this work

possible*

i i ABSTRACTS

Fart I - The objects of this part of the work wore (1) to study the effectiveness of hydrogen peroxide as an oxidant for th© conversion of n itro so eempouads i n general to n itr e compounds ( 2 ) to study the effects of possible variations in the conditions upon the progress of such oxidations. Previous work of th is s o rt has consisted o f a lim ite d number of isolated experiments, the reports of which gave little information suitable for the selection of optimum conditions ibr the reactions they described*

Five aromatic nitroso compounds (four phenols mid one amine) were studied, with most attention being given to p-nitrosophenol, One aliphatic nitroso compound received similar study* It was found that hydrogen peroxide was generally satisfactory as an oxidant for the aromatiee studied,

(presumably for aromatic nitroso compounds in general) and apparently su­ perior to other oxidants, as far as the latter have been examined* In the ease of the single aliphatic nitroso compound studied, hydrogen per­ oxide was found to be inferior to chromic acid*

In the study of p-nitrosophenol, i t was observed that a maximum conversion to p-oitrophenol approaching 90$ could be attained* Extension of the time of exposure of reaction mixtures to hydrogen peroxide led in every case to a progressive loss of some of tbs nitre compound Initially formed.

It was also observed that as the concentration of the peroxide, and/or the temperature was increased, the time required to reach the maximum yields was shortened* but within the ranges covered in this study, the amounts of such maximum yields did not vary greatly*

Examination of the other aromatic nitroso compounds was less thorough*

i l l but as far as it went* the results obtained were similar to those obtained with p-aitro* ophenol* When nitropropane wee oxidised with hydrogen peroxide, much smaller yields, ranging firm £ to 35SS. were obtained; the maximum yield being obtained only under narrow conditions of temperature and concentration*

This compares with an 83$ possible yield when using chromic acid*

P art U - The objects of thia part of the work were (l) to study the chromatographic and spectrophotometric characteristics of some selected n itr o , n itro so , amino, aso, and azoxy compounds; ( 2 ) to develop (and to study the effectiveness of) chromatographic and spectrophotometric pro* eedures for the identification, separation, and quantitative estimation of these compounds in solutions containing one or more of them* The re la tiv e rate s o f movement of these compounds on standard chromatographic columns were determined* By varying the adsorbents, the solvents, and the developing solutions, sufficient data were obtained to make possible the separations*

For those compound* whioh gave a colorless seme, methods for locatlr^ the sons m the column were developed* The sensitivities, or the mini* sum ecncentrations necessary to give sones which could be discerned, were ascertained fo r sev eral o f them*

Solutions o f known concentrations of the individual compounds in absolute ethyl alcohol were made up and the absorption curves of these solutions were obtained on a Beckman Model D.U. Quartz Spectrophotometer.

Solutions of known concentrations of the individual compounds, and mixtures of two or more of the compounds, were made up in the proper sol­ vents, and separated on a chromatographic column* The zones, were cut out, dried, eluted, ml the solutions obtained diluted to the desired volume* The concentrations of these solutions were determined, using iv the Beckman Spectrophotometer and the standard curves which had been obtained as described* From the results obtained, it was concluded that ehromatographic and speetrophotcmetric techniques could be used as an efficient method lor the separation, partial identification, and estimation (with a range of error of approximately ^2%) of these compounds in mixtures*

The objects o f th is work were (1) to s tudy the in te ra c tio n s, i f any, o f n itro confounds with n itro so compoundsi ( 2 ) to study any influences (exerted by interaction or otherwise) of nitro compounds upon

the thermal and/or photochemical decomposition of nitroso compounds.

The nitroso compounds studied in this part of the work were p-nitrosophenol and p-nitrosodimethyleniline. The nitro compounds used included nitrobcnsene, p*ehlor onitrobensene, p~nitrotoluene, p~nitro~ phenol and p-nitrobenaoie acid.

In the ease of the amine i t was found that* there was some evidence of interaction, but that i t was usually small compared to the spontaneous decomposition of the n itro so compound. The extent o f the in te ra c tio n varied with conditions, being negligible or marly so under mild conditions, but more conspicuous under severe conditions of light or temperature. The oxidation of the nitroso compound to the analogous nitro compound, pre­ sumably by the oxidation action of the nitro compound in itially present, was observed in several instances but was at best small compared to other changes in the nitroso compound.

When p^nitrosophenol was decomposed therm ally e r photoehemically in the presence of a nitro compound, i t responded in a manner which con* treated sharply with the behavior of the p-nitrosodimethylanillne. In the case of the phenol, the nitro compound exerted a decided inhibiting action upon such decomposition. This was studied in a variety of ways, v and while a complete end assured explanation of i t remains to be found,

eons light has been shed on It by the present work* Indications are

that the Inhibiting effect is not catalytic in nature, and that it is not to be ascribed to the absorption of ultra-violet radiations by the n itro compound. A p a r tia l and te n ta tiv e explanation of th is phenomena has been offered.

v i TABLE OF CONTENTS

Page PART I * OXIDATION OF NITROSO COMPOUNDS

INTRODUCTION - 1

REVIEW OF THE LITERATURE ------$

EXPERIMENTAL------10

TABLES I TO I H ------IS

FIGURES 1 TO S ------23

DISCUSSION OF RESULTS------27

SUMMARY------33

PART I I - DEVELOm.^T OF CHROMATOGRAPHIC AND SFECiROPHOaOMETRIC

METHODS FQt THE SEPARATION, IDENTIFICATION AND INTIMATION OF

SOME, NITRO, NITRGSQ ROD REUTjN COMPOUNDS

INTRODUCTION ------34

REVIEW OF LITERATURE - ~ ------~ ------38

sJCPPRIHONTAL ~ ------43

TABLES IV TO V I I I ------49

FIGURES 9 TO 1 5 ------61

DISCUSSION OF RESULTS------6 ?

SUMMARY ------70

PART I I I - INFLUENCES OF NITRO COMPOUNDS ON THE DECOMPOSITION OF

NITROSO COMPOUNDS

INTRODUCTION------71

EXPERIMENTAL------' ------79

v i i TABLE. OP CONTENTS continued

Pag®

TABLES IX TO XIX - - ~ ------83

FIGURES 16 MD 1 7 ------* - 90 DISCUSSION OF RESULTS ** ------9a

SUMMARY ------* . * ------99

BIBLIOGRAPHY ------* - . I jOO

APPENDIX following page - 109

Till LIST OP TABLES

Page PART I TABLE I Oxidation of p-nitrosophenol - --.-----•---18

TABLE I—A Oxidation of p-nitrosophenol ------20

TABIE II Oxidation of 2,4~dinitrosore«oircinal ------21 TABLE III Oxidation of p-nitros©dimethylani line------22

PART I I

TABIE IV Chromatographic Characteristics of the

Compounds Studied ------49

TABLE IV-A Standardization of Adsorbents - - - - — - - - - - 51

TABLE V Absorption D ata ------52

TABIE VI Sensitivity of Chromatographic Method ------58

TABIE VII Quantitative Recovery of Compounds ------59

TABIE VIII Analysis of Mixtures of the Compounds ------60

PART I I I

TABLE IX Reactions of N itro Compounds with

p-Nitrosodimethylianiline in Ordinary Light - - - - 85

TABLE X Reactions of Nitro Compounds with p-Nitroso-

dimethylaniline Ex osed to Ultra-Violet Light - - - 85

TABIE XI Reactions of Nitro Compounds with p»Mitrosophenol

in Ordinary Light - 8?

TABLE XII Reactions of Nitro Compounds with p-hitrosophenol

Exposed to Ultra-Violet Light - - - — - — - - - 88

i x LIST

Page

FIGURES 1 to 8* Oxidation of Nitro a a Compounds

to K itro Confounds - - — 23

FIGURES 9 to 12. Standard Beckman Curves------&L

FIGURES 16 to 17* Decomposition of p-Nitrosophenol - - - - - 90

x irocDumow - pa r t i

tm OXIDATION OF NITROSO COMPOUNDS TO THE CORRESPONDING NITRO COMPOUNDS

A sequence of reactions such ass X-H —*X-NO—>X-NG 2 appears at first glance to he a relatively ineffi­

cient way of synthesizing nitro compounds* Certainly this is true

in nest of those instances in whicn X-HQg may be prepared satis­

factorily by direct nitration* There are a number of special cases, however, in which synthesis via the nitroso compound offers certain

advantages, and a few in which i t may be th e only feasib le method*

For example, a specific nitrophenolic compound may be prepared in

this way with complete freedom from isomers and from polynitration

products, since the initial nitrosation is limited and specific*

There may be relative freedom from nuclear oxidation products if the

second step , the oxidation of th e n itro so compound, i s conducted in a carefully controlled manner* In some cases, the directing Influence

of the nitroso group may be utilised to secure, ultimately, particular

nitro compounds not readily available by other means* Fseudonitroles, and N-nitroso derivatives of secondary amines, are easily prepared by direct nitrosations; and oxidations of these offer routes to the

corresponding nitro compounds which compare favorably with alternative methods* A necessary part of such a process is, obviously, a method of

oxidising n itro so compounds to n itro compounds, in good y ie ld , with

the smallest possible manifestation of side reactions* The literature

contains accounts of a number of such oxidations; but practically

1 2

without exception, those are isolated examples. In some such reports,

details of procedure, operating conditions, and yields are meagre; in,

few if any of them does there appear to have been any systematic effort

to study the effects of variations in the conditions, or to determine

a s e t o f conditions y ield ing optimum re s u lts . In those e a rlie r papers in which the authors have described successful conversions of nitroso to nitro compounds, they have usually restricted their attention to the one or two substances with which they were immediately concerned, and have made no study of the possibility of using similar methods for the oxidation of nitroso compounds in general*

In choosing a reagent and a set of conditions, for an oxidation the following considerations should be kept in mind. The reagent must be strong enough to accomplish the desired result, it must be of such a nature that the reaction may be stopped at the desired stage, it should give the minimum amount of side reactions, aid the products of the oxidation must be seperable from the reaction mixture. There is as yet no scientific classification of oxidising agents. They are spoken of as "strong" or "weak 0 but these tsras have no exact meaning since the reagent that may be more powerful for one type of reaction may be less powerful for another type. The broad object of the present work was to commence a more systematic and integrated study of the oxidation of nitroso compounds in general to the corresponding nitro compounds. More specifically, the greater part of it was devoted to an investigation of the use of hydrogen peroxide as in oxidant for this purpose, Earlier workers had used i t w ith varying success on a few n itro so compounds. Hydrogen peroxide has several advantages as an oxidizing agent, Some of these 3 are that it is an efficient oxidising agent, it is soluble in a number of solvents, and does not add any by-product® to the system. In addition, its effectiveness can be varied widely by the choice of solvent, concen­ tration, catalysis, etc* In the present workj, the effects of altering a number of variable factors, such as time, temperature, and concentration in such oxidations were studied* The nitroso compound which received the most attention in this respect was p-nitrosophenol, but some work was done on other nitroso compounds in order to ascertain whether the oxidant was equally suitable for them, and whether optimum conditions for the oxida­ tion of various nitroso compounds would be approximately the same, or would differ sharply with different nitroso types.

In addition to hydrogen peroxide, a brief study was made of the oxidation of a few nitroso compounds, using other oxidants. Among those used were nitric acid, potassium ferricyanide, chromic acid and potassium permanganate* From the results obtained hydrogen peroxide appears to be a relatively good oxidising agent for the oxidation of the sodium salts of phenolic compounds in acqueous solution.

In order to facilitate the investigation of these reactions, it was necessary to develop methods for the separation, identification and quantitative estimation of the components of the reaction mixtures*

Chromatography seemed to be the best method for peiforming the separations, and spectrophotometry the best method for the quantitative estimation of the amounts of each component p resent. Due to the sim ilar s o lu b ilitie s of analogous riitro and nitroso compounds, the impossibility of distilling most of them, and the instability of some more common methods of separation were impractical. This method was also advantageous in that it made possible the use of low concentrations. Chromatographic and spectropnoto-

3 4 metric data v ro useful also in the identification of sm li amounts of by* products of the react ions* aa© and azoxy confounds for example,

Bart IX of this thesis, and the reprint attached as an Appendix, describe the chromatographic and spe ctrophotometrie characteristics of the nitro and nitroso compounds involved in the present work, of others whose future study is contemplated f and of some compounds of other types which appear to be potential by-products of the reactions studied* REVIEW OF THE LITERATURE - PART I

One of the earliest articles describing the oxidation of uitroso

compounds was that of Baeyer and Caro (4) who in 1874 reported the oxi­

dation of p-nitrosophenol to “iaonitrophenol11 with cold concentrated nitric acid.

During the following few years, a series of articles appeared

describing investigations of the possibility of using nitric acid as the

oxidant for this conversion. Polyiy r oxy-nit,roso compound® commanded the

major share of the attentions of these early investigators. The intro**

ductory article in this series was contributed by Baeyer (3) • Other

articles were presented by Schraube (53)* FuchB (25)# and Fitz (23).

Fuchs (25) oxidized l-nitroso-V*naphthol with cold concentrated nitric acid, and also with dilute nitric acid in acetic acid,. However,

he found that oxidation was accompanied by nit raid, on in both instances,

Oxiaation alone occurred when the nitroso compound was treated with

potassium ferricyanide in hot potassium hydroxide solution.

Fitz (23) attempted to oxidize 2,4^initrosoresorcinol with dilute

nitric acid, but even at low temperatures nitration accompanied oxidation, ' giving him 2, 4, 6-trinitroeoresorcinol. He was also unsuccessful in his

attempts to use potassium permanganate and potassium ferricyanide as

oxidants, excessive oxidation occuring.

Schraube (55) oxidized p-nitrosodimetlriylsniline with potassium permanganate and potassium ferricyanide, reporting best results with the

forner. They also used dilute nitric acid, but found that this resulted in oxiaation accompanied by nitration.

Avonheim (2) in the oxidation ofa mononiirosoresorcinol ether 5 6 found that both nitration and oxidation occurred whan using nitric acid,

Benedikt ( 8) demonstrated that nitric acid could be a suitable oxidizing agent for some nitroso compounds not susceptible to nitration* He oxidized trinltrosephloroglueinol to trinitrophloroglucinol by use of a mixture of nitric acid and sulfuric acid at roots ten^erature, Schiff ( 53) oxidized nitroaothyaol to nitrothyaol with potassium, ferricyanide in warn acqueoue alkaline solution. Using concentrated nitric acid, he obtained a dinitro product.

Probably the first investigators to obtain oxidation exclusively, with nitric acid, working with a nitroso compound susceptible to nitration, were Stenhouae and Groves (5$), Under rather mild conditions, they converted dinitroso-orcinol to dini tro~orcinol with dilute nitric acid at room temper­ ature, Use of concentrated nitric acid and heat, on the other hand, gave trinitro-orcinol as the principle product, Kostanecki ( 3 8) reported the oxidation of dinitrosocresorcinol to dinitrocresorcinol with nitric acid.

The only position open to further substitution here, however, would not likely be attacked by a cationoid group,

Stenhouae and Groves (59) were also successful in converting

1 -n itro s o- 2-naphthol to l-nitro~ 2~naphthol with nitric acid, and with very little additional nitration. They treated an acqueous suspension of the nitroso compound with the nitric add, A similar method was used by

Grandmougin and Michel (28) to convert 2-nitroso-L~naphthol and 4-nitroso-

1 -naphthol to the corresponding nitro compounds with nitric acid, with yields up to sixty percent.

In 1888 Konatanecki and Feinstein made a limited study of the effects of varying concentrations end temperatures on the oxidation of dlnitroso res orcinol with n itr ic acid, Benedikt and Hubl (9) converted the same 7

substance to the dinltro compound by suspending i t in ether and passing

"Mitroue acid vapors" through the suspension*

In later years* occasional papers have reported improvements in

technique or extensions of the method to other nitroso compounds. Bamberger

and Hubner (7) oxidised 2-nitronitrosobenzene to the dlnitro compound with

nitric add at 90-95°# obtaining 65$ yield. Michaelis and Kotelaann ( 4 8)

converted l-phenyl- 5Haethyl- 4-ni tros o- 3-py razole to the corresponding nitro

compound by warming in glacial acetic acid solution with concentrated nitric acid. Gilbert, Laxton and Prideaux (27) and Borsche and Fesks (13)

oxidised 2, 4-dinitrosoresorcinol with concentrated nitric acid at 0° C. to

the d in ltro compound. Bogoslovskii and Manutov (U ) described the oxi­

dation of p-nitros ophenol to p-nitrophenol with nitric acid. They reported yields of approximately 90$.

Reactions of aliphatic nitroso compounds appear less frequently.

Oxidations of pseudonitroles were described by Meyer and Lecher (44) (47)#

They used chromic acid in glacial acetic add to oxidize 2-nitro-2-nitroso-

propane and 2-nitroso-2-nitrobutane. A more recent description of the

oxidation of aliphatic nitroso compounds was contained in a paper by Piloty

and Steinb&ck (52). Schmidt, J. and Widmann (54) used several different oxidising agents for the oxidation of the diethyl ester of nitroeosuccinlc

acid to the corresponding nitro compounds. Best results were obtained using 10$ HgOg in dilute sulfuric acid. The possibility of the elimination of a nitroso group in the side chain of an aromatic molecule, by oxidation under mild conditions was described by G abriel and Meyer (26). They oxidized o-nitro-nitroscanethyU benzene to O-nitrobenzaldehyde with several oxidizing agents.

The utilisation of the oxidizing power of nitrous acid to convert nitroso compounds into nitro compounds has been reported. Previously cited

articles by Schiff (33) and Benedickt and Hubl (9) contain examples of

such study* Haeussermaan and Bauer (30) described their treatment of

tertiary amines with nitrous acid, reporting formation of mononitro deri­

vatives. This might well represent nitrosation followed by oxidation. The

same possibility exists in the ease of the conversion of dimethyl-p-toluidine

to 3 -nitro dimethyl-p-toluidine by the action of nitrous acid, as reported

by Hodgson and Kershaw (33)*

Oxidation of K-nitroao compounds accompanied by rearrangement re*

suiting in the formation of C-nitroso products are reactions of considerable

in te r e s t ; examples of them were described in papers by Stoenaer ( 6 0 ); and by Busch and co-workers (14) (15)* Around the turn of the centuiy, several investigators studied the

effects of a number of different oxidising agents under controlled condi­

tions. Frledlander (24) oxidized 5-nitro and 8-nitro~ 4^nitroso-l-riaphthols to the corresponding dinitro confounds by treatment with warm, alkaline

solutions of potassium ferricyanide. Borsche and Berkhout (12) boiled

the sodium salt of 4 -nitrosoresoreinol with a dilute solution of hydrogen

peroxide in dilute alkaline solution. They obtained the corresponding n itro compound in about IQfjL y ie ld . Beyewetz and Foizat ( 36 ) explored the

possibility of oxidizing an assortment of nitroso compounds with ammonium

persulfate under varying conditions. In general, they obtained excessive

oxidation, indicating that ammonium persulfate is a poor oxidant for this

type of reaction. Kuhn and von Klaveren (40) advocated the use of a mixture of nitric

acid and hydrogen peroxide as a general method for the conversion of nitroso

compounds in to n itro compounds. Using th is method with a number of n itro - 9 nitroso compounds they succeeded in obtaining yields of 62 - 88% of the dinitro

products*

Hodgson and co-workers ( 3 3 ) (3 4 ) made a study of the nitrosation

of a variety of phenolic compounds and some of their papers included descrip­

tions of the conversion of the nitrosation products to nitre compounds*

In a majority of the papers Just cited* details of procedure* condi­

tions* and yields were incomplete* and comparative studies of the effects of

changing conditions were almost entirely missing* In fact most of the early

investigators exhibited a tendency to omit the conditions of reaction* yields*

and by-products obtained entirely* FART I - MXmwmM,

U ). Materials &***& The following materials were obtained from the lastman Kodak

Research Laboratory* The sodium salt of ^niiroeophenoL, 2-irKiinltroao- resoreinol, Inaltros o- 2-naphthoi, 2-nltros Q~l~aaphthol* and pnaitroso- dime thylaniline. The latter was purified by recast alii sation from ether and petroleum ether* The melting point was 85-36° which agreed with the Talus given in the literature*

The faydrogen peroxide used was Merck*a Superoxol (30%). The actual concentration of this solution w as determined fcy titration against sodia thiosulfate tfcioh in turn had been standardised against potassium diehrornate. The procedure used for this determination was the

Kiagselt method found in Scott *8 Standard Analysis Vol. page 2081. (B). Proe.dure tor Um R a t i o n Mtgfcuraa.

The solutions which were used in the reactions were made up of known concentrations with respect to the nitroso compound and the oxidant.

At the end of a specified time intervalf an aliquot (usually 5 ec*) of the acqueoua solution was pipetted into a 50 ce« erlenmsyer flask which was cooled in an ice water bath* This solution was acidified with d ilu te hydrochloric a cid , and ex tracted w ith eth er and then w ith benaeme.

The extracts were made up to volume with benssas, This solution was then subjected to the chromatographic and a pSc$fcb$&ot ometric method of analysis described in detail in the attached appendix, and the amount of nitro compound paresent calculated. The experimental error involved in this type of procedure has been calculated to be approximately 3%. (c). lim oxidation of aeqmoua solutions of the sodium a alt o f

10 11

PHiitroaophenol with hydrogen peroxide*

A solution of 0*1 M sodium salt of p-nitrosophenol was mads

up and used as the standard solution for these runs* The reaction

solutions themselves were made up by diluting 50 cc* of the standard

p-nitrosophenol solution to 100 cc* with the proper amounts of

distilled water and hydrogen peroxide* These solutions were allowed

to stand at a certain temperature and at the end of time intervals,

samples of the solutions were withdrawn and analyzed* The results

obtained in this series of reactions are tabulated in Tables 1 and I-A,

and are represented graphically in Figs* 1, 2, 3, 4, 5 and 6 *

For the quantitative determinations, samples of the benzene

solution (generally 3 cc*) were chromatographed on #2 columns* Aliquots

of the benzene solutions were also chromatographed on # 1 columns, and

streaked with various reagents to determine the positions and nature

of the zones present* It was observed that in the runs at room temperature, three zones were obtained on the columns soon after the

reaction began* They were from the top (l) a yellowish zone which gave a pink color when streaked with sodium hydroxide, which was not identified ( 2 ) a zone identified as p-nitros ophenol and ( 3 ) a zone identified as p-nitrophenol* As the reaction proceeded the p-*iitro—

sophenol zone decreased and disappeared* The top zone increased in intensity at first and then began to decrease slowly after the p-nitroso- phenol zone had disappeared, finally disappearing entirely*

In Table I-A, the results of two runs which were made under identical conditions insofar as it was possible to do so, are given in order to indicate the extent to which the results were reproducible*

There was always some variation in individual runs* Most of the data la

in this portion of the thesis represent averages, or approximate

averages, of the results obtained in mors than one experiment.

It should be pointed out that the data in the tables show in each case th e conversion of n itro so compound to n itro compound, expressed in terms of percentages of nitroso compound originally presen t.

The oxidation of p-nitrosophenol at boiling temperatures, patterned after the method of Borehe and Berkhout (12) was also in­ vestigated for comparison. A solution was made up containing SO cc. of the 0.1 N sodium salt of p-nitros ophenol, 40 cc. of 1$ sodium hydroxide, and 1 0 cc. of 15$ hydrogen peroxide, and refluxed for 1 hour.

A yield of 16$ of the nitrephenol was obtained. On making up the re­ action solution a vigorous evoluticn of gas commenced before the reflux- ing began possibly due to the presence of the alkali. The above run was repeated using 50 cc. o f 0 .1 N sodium salt of p-nitrosophenol so lu tio n , 50 cc. of water and 1 0 cc. of the same hydrogen peroxide solution. After refluxlng for 1 hour, the solution was cooled and the n itro compound determined as before. The y ie ld of the n itro compound obtained was 30$ . (D). Oxidation ot 2 .it-dinltro»or«»orclnol with hydrogen peroxide. A 0.1M solution of the sodim salt of 2,4-dinitroresorcinol was used as the standard solution in making up the reaction mixtures fo r these runs. The reactio n so lutions themselves were made up by d ilu t­ ing 50 cc. of the standard 2 , 4~ d in itro 0 ores orcinol solution to 100 cc. with the proper amounts of distilled water and hydrogen peroxide. The reactions were run as described above, and the results are tabulated in

Table II, and are represented graphically in Fig. 7. 13

A 0*05 M solution of the sodium salt of 2#4-41aitK>sorosareiuol containing hydrogen peroxide was allowed to stand for 24 hours at room temperature (approximately 3 Q°C). A y ie ld o f 65$ of th e n itro expound was obtained*

By fellcwing for comparison, the method of Borsehe and Berkhout

(1 2 ) using 50 cc* of 0*05 M solution of 2 , 4 -dinit roeoresorcinol, 10 oo* of hydrogen peroxide ( 1 $S) and 40 cc. of water and refluxing for 2 hours, a yield of 25% of the n itro compound was obtained*

<*>• Q*U»tt«n * f B-nittna»

A 0*1 M solution of jHoitrosodittethylaniline in acetone was used as the standard solution for making up the reaction mixtures*

These were formed by diluting 50 cc* of the standard solution to 100 cc* with the proper amounts of acetone and hydrogen peroxide* At the end of specified time intervals* small aliquots of the reaction mixture were withdrawn and diluted up to volume with benxene. These solutions were chromatographed and the nitro compound determined quantitatively* The results of these zuns are summarised In Table H I, and are shown graphically in Pig* 3.

Sehraube ( 55) had described the oxidation of the p-nitroao- dlmethylaniline hydrochloride with potassium permanganate, reporting

"good" yields but not mentioning any quantities or conditions. In order to eeupare the relative merits of this method with the one just described, a run was made i n the following manners A 0*05 H so lu tio n o f the HCl salt of p-nitrosodiaathylaniline was treated with an excess of 0*05 H potassium permanganate, with slight warming* The permanganate solution was added slowly with stirring to the nitroso solution, after which the entire mixture was allowed to stand at room temperature for 24 hours*

A small aliquot of this solution was evaporated mid the residue extracted 14 with warm hamsm* Using the chromatographic and spectrophotometric method of analysis, the yield of nitre compound was found to be £0#*

(F). QnldaUan of l-nitro>o-2-nariittol and 2-nitroao-X-napfathol.

the oxidation of the sodium salts of these two imphthols with hydrogen peroxide was accomplished with good yields* Using a procedure atoll iar to that used in the study of the oxidation of the sodium salt of p-nitros ophenol, a number of runs were made in an effort to deteralne the optima conditions* Best results were obtained as follows*

A 0*05 K solution of the sodium salt of 1-nit roe o-«2-nap hthol was allowed to steed for 24 hours at room temperature in contact with a

3M salutlo^ of hydrogen peroxide* The conversion to the nitre compound wider these conditions wee calculated to be On repeating the above reaction and using 2-nitroso-l-naphthol under the same conditions a yield of 6G£ of tie nitre compound was obtained on standing for 43 hours*

(6). Ctodation of 2-MltW)8 0-a-nltropyonane (mwarl pawtdonltrole)

The 2-n itro s 0- 2-nitropropane used in this series of runs was prepared by the method of ifygaard (50) who nitrosated 2-nitropropei» with nitrous acid* Meyer and tosher (44) reported a yield of 7C$ of the dinitrepropane on treating an acetic acid solution of the nitroso compound with chromic a c id , and warming* Several a t t e s t s were made in the present work to duplicate their results using this procedure! however* yields of about 50t were the best which could be obtained* A group of exploratory runs were made* using 5 gram samples of the nitroso compound and varying the conditions of the reaction, in an effort to determine those conditions which would give the optimum yield* The following procedure was found to give the best results* and was performed twice* using 25 gram sample* o f th e n itroso compound. The yield s of the d in itro compound obtained were 85 end S@$* H

0 3 ** 3 ® a 1 & §• 3 «*■* U •8 ■3 xs «* +» ■§ 1 « 3 a i S * a I I1 ^ « © © a ^ 1 3 i 3 Mill u o 8 Ti I i 8 I I I * 2 9 © 1 ft r s• i -+3J3 *1 0 3 <8 35 •« <3 *g I 1 ■3 t>8 <8 1 S. & 9 I I ■g g 3 O 3 JB I ! s 4> H V4 IS © SO I 1 S 8> 1 I© f * oi 1 O I 4»£ 16

(2) Oxidations idtli glacial acetic acid as the solvent, and with tes^eraturee above 25°. The oxidation with hydrogen peroxide in acetic add was strongly exothermic, making i t difficult to control the temperature of the solution* The beet results in this series of reactions were obtained at a temperature of 45° using a dilute solution of the nitroso confound, and gradually adding sufficient hydrogen peroxide to make the concentration of the oxidant 6$* On standing for 3 hours a yield of approximately 10$ of the nitre compound was obtained* Very little nitroso compound remained in the reaction product of any run in this group* The s olution, which was blue at the beginning of the reaction, gradually became colorless, and then after a considerable period o f tie s became brown. At b e st, these reactions showed that oxidations wader these conditions, above room temperature, did not appear promising,

(3) Cbddations with glacial acetic add as solvent, at temperatures between 0° and 1& varying the times of exposure, and the concentrations of the reactants. On adding hydrogen peroxide to a dilute solution of

2Hoitrose-2-nitroprepaxie at 15° and allowing the solution to stand for

24 hours at this temperature a yield of about 15$ of the nitre compound was obtained* The solution had changed in color to a lighter blue and s till contained a considerable portion of the original nitroso compound.

Repeating the reaction at lower temperatures, led to obtaining lower yields, for the same period of time. The maximum yield of this series of reactions was obtained by dissolving 5 grams of 2*#iitroa0~2~ nitropropane in 60 ec, of acetic acid and gradually adding 20 cc* of

30$ hydrogen peroxide with stirring* The temperature was maintained at about 15° during the period of mixing and the period of reaction* At the end of a three day period a yield of 40$ of the nltro compound 17 was obtained* Using larger excesses of oxidant, higher concentrations of reagents, and longer tins gave reduced yields.

(H) * Miscellaneous Oxidations*

Kuhn and eon Klaveren (10) reported the oxidation of some nitroso compounds such as l,2-dimethyl-4~nitroso-5**nitrobenfcene with a mixture of hydrogen peroxide and nitric acid in acetic acid* fen grams of the nitroso compound were dissolved in 150 cc* of 30$ hydrogen peroxide and finally treated with 10 cc* of nitric acid (density 1*40).

This solution was warmed on the steam bath until the solution changed from a dark green to orange* Then, excess water was added and the dinitro compound precipitated* Following the above procedure and using 2,4- d in itro ao reso rcin o l and p-nitrosophenol as the n itro so compounds, yields of the nitro compound were 40 to 30$ respectively*

Fuchs (25) used a hot alkaline solution of potassium ferricyanide to oxidize some nitroso naphthoic to the corresponding nitro compounds*

Two grams of the nitroso compound were dissolved in 750 cc* of dilute &0H and the hot solution treated with 50 grams of potassium ferricyanide*

The red so lu tio n became yellow on standing on the water bath with heating*

Using l-nitroso-2-naphthol, 2,4-dinitrosoresorcinol and p-nitroaophenol as the nitroso compounds and following the above procedure, yields of the nitro compound obtained were 55, 40 and 45$ respectively*

The results obtained in the above reactions were the results of a few preliminary runs* This group of experiments was not carried far enough to determine the exact conditions necessary to obtain the maximum yield of the corresponding nitro compound* TABLE I

OXIDATION Of P*HITROSOPHEMQL TO P-NITRQPHENOL WITH HJDRQGEB PEROXIDE OF DIFFERENT CONCENTRATIONS FOB DIFFERENT LENGTHS OF TUG. RESULTS EXPRESSED IN PERCENTAGE OF ORIGINAL P«NITfiOSC*»KENQL CONVERTED TO P-NIIECPHENQL. THE TEMPERATURE FOR THESE RUNS WAS 38°

TIME Em 1 RUN n mm i mu n aim v aim VI HUM 711 0.22 0*4* 0.691 1.62 3.22 42 iig02 %°2 h °2 %o2 V fe •A

6 h rs. 84.5

8 bra* 47 71 90

12 hr®. 43 7®

16 hr®. 77 90 i

2 days 14.7 40.5 64.5 78 2& days 86 86

3 days 16.5 83

4 days 51 66 85 88 83

7 days 20.6 53 64.5 81 83 79

10 days 20 53 64 80 69 12 days 20 49 61.5 80 ?6 i t

0£

z i i s n

t0 98 t t IS 6 69 91 Zl 18 8 H 6'Z9 6 i$ 9 69 69 9 69 9 99 6’€9 € £9 €

zo*n zoh %V* J99*t mm *rc »*T SHfiOH ix mu X SOI si mil XI HflH mA mm i a m

*0O9 SVM IX ON? X SSftH 3DJ m iTO»x sw* n ®ir xiia sms «>j sm m jm "tohssj -ohixim ox mlmmo tom josotoim imoxso m wmmm& s i o s s m a x i $irmtm *fm jd shiosst xhsmjjig so j ssDtirasaDHDO M m i i o jo ymoMd mmmm um xosaHjososixsNi m murmrn

m m m o * t m m i TABLE I - A

OXIDATION OF P~NITRQ30PHEN0L WITH HXDROGEN PEROXIDE IN ACQUEOUS SOLUTION AT 2 8 ° . TWO BUMS WEEK NUDE UNDER EXACIU THE SANE CONDITIONS* RESULTS EXPRESSED IN PERCENTAGE CF ORIGINAL P-N im G SG - PHENOL CONVERTED TO P^ITROPHEJJGL. RUN VI IS ALSO TABULATED IN TABLE I .

TIKE RUN V I RUN I I I

6 h rs . 63

8 h rs. 71

12 h rs. 84

16 bora* 90

1 day 87.5 88.5 l£ days 84

2| days 66 81

4 days 83 79

7 days 79

10 days 69 72

20 TABLE IX

o x i d a t i o n o f t h e scorn s a l t o f 2 , 4-DmmosaiascRciHGi. t o t h e CORRESPONDING NITRO COMPOUND KITH HXDROG&K PEROXIDE CF DIFFERENT CONCENTRATIONS FOR DIFFERENT LENGTHS OF TIME, RESULTS EXPRESSED IN PERCENTAGES CP ORIGINAL 2,L^>I»IXROSORESCKCINOL CONVERTED TO 2,4-OINITRCRESCaciNOL.

THE IK RISK X TimE IK RUM XX RUM XIX HOURS TEMP* 1.6* TEMP. DAIS 1.5* 3* V z ¥ > 2

12 30° 60* 37*C. 1 53

24 30° 72.3* 37°0. 2 48 39

36 30 76* 37°G. 3 40 31

48 30° 6 # 37°C. 4 26

60 30° 67* 37°C. 5 29.5

21 TABLE III

THE OXIDATION OF P-NIXROSCOIMETHILANILINE TO F-NITRCDIMETHILANILINE WITH HTDROGEN P l ROXIDE OF DIFKEKENT CONCENTRATIONS FOB DIFFERENT ISNGTHS OF TIME. RESULTS EXPRESSED IN PERCENTAGES OF ORIGINAL P-NITEOSCSIMETHILANILINE CONVERTED TO P-NITRODIMETUILANILIUE.

TIKE XU JttJM X HUS XX TIME IN RUN . DAIS TEMP, 356 DAIS MP# 5* V fe «2°2 *2°2

X 32° 3 12 1 37°C. 20

2 32° 4 14 2 37°C. 20

3 32? 5 3 37*0. 36

4 32° 5,5 as

5 32° 6 38

7 32° 10 46

9 32° 53 11 32° IS

12 32° 20

22 °/c /Vs^ro °/0 jy) fro Com pound S0\ 60 0 9 70 70 Tm i c/ny$ in "Time ¥ 6 & Ron E27 Tnblel Ron ST Th6/es ZnncfJT Th6/es Ron ST R n u D n/ R I Tnt/e AndYD Run SO — / F/G £ Rons YLVnndJi Rons £ F/G Time inTime Moors o s 2 StS 20 is /o

T*t ! >!« X w -* - /O

F'tGf RUMS 1 ,2 1 , fin d M TRBIS2 70

TfME /M&fiVf

F/G 2 nutiS W fin dC 2 T 88L E I

0 8 0'

6 0

3 0

TtM8 //V o * y s & " R uns X and XL T#b/& I

§ 1 “ 90

0

7&

s 70- \. 2X —H

*J 7 - Runs 2,22 Grid III Th6/&21 BO

m

M

”Tsme m Pnys 09

jrpu v (s 'j- s-uny Part X - Discussion of Results

The first group of experiments consisted of treating acqueous solutions of the sodium salt of p**nitros ophenol with hydrogen per cad do at concentrations ranging from 0,2# to 4$, at constant temperature, and determining the amount of nitro compound present in the solution at the end of varying periods of time. These results are tabulated in Tables £ and I-A> and represented graphically in Figs, 1, 2, 3# 4* 5, 6,

The results obtained from these experiments indicate that it is possible to obtain nearly quantitative yields of p-nitrophenol, by proper control of the conditions of the reaction* It was observed that there was a certain time for each concentration of peroxide at each tem perature a t which the optimum y ie ld o f th e n itro compound was produced; longer periods of exposure diminishing the amount of nitro compound obtained*

At very low concentrations of hydrogen peroxide, the oxidation of the nitroeophenol appears to be roughly proportional to the concentration of the hydrogen peroxide* As might be expected from a consideration of the properties of the oxidant and the method of performing the reaction, the results were q u a n tita tiv e ly reproducible to an approximate degree only* However, the same general type of curve was obtained for each of the runs, and the results were reproducible in a qualitative sense*

As the reaction proceeded, the amount of nitro compound in the reaction mixture Increased to a maximum value, after *foich i t began to decrease on standing for longer periods of time* As the concentration of the oxidant or the temperature or both, was increased, the nitro compound reached a maximum concentration in a shorter period of time, and the

2 7 2S decrease in the amount of nitro compound on further standing became g re a te r.

Prelim inary runs were made a t the beginning of th is work in which higher concentrations of hydrogen peroxide were used* Although difficulties in analysis were encountered, the results indicated that the time required to attain a maximum yield was progressively decreased as the c concentration of the peroxide was increased, and the nitro compound diminished to a greater extent and at a faster rate upon standing after the maximum yield had been achieved* These reactions were not studied thoroughly under such conditions.

There are two possible explanations for the decrease in yield of jwxitrophenol when the optimum time was exceeded* One is that nuclear oxidation o f the nitro compound takes place, is long as nitro b o - phenol is present in the system, the hydrogen peroxide is used up in the oxidation of this compound to the nitro compound. Alter the nitroso compound which is easily oxidized has been used up, the excess hydrogen peroxide begins t o act on t he nitro compound.

This phenomenon night also be explained in the following manners

The determining factor in oxidatloxweduction reactions is the ratio of the concentrations of the oxidized and reduced forms of the particular constituents, fbr the general reaction

Gxid / n e —*

Feigl (22) has offered the theory that hydrogen peroxide may be represented in the tautomeric formas o- /✓ r /vN O’' #. 4k u '0 * 0 Cn ( 2 ) of which (1) would set as m oxidizing agent and (2) as a reducing agent. 29

New at the beginning of the reaction we have a large concentration of a n itro so compound t&ich is e a sily eaddlcsd* ami m excess of hydrogen peroxide which has a large tendency to act as an oxidising agent *

Therefore, there would be a large potential ceasing the reaction iWf « 0 / i^Og^BNOg/ ii^O to proceed fro* left to rl^ii*

As the reaction proceeds the nitroso compound is converted into the nitro compound until i t is completely need up* At this point* we would have excess hydrogen peroxide and the maximum amount at nitro compound present in the system* Since the oxidation potential of the nitro compound increases as its concentration increases* end the oxidation potential of the hydrogen peroxide has decreased* it sight be possible for the excess hydrogen peroxide to act as a reducing agent m d the nitro oompeund to act as an oxidising agent* In any system* the completeness of an eoddatioxv* redaction system will be dependent upon the difference between the single potentials between the two reacting oxidation-reduction systems* It is probable that one of the above or perhaps a combination of both explains the decrease in concentration of the nitro coopmmd on standing with excess hydrogen peroxide* Experimental eridmce was not obtained which would substantiate or eliminate either of the above explanations* Should the nitro compound be reduced* i t is possible that p-hydroxyphei^lhydroxylaiaine or p-amino- pbendl would be formed* Attempts to prepare the foromr were not successful* However* if this compound were in the reaction mixture* it should give a separate cone on the column which could be detected with sodium hydroxide as the streaking reagent* and such a cone was not detected*

Neither wan p-aainophenol detected as one of tbs components of the reaction product* Oxidation at the boiling points of the solution, employing hydrogen peroxide as the oxidant as described by Borsche and Berkhout (12) were tried for the sake of comparison, using the sodium salts of p-nitroso- phenol and 2,4-dlnitrosoresorcinol as the nitroso compounds* the yields obtained sere smaller, than in those cases where lower temperatures were used* It was found that by decreasing the concentration of alkali employed by these investigators, the yields could be increased* It might well be that by varying the concentration of the oxidant, and the time of exposure s till higher yields could be obtained using their method* On adding the oxidant and heating, it was noted that a vigorous evolution of gas took place, indicating that perhaps a great deal of the oxidising potential of the peroxide was lost through the formation of molecular oxygen*

Experiments were also made employing the sodium salts of 2,4-* dinitrosoresorcinol, 1-nit roao-2-napht hoi, and 2-nitros o-l-napht hoi as starting materials, and hydrogen peroxide as the oxidant* A complete study of these compounds was not made; however, the re s u lts obtained indicated a general sim iliarlty between their behavior with hydrogen peroxide, and that of p-nitroeophenol• Yields matching the best yields obtained with the nitrosophenol were not realised, but there is not sufficient reason to conclude that such yields could not be achieved by using the same general method under appropriately modified conditions*

The yields obtained on oxidising solutions of p-nitros odiiaethyl- aniline in acetone with hydrogen peroxide were fairly high, although the time required to reach a maximum yield was much longer than in the case of the oxidation of the acqueoue solutions of the sodium s a lts of the phenolic compounds. liaising the tem perature in an ii ff BQ> tO vn 6 3 *% & * K « 5- 3 « tff § i1 $ ft I1 & SE - I 6 S 1 I 'i ni *r | a % I i h » er $ I I& i II S' i S>ft* H) o 1 I 3 c* ? I£ sr(0 I ii f"~ r II a «

I w$n non®*** f>«*vraa UDT*^

The oxidation of six nitroso (five aromatic and one aliphatic)

compound® with hydrogen peroxide to the corresponding nitro compounds was studied* The reactions were run under different conditions to

determine those which would produce optimum yields* The comparative

effectiveness of several other oxidants was studied more briefly.

Hydrogen peroxide was found to be an efficient oxidising agent

fear the oxidation of aromatic phenolic compounds, and fo r the one

aromatic amine studied* The effects of temperature, time, and

concentration on the oxidation of the sodium salt of p-nitrosophenol

using hydrogen peroxide as the oxidising agent was studied In semis

d e ta il. A siailiar study of the oxidation of 2-nitro-2-nitrosopropane

with hydrogen peroxide showed this oxidant to be inferior to chromic

acid for the preparation of 2,2-dinitropropane*

33 PART I I - I&TRGOUCTXOH

Chromatography Is that branch of analytical chemistry which deals with the separation of compounds by taking advantage ©f differences in their adsorption affinities, these differences are due, at least in part, to the functional groups attached to the molecule®, the sizes of the molecules, the molecular configurations, and the solvent effects during the development. In previous years, much work has been done by various investigators in order to obtain data from which empirical formulas could be derived which would make it possible to calculate the rate of zone movement of organic molecules cm a column of adsorbent.

Although this technique is now widely used in chemistry, it is still a® much an a r t as a science, to solve a given problem, the investigator

■net still rely upon trial and error, intuition, or the previous work of others to a great extent.

Under favorable conditions, when two or more substances are d is­ solved in the proper solvent, put on a column of adsorbent, and washed down the column with the proper developer, they will separate Into zones because of the differing degrees to which they are adsorbed. If the compounds are colored, the sones may be ascertained visually; if they are colorless, the positions of the zones may be located by extruding the column and streaking it with a reagent which will react with the adsorbed compounds to give colored zones. From the position of the zone, the "R” value (or rati© of rate of flow of the zone to rate of flow of the solvent on the adsorbed column) may be determined.

The pure compound may be recovered from a zone by eluting or washing the zone off a column with a solvent which is more strongly adsorbed than the compound itself. On evaporation of the eluting solvent the pure

34 35 compound w ill remain* By varying the adsorbent, solvent, and developer used, i t i s possible to separate almost any combination of compounds,

Including isomers of nearly Identical structures* The above technique for the separation and purification of mixtures of substances, is be­ coming increasingly important in analytical chemistry*

Spectrophotometry as an analytical procedure for the identification and quantitative estimation of compounds in solution is also an important analytical tool* This branch of analytical chemistry deals with the measurement of the relative amounts of radiant energy absorbed by a solution as a function of the wave length (or frequency) of the radiant energy* The absorption curve obtained by plotting the absorption against the wave length of a substance in solution is characteristic of the substance in that solvent; and the extent of absorption at any wave length (preferably one at which maxi mum absorption occurs) is proportional to the concentration of the solution* It is generally considered that a compound may be identified by determining its melting point, its rate of flow down a column, and its light absorption curve*

Several workers (id) (29) (31) have used chromatography in con­ junction with spectrophotometry as a means of separation and estimation of the components of mixtures* These techniques are particularly use­ ful in the separation and estimation of small amounts of closely related compounds from mixtures* In the present work, it was necessary to develop chromatographic and spectrophotometrlc methods suitable for separation, identification, and estim ation of n itro compounds, nitroso compounds and some related compounds, from solutions containing various mixtures of them* The commonest mixture contained a n itro so compound and i t s n itro analogue* 3 6

Such pairs are usually hard to separata by other methods, since they may resemble each other closely in s o lu b ilitie s , and tend to decompose upon attempted distillation*

Earlier work by the same author (see the attached publication,

Appendix I) developed chromatographic and spectrophotometrie methods for such analytical determinations of 13 nitro and nitroso compounds, includ­ ing 6 analogous pairs. The present work is a continuation of this earlier work and has been expanded to contain similar data on some azoxy, and amino compounds. Twenty-four additional compounds are reported in the present thesis.

It may be observed that while these data were obtained primarily to facilitate the work described in Parts I and III of the present thesis, they have some value of their own. They represent an extension of chromatographic and spectrophotometric knowledge which may be utilised for analytical purposes by any subsequent Investigator whose work in any field involves some of the 2k nitrogen compounds whose character­ istics are described here.

Several of the compounds used in this work were synthesized, using standard methods found in the literature} others were already available.

The chromatographic characteristics of the compounds were determined, and the conditions necessary for the separation of the components of mixtures of analogous compounds were worked out. The sensitivity of each one (its minimum concentration in solution necessary to give a z o n e which could be detected) was determined. Standard absorption curves were obtained for each of the compounds in absolute ethyl alcohol by use of the Beckman Model D. U. Ultraviolet Spectrophotometer. The accuracy of the method for the separation and quantitative estimation of the compounds studied was checked using solutions containing known q u a n titie s o f auch compounds, both sing ly and in a&xtures* In general, the range of error was found to be less than 3% of the actual concentra­ tion, in either direction# PART I I - m i i m OF THS LITERATURE

Chromatography was invented by a Russian scientist, Tswett (60), in 1906* He found that some of the various pigments in green leaves

could be isolated by adsorption. Freshly prepared petroleum ether ex­

tr a c ts of the leaves were put on a column of p recip itated chalk and

developed with the same solvent * Using this procedure, he was able to

separate various chlorophylls and xanthophyll* from plant®. It was from

this separation that chromatography received its name.

Wilson (66), Weiss (64), and De Vault (19) among others set forth mathematical theories which related zone formation to the adsorption

isotherm* They showed th a t the ra te of movement of a zone could be

calculated if the adsorption Isotherm was known.

The need fo r a method of standardising adsorbents was early re­

cognized. LeRosen (41) defined a function "ft" as the ratio of the rate

of flow of the adsorbed zone to the rate of flow of the developing

solvent, and described a method for the standardization in terms of

this ratio (the "H" value). The use of a standard compound, o-nitro-

a n ilin e , and of a term H* which expressed the ratio of the rate of

flow of an adserbate zone relative to the rate of flow of this compound

was suggested by LeRosen (42).

The rate of movement of a zone as a function of the concentration

and volume of the solution and the column position was studied by LeRosen

(43) using the system silicic acid, benzene and o-nitroaniline. Strain

(61) also made a study of the conditions which affect the adsorption of organic compounds on a column. He found that the sequence or order of

adsorption varied with the solvent, the adsorbent used, and vdth the

36 39 kinds of substances adsorbed* He pointed out that other factors such as the concentration and the temperature influenced adsorption. By alteration of these conditions, Strain showed that the sensitivity and applicability of the adsorption method for separations could be increased* so that sub­ stances which could not be separated under on® set of conditions might be separated adequately under another set of conditions. Strain offered, also, a good general description of chromatographic techniques (61) in­ eluding a description of the equipment used, and an account of the experimental procedure.

Chromatography was used by a number of authors fo r the p u rific atio n of small quantities of mixtures that were difficult to separate by fractional crystallisation. Winterstein and Schon (67) used this method to separate isomeric polycyclic aromatic hydrocarbons, after failing to separate these compounds by distillation or recrystailisation. Many similar applications have been described. Among others, White and Dryden

(65) studied the separation of aliphatic alcohols by the adsorption of their 3, 5-dinitrobensonates * They attempted to separate forty pairs of these derivatives; twenty-five pairs gave two distinctly-separated cones, eleven pairs gave one sone of varying composition, or overlapping of sones, and six pairs were completely inseparable. The twelve pairs of derivatives

i of compounds between methyl and hexyl alcohol were separated easily.

Coleman and Rees (17) separated the products of hydrolysis and alcoholysie of 5 or 6 methylated disaccharides# Their p-phenylaaobensyl derivatives were formed and separated by adsorption on silicic add.

Identification was obtained by measuring their respective specific rotations of monochromatic light. Cassidy (16) separated several fatty acids, (including lauric, 40 nyristie, palmitic, and stearic) from petroleum ether solution on a carbon

column, A relationship between the positions of the sones and the adsorp­ tion isotherms was hypothesised,

Kirchner and Prater (37) separated the carboxylic acids ttm acetic to capraic, inclusive, by the separation of their p-phenylphenacyl

esters. Silicic acid was used as the adsorbent and petroleum ether*

bensene mixtures as the solvent and developer, A uniform series of

separations was obtained, with the lower molecular weight compounds being the mere strongly adsorbed,

A method for the separation of aromatic derivatives from gasoline

by means of chromatography* using silica gel as the adsorbent, was developed

by lipkin, Hoffeoker, and Martin (44) • A similar method for removal of

acetic acid from gasoline using the same adsorbent was described by Jones

(35). Owens (51) gave a method for the quantitative determination of the

amounts of cosqsounds in a mixture by matching the optical densities of

solutions of compounds against & pure solvent. This method was known as

an internal method or null method. Comparison of the optical densities

at specified wave lengths of a standard solution of known concentration and one of unknown concentration of the same compound with respect to the pure solvent allowed the concentration of the latter to be calculated,

A method was worked out by Mark and Porsche (45) fo r the c a l­

culation of the concentrations of the constituents of a binary mixture

from the experimentally obtained absorption data, and the absorption

data for solutions of the pure constituents,

A method was put forth by Berthaaer, Jones and Metier (10) for

the determination of acetone in mixtures with diisopropyl ether, Isopropyl a alcohol and low molecular weight m m olefins, by measuring the optical density of the solution at various wave lengths*

Several authors have described the use of spectrophot ometry in conjunction with chromatography as a means of separation and quantitative estimation of snail quantities of confounds in mixtures* in interesting example was the method described by Davis and Ashdown (IS) for the de­ termination of the variation of the amount of diphenylamfn® in a smoke­ less powder during aging*

The quantities of Vitamin HAM in fish d ie were determined spectro- photoaetrically by Halpem (31) • He separated the components of the oil ehroaatographically* This method was used to determine the quality of the carrier oil also*

A apectrophotometric procedure for the quantitative estimation of

Vitamin "£* was se t fo rth by Defefitt and Sullivan (20). The Vitamin WD ” was separated from the Vitamin "A" by use o f a chromatographic column*

It was also separated from stereols and carotenoide* Much the same pro­ cedure was used fey Smith (57) for the estimation of gossypol in cotton­ seed o il* Gulletrum, Burchfield and Judy (29) described a method for the separation and estimation of small amounts of p-benzoquinorxe monca&me

(tautomerically equivalent to p-nitroaophenol) in mixtures containing p-bensoquinone dio-yime and the products of the side reactions which took place during the nitroeation and aximatlon of phenol* Their method mad* use ef chromatography as a means of separation, and of spectro­ photometry as a means o f estim ation o f th e amounts o f monojdUae and

present* The work described in this thesis is a continuation and enlarge­ ment of the work described, fey the present author in a previous paper* 42 paper, by Edwards and Tate (21), described procedures for the separation, identification and estimation of thirteen nitre and nitres* compounds including six analogous pairs of sueh compounds • It Is Included as an appendix to this thesis* PART 32 - KXFEMMMTtt (A) Preparations: The following chemicals were commercially available from the Eastman Kodak Research Laboratory! p-*amiaophenol, p-chloroaniline, p-*aminobenzoie acid, p-nitrosodimethylanillne, nitre* benzene, p-ehloronitrobenzene, p~nitrobenzoic acid, p-phcnylazophenol, and p-diaethylaminoazobe.naene * p-Nitro toluene was obtained from the City

C hem ical Corporation of Hew Tork* p^itroaniline was obtained from the

Merck Company, and p-toluidine from the Elmar and Amend Chemical Company.

The parity of these compounds was checked by taking the melting points and comparing against the values given in the literature* Samples of the compounds were also chromatographed to determine whether any extraneous zones were formed due to impurities*

The following compounds were prepared by standard methods found in the literature or by variations of these methods: nitrosobenzene, p-chloronitroaoben zene, p-nitrosotoluene, 2-nitroresorcinol, p~nit.ro*- dime thylan illn e, p-choroaniline, azobenzene, azoxybenzene, p*phenylazo* toluene, p*phenylasobenzolc acid, p,p i-azoxyphenol, p,pl*asophenol, p-chloroazophenol, and p-chloroaniHne. In the following brief des** cription of the methods used, the melting points of the compounds agreed with the values found in the literature* "In the literature'* unless otherwise stated refers to the values found in Lange*s Handbook of

Chemistry, Sixth Edition, or the Dictionary of Organic Compounds, pub­ lished by the Oxford University Press*

Hitrosobenzene was prepared by the method of Bamberger (5) which involved the reduction of nitrobenzene to the hydroxylamine with ammonium chloride and zinc dust, followed by the oxidation of this compound to the aitroso compound with a cold dilute solution of potassium dichromate

43 44 and sulfuric acid* The nitroso compound precipitated* and was purified by steam distillation* It was found that the yield of the hydrexylamine could be increased and the reaction accelerated by allowing the tempera* tore to rise instead of maintaining it at 15-16° as called for by

Bamberger* 'Sis same method was used to prepare p-nitrosofcoluene and p-chloronitrosobensane from their corresponding nitro confounds. The yields obtained of these two compounds using this method were very small* An attempt to prepare them by the method of Alway (1) was unsuccessful* Steam distillation was used as the means of purification fo r these compounds also*

About 5 grams of 2 -aitro re so rc in o l was prepared by the n itra tio n , of resorcinol with n itric acid using the method of Kaufman and dePay (36)*

The orange red crystals were purified by recrystallization from dilute alcohol* and melted at 34°*

p-8itrodiaethylaniline was prepared by the nitration of dimethyl laniline hydrochloride with cold dilute nitric acid using the method described in Hoaben's* "Die Methoden Dear Organischen Chemie", Vol* 4* p* 189* The raw product was obtained with almost a quantitative yield and was purified by repeated recrystallizations from alcohol* It melted a t 163®.

p-Phenylazoben zoic acid was prepared by the method described In

Organic Synthesis* Vol. 25* p* 86* p-Aminobenzoic acid was dissolved in warm acetie acid and a hot* concentrated solution of the aitroso compound in acetic acid was added with shaking* The solution was allowed to cool s lo w ly and to stand overnight* The azo compound precipitated as orange red needles, which were purified by recrys taliization from alcohol* The uniting point agreed with the value given In the literature* 45 p-Phenylaaotoluene and p-ehloroaaobenzene w ere prepared using the flame method by treating nitroso benzene with p-toluidine, and p-chioro~ aniline, respectively*

Azobenzene was prepared by the method described by M ills (49) from nitrosobenssene and aniline* p-»Phenylhydroxylsaine was prepared by the reduction of nitrobenzene, with si m d u s t and ammonium chloride*

This compound was treated with nltrosobenzene in acetic acid to for® azoxybenzene* The crude aso and azoxybenssane were p u rifie d by repeated recryst& llizations from dilute alcohol, until their melting points a g re e d with the values given in the literature*

B* Chromatographic Characteristics* The adsorbents used in this w ork were Merck Reagent Grade S ilic ic Acid, Magnesium Oxide and Aluminum

O x id e, Johns--Manville Celite was used as a filte r aid* The solvents used w ere thiophene f r e e benzene (Merck Reagent Grade), acetone and purified petroleum ether (B*P* 65*67°) *

The adsorbents were standardized by the determination of the iTE° values, with respect to the®, of 0*6 cc portions of a 0*01 H solution of o-nitroaniline in benzene* See Table 17 A. This made possible the calculation o f the value for the compounds on any other adsorbent similarly standardized by the use of o-nitroaniline * The chromatographic characteristics of all the compounds were determined first on an adsorbent composed of three parts by weight of Silicic Acid to one part of Celite*

A three per cent solution of acetone in benzene was used as the developer*

In those cases where the adsorption was poor, or where two compounds had the same MR° value, the developer, adsorbent, or both were varied to improve the separation* Sufficient data were obtained to make it possible to devise ways to separate any two of the compounds used fro® each 46 other* The !,a« values and the conditions used in determining them are listed in Table IV, Each value given in this table is the average of that obtained from at least three runs* / The sensitivity, or the minimum concentration of a solution of the compound necessary to give a zone which could be detected, was determined for a representative group of these compounds, A standard solution of the compound in the proper solvent was diluted to a cancan** tration which would barely give a reliably discernible none when run on a column, using the same conditions of development as were used for the determination of the "R" value* Several of the compounds formed visible zones, while the positions of others had to be brought out through the use of streaking reagents* Some of the compounds reacted with more than one streaking reagent* In these cases, the sensitivity was determined using that reagent, which permitted the detection of the zone formed with the smallest concentration of the solution* The results of this work are given in Table VI* C* Spectrophotometric Curveas Standard solutions of known concentration of each of the compounds were made up in absolute ethyl aleehol* The solutes used for these solutions were purified carefully,

In most eases by re c iy s ta lliz a tlo n , u n til a product of optimum pu rity was obtained* The melting points were checked and samples were run on a chromatographic column to ascertain if impurities were present* The pure solutes were weighed on an analytical balance using calibrated weights* Using absolute ethyl alcohol as the solvent, 0*01 molar solu­ tions of the compounds were made up in 100 cc volumetries, in those cases in which the solubilities permitted* This gave weights of from 0*1 to 0*2 gr; ms of compound per 100 cc of solution, minimising losses due to weighing* 47

These standard solutions sere diluted to the proper concentra­ tions for giving satisfactory Beckman curves, using lacax retested pipets and Exax retested volumetric flasks* The smallest pipet used was 2 ml, and the smallest volumetric used ms 25 cc in order to keep errors of dilution at a minimum. The standard solutions, after dilution to the proper concentration, were run on the Beckman Model D* U* Ultra­ violet Spectrophotometer immediately after they were made up, in order to prevent any changes in the absorption which might occur on standing*

Absorption curves were obtained for the compounds in both the ultraviolet

(220 to 320 millimicrons) and the visible ranges of the spectrum* The concentration of the solutions were so adjusted that the absorption maxima would be obtained in the optical density region of 0*2 to 0*8. From the data obtained, a plot of wave length against molecular extinction co­ efficient ms made* The results obtained are tabulated in Table V and represented graphically in Figs. 9, 10, 11, 12, 13, 14 and 15*

D. Determination of the accuracy of the method in quantitative estimations. The procedure used In the determinations for this part was essentially the same as that described in detail in the attached appendix* The standard benzene solutions of the compounds made up for determining the "ft" values were used in this part of the work* A 3 cc aliquot of the solution, or a solution formed by the dilution of this solution, was put on a No* 2 column and developed, using the same condi­ tions as were used in the determination of the HRI* values. The column was extruded, and the tone containing the compound cut out* The zone was powdered, dried and eluted, and the eluent made up to volume. This solution was diluted, run on the Beckman, and the concentration 4$ calculated by comparison with the standard Beckman solutions.

From the data obtained by the above procedure, the percent recovery of each compound was determined* In Table VII are recorded the results obtained using benzene solutions of single compounds* The results obtained when using mixtures of equal amounts of solutions of sim ilar compounds are shown in Table VIII* TABLE IV

E VALUES OF SOME AMINO, NI TtOSO, NITRO AND RELATED COMPOUNDS

ADSORPTIVE ADSORBENT ADSORBENT ADSORBENT ADSORBENT 3 to 1 Silicic 3 to I Silicic Silicic Acid S ilic ic Acid - Celite Acid - Celite DEVELOPER Acid DEVELOPER DEVELOPER 3% Acetone DEVELOPER 3% Acetone Benzene 97% Benzene Benzene 97% Benzene p-aatinophenol .039 •02 p-ehloroaniline •507 • 151

p-aainoben*oic acid .075 .025 p-toluidine •390 .169

p-nit roaniline .395 .232

p-nitrediaethylaniline .185

2-nitroresoreinol • 642

p-nit robenzoi c acid .340 .02

nitrobenzene • 98 .733 p-nitrotoluene .678

p-chloror&t robenzene .681

nitrosobenzene .820

p-chloronitroso- •702 .970 benzene p-nitrosotoluene •681

p, p *—a zophenol .115 .00 p, p’-azcxyphenol .096

p-phenylazophenol .383 .205 p-nitrosodiiaethyl- .078 a n ilire p-chloroa zobenzene • 224 .156

p-ph enyla zot oluene .256 .145

49 TABLE IV (COKT33TOBD)

ADSORPTIVE ADSORBENT ABSORBENT ADSORBENT ABSORBENT 3 to 1 Silicic 3 to 1 Silicic Silicic Acid Silicic Acid - Celite Acid - Celite DEVELOPER Acid DEVELOPER DEVELOPER 3% Acetone DEVELOPER 3% Acetone - Benzene 97% Benzene Benzene 97% Benzene diaethylamino- *208 azobenzene p-phenylazo- .235 benzoic add

asobenzene *250

aaoxybenzene *156

USING MAGNESIUM OXIDE AS THE ADSORBENT AND 3% ACETONE - 97% BENZENE AS THE DEVELOPER

ADSORPTIVE «R!,

p-nitrosodimethylaniline *877

p-nitrodlmethylaniline *915

p,p1-azophenol .017

p,p* -azoxyphenol .011

2-nitroreeoreinol .0

p-nit roaniline .264

p-phenylazobenzoic acid *019

nitrobenzene .965

n it ros obenzene .897

50 USING ALUMINUM OXIDE AS THE ADSORBENT AND % ACETONE 9% BENZENE AS THE DEVELOPER

ADSORPTIVE p-nitrosodifflethylaniline .905 p-nitrodim ethylaniline *945 p-nitroaniline .556 p-phenylazophenol .437 p-aainobenzoic acid *166 p,pfazophenol *079 nitrobenzene 1*0

TABLE IV A

STANDARDIZATION OF ADSORBENTS USING O.OI U O-NITROANILINE

ADSORBENT DEVELOPER »R«

Silicic Acid Benzene .169

S ilic ic A cid - C elite Benzene *774

Silicic Add 3% Acetone *211 97% Benzene Magnesium Oxide 3% Acetone *659 97% Benzene

Aluminum Oxide Benzene *891

Note - The following streaking reagents were found to be useful in the detection of compounds which did not give visible zones •

Alkaline permanganate was fo r the amino compounds* A 1$ solution of resorcinol was used to detect nitrooo compounds* A hot solution of ammonium chloride and zinc duet in $0% alcohol gives a yellow color with n ltro compounds on the column*

51 TABLE V

Absorption Bata for the Compounds Studied in

Absolute Ethyl Alcohol

Wave Length Extinction Coefficient (millimicrons) (molar extin ctio n co efficien t X1(T^) I II III

310 3*95 7.54 315 4.36 7.90 320 4.87 3*52 Q.28 325 5.48 4.34 8.48 330 6.22 5*35 9.24 335 7.00 6.40 8.88 340 7.70 7.50 8.36 345 a. 38 8*40 7.93 350 8.80 9.35 355 9.10 10,00 360 9.20 10.10 365 9*10 9.95 370 8.60 9.40 375 7.80 8.65 380 7.00 7.4-0 385 6.02 390 4.94 4.65

(maxima are underlined) I p,pf-azoxyphenol IX p^-azophenol III p-phenylazobenzoic acid

52 Wave Length Extinction Coefficient (millimicrons) (molar extinction coefficienta 1Q~3)

IV V VI VII

225 .400 4. 6 B 4.17 4.59 230 .454 2.22 2.26 3.66 235 .560 2.26 1.86 4.41 240 .712 2.92 2.27 5.61 245 •880 3.78 2.99 7.05 250 1.050 5.23 4.05 8.49 255 1.170 6.82 5.36 9.63 260 1.190 8*46 6.84 10.05 265 i . i i o 9.62 8.06 9.90 270 .930 10.03 8.90 9.00 275 .730 10.00 9.12 7.65 280 .552 9.40 8 W 6.09 285 .410 7.95 8.00 5.01 290 .306 6.32 6.82 4.02 295 .228 4.79 5.52 3.15 300 .160 3.27 4.10 2.76

IV nitrobenzene V p-chloronitrobenzan© VI nitrotoluene VII p-nitrobenzoic acid

53 Wave Length Extinction Coefficient (Millimicrons) (molecular extinction coefficient X10“3)

VIII IX X XI 220 5*72 6.08 225 6*66 MS 7.78 230 6 0 6 6.58 g.23 235 2.86 7 J 3 240 Of 94 1.06 6.60 245 5.52 250 1.00 6.03 255 1.60 6,57 260 1.84 1.68 2.40 6.78 265 2.88 2.61 3.75 270 4f32 4 .1 2 5.00 6.30 275 6.08 5.80 6.42 280 7.70 7.44 7.05 285 9*22 9.12 7.20 290 9.72 9.35 S .® 295 9^00 9.05 5.75 300 8.96 9.58 5.40 305 5.20 310 5.02 315 4.50 320 4*00 325 3.05

(Maxima are underlined) VIII p-chloronltros©benzene II p~rdtros©toluene X nitros©benzene XI. azoxybenzen©

54 'teve Length Extinction Coefficient (millimicrons) (molecular extinction coefficient)

XII XIII XIV XV

220 4.88 4.55 3.06 5.68 225 6*62 6.35 4.07 4.74 230 3,50 7.50 6,10 2.90 235 ?.15 8.75 8.46 1.34 2X0 7.70 7.50 10.60 .96 245 5.15 6*40 1.32 250 2.30 3.90 9.43 2.18 255 1.48 1.94 6.50 3.26 260 0,77 .89 3.23 4.76 265 0,48 .59 6.36 270 0,53 .69 .60 8.04 275 0.78 .97 9.34 230 1,02 1.30 10.18 235 1.57 1.61 10.74 290 2.05 1«76 10.76 295 2.47 TT©4 o6.od 300 2.70 1.33 8.56 305 2,6 2 .94 6.26 310 2.22 .59 3.70 315 1.67

XII p-aminophenol XIII p-toluidine -IV p-chloroanillne XV p-aminobenzoic acid

55 Wave le n g th Extinction Coefficient (millimicrons) (molecular extinction coefficient X10~3)

m x r a XVIII XIX XX

220 8.24 4.68 4.84 7.50 225 10,55 5.08 6,72 7.00 a ,00 230 12.00 5*12 7.08 8.00 0.64 235 11.0$ 4.46 7.32 8.30 9.06 240 7.83 4.2 2 o79o 1*55 245 6.00 7^80 250 5.60 6.78 255 6.02 5.02 260 8.52 6.18 265 9.42 17?o 270 10.32 5.10 275 10. Vt 280 9.60 285 0.42 290 8.22 295 11.22 300 13.25 305 15.45 310 17.35 315 18.80 320 20.22 325 22.30 330 19.75 335 19*05 340 16.65

(Maxima are underlinedj XVI p-chloroazobenzene XVII p-nitroanilina XVIII p-nitros odimethylaniline XIX azobenzene XX p-phenylazopheno!

56 ?®Y® length Extinction Coefficient v

XXI XXII XXXII XXIV

310 16.00 315 13.40 320 19.30 325 5.00 20.40 330 3.58 5.66 B 3 335 4.96 6.36 13.40 340 5.60 7.18 16*40 345 7.05 7.90 14.40 350 8*64 8.86 355 10,40 9.70 360 12.30 30.30 365 14.15 10,90 370 10,00 15.95 11.24 375 11.95 17.42 380 14.00 18.88 11.20 385 15.70 19.25 10*90 390 17.41 19.35 10.24 395 19.28 I 7 T30 400 20.60 I 6.65 405 21.05 410 21.15 415 20.79 420 19.65 425 18.65 430 16.30 435 15.30

(Maxima are underlined) 1X1 p-dimethylaainoasaobenzene Aiil p-nitrodlmethylaniline 1XEII 2 -n itrareao rcin o l 4a IV p-pfaenylazotoluen©

57 TABLE VI

SEESITIVITY OP METHOD FOE DKTKRMITOG THE ZONES

p-aainophanol — ----- * — ------0.0002 M p-nltroaniHn* ------0.00005 If p-a»inefe«n*©ic------0.0002 H p-nitrosod±aethylaniliEie ------— 0.00001 M p-nitrosotoluene ------0.00004 M nitros obensene - - - — ------_ ------0.00004 M

2-nitror«sorcinol ----- « ------0*0005 M p-nitrodieethylimlllne - 0.00004 M nitrobenzen* ------— — ------0.0004 M asobensene ------» — - — 0.00002 M j>-djj»thylajainoazobenzene 0.00005 M p-phenyl&eophenol 0.00004 M

58 TA BU V I I

QUANTITATIVE RECOVERY BY MEANS OF THE CHROMATOGRAPHIC AND SPECTROFHOTOaBTRIC METHOD

CONCENTRATION AVERAGE CALCULATION COMPOUND or BENZENE SOLUTION % RECOVERY BY METHOD p-Ritro*odijaethylanilin« 0*01 M w% p-idtrod±ii»thyl*nillne 0*01 M 9956 p~dlB8tbjrlaminoasobdn2dn« 0.005 M 98* nltrosobense&e 0.01 M 97% nitrobenzene 0.01 M 96% p-p1-**©ph*nol 0.004 M 98* p-phenylaiophaaol 0.004 M 99* p-phenylazoben*oic acid, 0.004 M 97* p-nitroaniline 0.004 M 98*

59 TABLE V III

ANALYSIS OF SOME MIXTURES OF THE COMPOUNDS STUDIED IN THIS WORK

CONCENTRATION % RECOVERY BY METHOD MIXTURE IN SOLUTION * COMPOSITION BASED ON COMPOSITION

X* p-nitroeodimethylaniline 0.005 « 50% 48.5* and p-nitrodimethyl&nillne 0.005 M 50% 49.5*

2. p-toluidine 0.0033 M 33* 32* p-nitrosotoluene 0.0033 * 3% 32.5* and p-nitrotoiklene 0.0033 H 33% 31.5* 3« p-an&nobenaoic acid 0.005 M 80% 79.5* and p-nitrobenzoic acid 0.00125 U 20% 18* 4. Pjp'-azophenol 0.005 U 50% 49* and p^p’-asoxyphenol 0.005 u 50% 50*

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> u> \ o ' N 3S \ r\ v *0 \ CO C* PART I I - DISCUSSION OF RESULTS

The first phase of this work was devoted to the preparation of the compounds which were need in th is study. Since these preparations in­ volved the use of standard methods found in the literature, or variations of these methods, very little attention has been given to the description d e ta ils . The methods used and any remarks which seemed p ertin en t were discussed in "A" of the previous section entitled BFart II - experimental”.

Adsorption varies with the nature of the adsorbate (or compound adsorbed) and the conditions of Its development on a column* Among those factors which affect the adsorptivlty of a compound are the electro­ negativity of the substituent groups, hydrogen bonding, steric hindrance and the geometrical arrangement of substituent groups about the benzene rin g .

Adsorbents vary widely in their strength and capacity to perform separations. Solvents vary also in their ability to develop or move the semes down a particular column of adsorbent. A Variation in conditions

(adsorbent and solvent) will not only cause a variation in the rate of movement of a sons for a particular compound but will generally cause a different change in the rates of movement of the sones for different compounds. Seeping the above facts in mind, the chromatographic character­ istics of the compounds studied were determined under varying conditions.

The data obtained are tabulated in Table IV; the nR” values listed are the average of at least three determinations. The concentrations of the solutions used were 0.01 molar or less with respect to the solute.

Prom a consideration of this data, it should be possible to select those conditions of development necessary to obtain the separation of any two

67 68 of the compounds studied*

From the results obtained, the following generalisations can be made* The substitution of certain groups into th e benzene ring cause an increase in the adsorptivity of the compound* Using silicic acid as the adsorbent, and benzene as the developer; the effect of the functional groups on adsorption in the order of decreasing adsorptivity appears to be - OH y - COOH^- ^ 2^ *** K These groups are strongly adsorbed and are referred to as principal groups whereas the less strongly ad­ sorbed groups are referred to aa secondary or modifying groups. These groups in many cases alter the activity of the principally adsorbed group.

When two strongly adsorbed groups are present in the molecule the effect on adsorption Is additive and the *H“ value is decreased* The substitution of a strong electronegative group in the para position to a principal group weakens the hydrogen bonds at the other end of the molecule and thus increases the adsorptivity* .However, when a highly electronegative group, such as the nitro group is substituted in the ortho position to a principal group, the flRw value is Increased, probably through the fomation of "internal” hydrogen bonds*

The effect of the solvent and developer varies with the polarity ©f the adsorptive and the solvent. When separating two compounds on an adsorbent from bensene, the more polar of the two would be the most strongly adsorbed* The adsorbents used were standardised with a 0*01 M solution of o-nitroanilin® • This compound is widely used for this purpose by workers in the field, and makes possible the calculation of the "R” values for the compounds on any other adsorbent slm illarly standardized by the use of th is compound. 69

The sensitivity of the detection of the zones was not determined

for all of the compounds studied, but was investigated for at least one

of each of the types of compounds used* In the case of some of the

compounds in which streaking reagents were used (p a rtic u la rly the u ltra

compound®), the sensitivity varied with the manner in which the streaking

reagent was made up. The sensitivity was also found to vary somewhat

with the combination of adsorbent and developer used in the determination of this quantity.

The Beckman results are tabulated in Table V and are represented

graphically in Figs. 9-15. The absorption of all of the compounds used was investigated in both the ultra-violet and the visible regions of the

spectra. However, only those portions of the results are presented here which would be of use in the id e n tific a tio n of the compounds;

Solutions of all the compounds in absolute ethyl alcohol were found

to obey Beer#s Law very closely in the optical density rang© from 0*2 to

0.8} therefore the equation of this law could b© used in th© quantitative

estimation of solutions of unknown concentration*

At the beginning of the study described in Part III erratic results

mire obtained in the quantitative determination of the amount of p-nitroso-

phenol in the solutions. On further investigation it was found that the

absorption maxima for solutions of nitrosophenol in alcohol vary with the

amounts of water In the alcohol. Thus on using absolute alcohol as the

eluting agent discrepancies were obtained in the results, in all proba­

bility due to the relatively rapid absorption of atmospheric moisture by

the alcohol. It was found that on using 95% alcohol for the Standard

Beckman Curve, th© maxima came at the same wavelength but was g reater than when absolute alcohol was used. This would indicate a solvent effect on

the p-nitrosophenol - quinone monoxim© equilibria. part xx * sm m i

The chromatographic characteristics of some amino, nitroso, nitro, wo* and azoxy compounds, (twenty-four in number) have been determined*

The behavior of these materials on a chromatographic column has been studied and sufficient data obtained to permit the separation of a m ixture of any two of these compounds*

Standard spectrophotometric absorption curves have been constructed for these compounds* A method has been developed for their further identification, and their approximate estimation, following their chromatographic separation and purification*

The efficiency of the combined chromatographic and spectrophoto­ metric procedure, as a means of analysing mixtures of these compounds was studied* The results obtained suggest the general efficiency of this procedure as a means of analyzing m ixtures of these compounds, p a rti­ cularly adaptable to small quantities*

70 pai $ h i - otixsucxion

During some of th© work described in Parts I and I I of this thesis, it was observed that a variety of changes took place in solutions of scoe n itro and nitro so compounds, p a rtic u la rly th e l a t t e r , and p a rticu la r­ ly'when such solutions were exposed to light and to high temperature.

This in itself was not surprising, but it was further observed that in

SD99 instances, the changes which took place when both types of compounds were present differed significantly from those occurring when th© solution contained only one. Such observations suggested th© desirability of examining th© behavior of systems containing a nitro compound and a n itro so compound, to ascertain a s fa r as possible the existence, extent and nature of the interactions between them, if any, and of any indirect influences either might exert upon the decomposition c£ the other. Part

III of this thesis describes initial steps In such a study*

The various compounds which stand at intervals along the oxidation* reduction path between the nitro compounds at one extremity and the amines at the other include sons types which possess great commercial value, and others which, lacking in practical significance, still are of much theoretical interest# Most of the standard procedures used in progress­ ing fro® one point to another along this path were developed at early dates and are generally familiar. In th© practice of some of these processes, hot/ever, one may observe considerable evidence of a complexity of action which is not suggested by the equations conventionally employed to represent them* In addition to th© action of the selected oxidizing or reducing agent, there exists an undercurrent of more limited oxidations, reductions, condensations, and other changes, exerted upon each other by the initial and final organic materials and by such Intermediate products

7X 7 2 as may be formed, by the way# Sometimes these interactions attain very m aterial proportions^ and introduce a surprisingly large number of new molecular species into the originally simple reacting system,* They may exert major influences upon the identities* the relative quantities* and t h e degrees of purity of the actual final products* Studies of these in-* teractions* comprising as they do the ebb and flow of an intricate net** work of equilibria* tend to yield data which are too elaborate fo r re a d y interprets! ion*

In order to reduce th e complexity of the system and possibly gain sons insight into the nature of some of these interactions* it should prove profitable to investigate systems which contain only a small part of the field* I t was thought that a system which contains a nitro and a n itro so compound might lend itself particularly w ell to an investigation of t h i s sort. Since t h e n itro compound represents the state of maximum oxidation in the reaction s e r ie s * i t should react only in such a way a s to give a reduced compound. Nitroso compounds on the other hand a re known to re a c t i n other ways, in addition to their expected oxidation*

These compounds stand adjacent to each other in the oxidation-reduction se rie s ; and this fact* coupled with the fact that one of them is limited i n i t s direction of reaction* should simplify any primary and secondary reactions between them to an extent which w ill make it possible to fo llo w their course w ith more certainty than if both compounds were more re­ active or more widely separated in the oxidation-reduotion scries*

K ltro compounds have been used in some instances as oxidising agents* and are of particular value in some specific processes which require mild oxidants# It might be possible therefor© by the proper choice of nitroso and nitro compounds and under certain conditions to V cause the following reaction to take place:

&4*0 2 / X-HQ — X-HQ / T-NG2 As pointed out in the introduction to Part I, methods of nitrosation end the special orienting influences of the nitroso group make it possible to obtain certain nitroso compounds in good yield and free from isomers, where this could not be done directly for the analogous nitro compounds*

The possibility of using appropriate nitro compounds for subsequent oxi­ dation of such nitroso compounds appeared to deserve exploration*

There are almost innumerable publications which deal with reacting systems in which nitro confounds are reduced, nitroso compounds are oxidised, nitro compounds act as oxidants, or in some manner nitro and nitroso compounds are present at the same time in the same system; but no article was found in the literature specifically describing the inter­ action of nitro and nitroso compounds. However, in view of the use of ultra-violet light in seme of the present work, the following references are pertinent:

Bamberger (6 ) noted that nitrosobenzene in solution, when exposed to light, decomposed to give tarry residues. He was able to isolate and identify asoxybensene, nitrobenzene, aniline and o-hydroxyazohenzene from this residue* Other products appear to have been formed which he was not able to separate and identify* Yechiotti and co-workers (62) published three articles which des­ cribed the effects of ultra-violet light upon systems containing nitro compounds, and in some instances their reduction products* They also described the oxidation of aniline with nitrobenzene in the presence of sunlight; this reaction did not proceed at all in its absence. A large variety of products were isolated from the reaction mixture; the Initial reaction, however, was thought to be 7k

d > *02 / 0 * « 2 * _____> =0 / <3 HHOH followed by numerous successive tactions, and possibly accompanied by side reactions.

The objects of the study of which th© present work may be consider­ ed the beginning were ( 1) to investigate the interaction of nitroso and nitro compounds, when both are present in the same solution* ( 2) to study the effect of varying the conditions of the reaction on these inter­ actions, if any were found to exist; ( 3) to isolate and identify th© re­ action products, if any ire formed 5 and ( 4 ) to study th© indirect influences, if any, which each exerts upon the thermal and photochemical decomposition of the other*

For the Initial work, solutions of a known concentration of a nitro and a nitroso compound were made up and allowed to stand under the selected conditions for specified lengths of time* The nitro compound in each instance was nitrobenzene, p-chloronitrobenaene, nitrotoluene, or p-nitrobenzoic acid (in the majority of cases the first-named); the nitroso compound was p-nitrosophenol, or p-nltrosodimethylanHine* At the end of specified time intervals, aliquots of the reaction mixture were with­ drawn and analyzed by chromatography and spectrophotometry. The amount of the original nitroso compound which had undergone decomposition or reacted was determined, and in some instances the chromatographic and speetrophotomstric characteristics of the by-products of th© reaction, If any, were investigated. The solutions in some experiment® war© allowed to stand at room temperature, with no intentionally-introduced accelerat­ ing influences. Others wore subjected to elevated temperatures, ultra­ violet light, excess nitro compound, potential catalysts, or a combination of some or all of these factors. In ©very case, a solution containing 75 th® nitroso compound alone, was subjected to exactly the same conditions at the same tine, and analysed in th© same manner as the solution con­ taining the nitro compound; this solution serving as a blank for comparison purposes* PART I I I * RXPERIMKHTAL

(A) P reparations: Th© p-nitroeophenol used in th is work was pre­ pared by acidifying a solution of tho sodium salt of p-nitrosophenol obtained from Kastman Kodak Research Laboratories with dilute sulphuric sold in an ice bath* Th© crude product was filtered, washed with cold water and taken up in ether* After decolorizing the ethereal solution and filtering, the ether was distilled off and the nitroso compound purified by recrystallization from ether and petroleum ether* The p-nitrosophenol obtained in this manner consisted of light-yellow crystals which turned dark at 126-128° and decomposed at 142-144°. This agrees with the description of the compound given in the literature.

The p-nitrosodiiaethylaniline was obtained from Kastman Kodak. On chromatographing a sample of th is compound, two zones were obtained in addition to the zone given by the nitroso compound, indicating that impurities wore present* On recrystallization from benzene and petroleum ether, the melting point was 85-86°, which was in agreement with that given in the literature* The preparation of p-nitrodimethylaniline is described on page 44, In Part II of this work* The p-nitrobenzoic acid, a* p. 240° l p-chloronitrobenzene, m.p. 83°) and nitrobenzene, b*p« 210° were obtained from the Kastman Kodak Research Laboratory* The p-nitro- toluene, sup. 53° was obtained from the City Chemical Company* Since the melting points of these compounds agreed with the values given in the literature, and since no extraneous zones were obtained on chromato­ graphing samples of them, they were used without further purification*

The chromatographic characteristics and the spectrophotometric data for the compounds used in this work were obtained, .and are

76 77 tabulated either in Part II or in the attached appendix,

(g) Procedures Solutions were made up containing known concentra­ tions of one nitro and one nitroso compound in a suitable solvent and exposed to varying conditions of temperature, time of contact, ordinary or ultra-violet light, and catalysts. As quickly as possible after the specified time intervals, samples of these solutions were chromatographed, and quantitative estimates made apectrophotometrically of the original nitroso compound which remained, together with (in some instances) other components of the final mixture* The accuracy of this method of quantita­ tive analysis with respect to the components of these systems was cal­ culated to be on the order of £ 2 % of the actual amounts present in the solutions, varying a little with their identities* In all cases, a solution containing the same concentration of the nitroso compound, but no n itro compound, was exposed, sim ultaneously, to th e same conditions as the reaction solution and analysed in the same maimer, thus serving as a blank for comparison* The results of these runs are tabulated in

Tables IX, X, XI and XII* (C) Reactions of p-nitrosodim sthylanillne w ith n itro compounds*

The results of most of these runs are tabulated in Tables IX and

X* In runs 2 through 6, Table IX, three visible sones were obtained*

They were, from the top of the columns {X) a brownish-green sons identified as unreacted p-nitrosodimethylanilinc; (2) an unidentified orange zone and (3> a zone Identified as p-nitrodlmethylanlline. The reaction solutions of these runs changed slightly in color during the reaction periods, from green to a yellow-green* On standing for several days after the reactions were run, a gradual change in color to a brownish green was noted* There was very little change in the appearance of the solutions noted in runs 7 through 14 other than a slight darkening 7 a In run #14, which contained p-nitrophenol.

In run #15, p-nitrosodimethylaniline was heated to a high tempera­ ture with nitrobenzene. The color of the solution changed from green to a dark brown, and it appeared to contain a suspension of dark particles.

On chromatographing an aliquot of the reaction mixture in benzene, five tones were obtained. From the top of the column they were as follows:

(l) a tarry material which did not penetrate the column appreciably, and contained an alcohol-soluble component} (2) p-nltrosodiinsthylaniline;

(3) a pale yellow zone containing an unidentified material} (4) an orange yellow zone containing an unidentified material; and (5) p-nltrodimethyl- aniline. No satisfactory blank could be devised for comparison with this run. Attempts to replace the nitrobenzene with inert materials (diphenyl, for example) led to highly erratic results which could not be duplicated.

In the dye industry, ferrous salts have sometimes proved effective as catalysts for high-temperature oxidations with nitrobenzene. This fact suggested the following experiments

A 0.04M solution of the nitroso compound in nitrobenzene was made up. Ten mg. of ferrous su lfa te was added to a 75 co. portion of th is so lu tio n which was then heated to 200° fo r 6 hours* The solution became dark brown, with some solid matter appearing. The loss of nitroso compound was 47$. The reaction products appeared to be so diverse, and the analyti­ cal procedure of such doubtful reliability in these circumstances that this run has not been entered in the tables, and no other runs were made under similar circumstances. In Table X are listed the conditions and results of reactions in which p-nitrosodimethylaniline solutions containing in some instances a nitro compound were exposed to ultra-violet light. Th© ultra-violet light 79 sources used were UA 2 and H 2 mercury vapor lamps* The H 2 latqp used fo r runs 16-19 did not radiate ultra-violet light of as great intensity as th e UA 2 lamp used f o r the r e s t of those in which such lig h t was employed*

th e physical appearance of the solutions In runs 16-19 did not change appreciably on exposure to ultra-violet, except for a alight fading of the color* the same was true of runs 20-23* Small amounts of flocculent precipitate were noted in some of these reaction mixtures at the end of the reaction, and on standing several days after the reaction had been completed small amounts of tarry materials settled out on the sides of the reaction flask* The solution of run 25 containing p-nitrophenol had darken­ ed visibly at the end of 1 hour, and was opaque by the end of 3 hours* A email amount of a dark tarry material precipitated*

(D) The reaction of p-nitrosophenol with nitro compounds*

The results of those runs in which p-nitrosophenol and a nitro com­ pound were heated together under ordinary conditions of light are tabulated in Table XI, and those in which mixtures of p-nitrosophenol and a nitro compound were exposed to ultra-violet light are given in

Table XII* h Q*0i*M solution of p-nitrosophenol in acetone was made up and used in runs 26, 29, 32 and 33* A saturated solution of p-nitrosophenol

(approximately Q.005M) was made up in benaene for use in the rest of the runs* With the latter, samples of known volume of the nitroso solution were chrcsiatographed and run on the Beckman before exposing the solutions to the conditions of the reaction* Then by going through the same pro­ cedure after completion of the reaction, the loss in p-nitrosophenol could be measured* There was very little change in the physical appearance of the solu tion s at the completion of rune 28 and 29, except for a slight fading 80 of th© green color t© yellowish-green. However, on standing for several days, these solutions slowly became brownish-green.

Ho detectable change took place in the physical appearance of the solutions during runs 30 and 31, or after standing for several days.

These two solutions were allowed to stand in the dark, at room temperature, for a week after completion of the runs, with samples withdrawn for an aly sis a t in te rv a ls . Fig. 16 shows the small change on standing, following the greater change during the period of heating. Using acetone as a solvent (Runs 32 and 33) and exposing the solutions to ultra-violet radiation, there was observed a pronounced color change, from dark green to brown; the solution containing the nitrobenzene becoming a paler brown

(changing less) than the solution which served as a blank. These solutions became increasingly darker upon standing for several days after the runs had been completed.

As in runs #30 and #31, the solutions of runs #36 and #37 were allowed to stand in the dark at room temperature for an additional eight days, with samples withdrawn for analysis at intervals. These results also are represented graphically in Fig. 16, which gives a plot ©f the decrease in p-nitrosophenol with ties. This particular pair of runs was repeated twice more under the same conditions. The results of the three sets of runs agreed qualitatively, and were in approximate though not precise quantitative accord. In run §Uk (not tabulated) a solution of p-nitrosophenol in benzene was exposed to ultra-violet for 8 hours as in runs #34-#37. At various time intervals during the reaction aliquots were withdrawn and analysed for p-nitrosophenol content. Fig. 17 shows the variation in the rate of photochemical decomposition with time of exposure to ultra-violet light. a i Two similar runs gave approximate checks of #44.

A series of runs (mot tabulated) was made which involved acqueoua solutions of the sodium salts of p-nitrosophenol and p-nitrobenzoio acid.

Two acqueoua solutions containing 1.2? gm of the sodium salt of p-nitroao- phenol each in 93 <*c. of slightly alkaline solution were made up, one containing 10 gm. of p-nitrobensoic acid, the other containing 1.46 g.

An appropriate blank was also made up. These solutions were allowed to atand in stoppered flasks, in th© dark, for ten weeks at room temperature.

On analysis at the end of this time, it was found that the rdtroaophenol contents of these runs were identical (within the limits of experimental error). The solutions were then refluxed for 6 hours, and re-analysed.

No appreciable change in the nitrosophenol content of the solutions could be detected.

Equiaolar quantities of dry p-nitrosophenol and ra-nitrobenxoic acid were mixed in a closed test tube and immersed in a heating bath. At 120°, the mixture melted rap id ly , with bumping which suggested a sudden reaction.

The molten material was held at 120*122° for fifteen minutes and then allowed to cool. The residue was extracted repeatedly with acetone, in which it formed a red solution (in contrast to the yellow-green color, characteristic of p-nitroeophenol) • The loss in p-nitrosophenol was 75$*

Soma p-nitrosophenol alone was treated in th© same manner as the above.

It darkened but did not melt. The loss of p-nitrosophenol was 7%.

It was noted that on chromatographing some of the benzene solutions of p-nitrosophenol which had been exposed to ultra-violet light, additional zones were obtained. In order to identify additional products of this or similar reactions, chromatographic and spectrophotometric characteristics of a number of compounds potentially capable of appearing among them were determined, the data on these compounds Is tabulated in Part II. One of the zones obtained ms identified as p,pf~a zoxyphenol by comparing its chromatographic and spectrophotometric characteristics vdth those

©f a known sample of the same material* BEHAVIOR OF MimOSOTEJETHILABILINE WOT HIIEQ CCMPOM5BS UJ ORD3UARI LIGHT

Cone* of Identity and Loss o f Formation N ltrese Gene* o f N itroso o f N itre Baa # Solvent Teiap* finas Compound N itro Compound Compound Compound

l(BXank) Acetone 24* 4 weeks 0*05 M* None Zero Zero ft/O a Acetone 4 weeks 0.05 M. 0.05 M. 0.2g nitrobenzene

3 Acetone 4 weeks 0. 05 H* 0.5 iU 0.9* nitrobenzene

4 Acetone &° 4 weeks 0,05 M. 0.05 M. 0.2* p-nltrobenzoic acid

5 Acetone 26° 4 weeks 0.05 M, 0.05 M. % 0.2$ p-nitrotoluene

4 Acetone 26» 4 weeks 0.05 M* 0.05 M. % 0.2$ p-c hloroni trobenzene

7(Blaak) Benzene ao® 18 h rs . 0.05 M. None 2jC Zero

8 Benzene 80° 18 h rs. 0.05 M. 0.05 M. nitrobenzene 0.4)1

9 (Blank) Benzene 80° 18 h rs. 0.05 M, None % 0.1* TABX3 IX GOHTBHIEB

Cone, of Identity and loss of Formation N itroso Cone, of Nitroso of Nitro Run # Solvent T i m Gestpeuad N itro Compound Compound Compound 10 Benzene 80° 18 h rs. 0.05 M. 0.1 5% oM p-nitro toluene

18 h rs, 0.05 M. 2er©

12 18 hrs* 0.05 M. 0.1 M. 0.2$ nitrobenzene

13(Blank) Benzene 12 hrs* 0.D1 M. None 3$ 0,25$

14 Benzene 30» 12 hrs. 0.01 M. 0.1 M* 5$ 0.3$

15 Nitrobenzene 205-210 3 hrs. 0.1 H* concentrated 24$ 4.6$ nitrobenzene BEHAVIOR OF P-SraoSOBIMSTHYLANItlHS WITH \ NITRO GOHPOiJNDS UHBSH TIE 3HFIDEHCE OF I'MBA-VIOLST LIGHT

Gone, o f Id e n tity and Loss of Formation N itroso Gens, of N itroso o f N itro Em # Solvent Temp* Tim Compound N itro Coropound Compound Compound

16 (Blank) Benzene 26° 1 h r. 0.05 M. None 2$ Zero

1? Benzene 2&° 1 h r. 0.05 a. 0 .2 H. 1$ 6.2? nitrobenzene

18(Blank) Benzene 70° 8 h rs . 0.05 M. Bone 5$ 0.2? 19 Benzene 70° 8 h rs. 0.05 M. 0.2 M. 1% l . l g nitrobenzene

20(Blank) Benzene 80° 8 h r s . 0.025 M. Hone n.5% not determined

21 Benzene 80° 8 h rs. 0.025 M. 0.05 M. 10.5? not nitrobenzene determined

22( Blank) Benzene 80° S h rs. 0.025 M. Hone X3.55C not determined

23 Benzene 80® B h rs. 0.025 M. 0.05 M. 13.5? not nitrobenzene determined a. w

86 ©uozooqo^ju $€ *H 2*0 500* 0 *«•*? 0 ©08 ©U©fc89g t€

« r 880$ 500*0 *SJ^ $ ©08 8U8Z8©g

©oozuoqax^jo 3W 2*0 90*0 *SJT| 4f oQ9 &U0^90Y 62

$9 880M 90*0 •saq ^ ©09 sooqeoy pynocfeioo punocJgjOQ osoa^JK ptfnoduroo •c%oX ^U©AXOg # gso ^ tm JO *0800 OSOJ^T$ jo seoi poo JO *0800

iHOii iim ano ml SCMOdJtOO OmiH H£Ii* lOKSHdosomtfMi.o mumm n mass, t mrn m BEHAVIOR OF P-HXTSOSGPHBH0L ITH mmo compounds under m z btfiumce of ultra-violet m m

Difference Dae Cone* o f Id e n tity and lo ss of to Inhibiting Nitres© Cone, of N itroso Action of Etta # Solvent Tes$>* Time Compound H itro Compound nitrobenzene

32(Blank) Acetone 60° 4 h r3 . 0*04 H. Hons 12% 6% n Acetone 60® 4 h rs. 0*04 M* 0.2 M* (>% nitrobenzene

34(Blank) Benzene 80° 8 h r s . 0.005 M. Hone 2 7% 17% 35 Benzene 80° 8 hrs* 0*005 M* 0*02 M. loss nitrobenzene

36(Blank) Benzene 80® 8 hrs* 0*005 M. Hone 27% 13SS 37 Benzene 80® 8 hrs* 0*005 M. 0*02 M. 14SS nitrobenzene

38(Blank) Benzene 80® 8 h rs . 0.005 M. None 26.5 7% 39 Benzene 80° 8 h rs. 0.005 M. 0*001 M. 19.5 nitrobenzene TABLE XII GGBTBRJSB

Difference Due Gone# of Identity and Loss of to Inhibiting Hifcroso Gone, of Mtros© A ctio n o f Run # S o lv e n t Temp# Time Compound N itro Compound nitrobenzene

4G( blank) Benzene 84° 8 hrs* 0.005 M. Sone 36.5 9*551 4 1 Benzene 84° 8 hrs* 0*005 M. 0*001 M* 27% nitrobenzene

42{Blank) Benzene 80° 8 h rs. 0*005 M. None 32% 20 $ 43 Benzene 80° 8 h rs. 0*005 M* *00001 M* 32% nitrobenzene i £ oss £ o-/7//rosophsno/ p f % %

T/m

M actloaf of P-nitrosodime thylaniline with nitro compounds»

With reference to the results of Runs 1-6, it may be observed

that the araail changes in the loss of p-xiitrosodimethylaniline and the

formation of p-nitro dime thy laniline are so close to the limits of possible experimental error that any one euofa run should not be regarded

as significant* From the results of these runs, it may be concluded

that a t room temperature, and in ordinary light there w&a very little

interaction between the nitroso and nitro compounds. What reaction there was, appeared to be principally a spontaneous decomposition of the n itro so compound; the participation of the nitro compound, appeared to be

relatively small*

However, participation of the nitre compound did not appear to be

altogether negligible; there was a little more decomposition of the

n itro so compound when a n itro compound was present than there was In i t s

absence*

Oxidation of the nitroso compound to the analogous nitro confound was usually one o f the reactions which took place, but it was usually m ail compared to other reactions* The possibility of synthesising nitro

compounds in useful q u a n titie s by th is method seems remote* Hun #7 indicated some thermal decomposition of p-nltrosodimethyl-

aniline at 80°, but no auto-oxidation to the corresponding nitro compound.

Run #8 showed a slightly increased loss of p-nitrosodimethylaniline, with formation of a trace of p-nitrodime thy laniline when a nitro compound was

present* The results of runs 7-12 did not differ greatly from those of

92 93 runs 1-4* The increase in temperature from 26° to 60° appeared to accelerate the same reactions to a rather small extent* Ho substantial difference In the speed or nature of the reactions appeared to be produced by varying the id e n tity of the n itro compound employed*

At higher tea^eratures, thermal decomposition became relatively rapid; but again, any p a rtic ip a tio n o f the n itro compound, or any influence exerted by it, appeared to be small compared to the spontaneous thermal decomposition of the nitroso compound itself*

Irra d ia tio n by u ltra -v io le t lig h t produced a marked acceleration in the rate of decomposition of the nitroso compound (Runs 16*19) but here again, photochemical decomposition appeared to be materially greater than apy actio n o r influence of the n itro compound, though the l a tte r ! usually increased the amount of such decomposition to a limited extent*

Contemplation of Runs 1-27 led to the conclusion that interactions of n itro compounds w ith p-nitroaodim ethylaniline were quite sm all in proportion to thermal and photochemical decompositions of this particular nitroso compound* Little difference could be observed in the actions or influences of nitrobenzene, p-chloronitrobenzene, and nitro toluene*

However, when the nitro compound was p-nitrophenol (Run #25) and the reaction mixture was irradiated with ultra-violet light, the decomposition of the p~nl tro so dimethyl aniline was accelerated sharply*

When nitrobenzene was used instead of p-nitrophenol, under other­ wise id e n tic a l conditions (Runs 21 & 23), no sig n ifican t difference could be observed between runs made with the nitro compound, and runs made without it* Ibis suggests that the marked effect of p-nitrophenol was due to the fact that the latter was a phenol, rather than to the fact th a t i t was a n itro compound. This appears to deserve fu rth er study. %

In view of the fact (discussed la the paragraphs immediately following) that p-nitrosonhenol responded in an entirely different manner to the presence of nitrobenzene, it seems apparent that the Identity of the nitroso compound involved is a major factor in determining the inter* action o r influence* i f any* of n itro compounds on n itro so compounds.

The marked difference in the influences exerted by nitrobenzene and nitrophenoi, respectively, on p-nifcrosodimethylaniline, makes it equally apparent that the identity of the nitro compound may* similiarly be a major factor* This reaction should be more thoroughly investigated, how- over, before arriving at any definite conclusions.

The reactions run in nitrobenzene at high temperatures indicate that a great deal of thermal decomposition takes place under these condi­ tions* with very little interaction. The effect of ferrous sulfate was not studied sufficiently for comment at this time*

(B) Reactions of p-nitrosophenol with nitro compounds*

When p-aitrosophenol was used as the nitroso compound, and was treated with nitrobenzene, either at elevated temperatures* or in ultra­ violet light (or both), the results were drastically different* The same acetone solution of p-nitrosophenol was used for runs

28* 29 and 32, 33. The continued deepening of the brown color upon standing for several days after the runs had been completed* indicates that a alow and progressive change* apparently initiated by heating and accelerated by ultra-violet light* was taking place* In the same manner runs 30, 31 and 36* 37 were a aeries of runs in benzene in which the effects of heating and exposure to ultra-violet light, with and without nitrobenzene, were studied. The results of this series of runs are illustrated in Fig. 16* in which the loss of p-nitrosophenol is plotted against time. Particular care was taken to achieve precise 95 duplication of all conditions except those specified as varying*

Tables XI and XII summarize the results obtained from these re* actions* it was observed that in all the runs, the loss of nitrosophenol was g re a te r when no n itro compound was present th at i t was when nitro** bensene was present* This reverses the behavior observed in most of the earlier runs with p-nitrosodimethylimiline* The difference was consider* ably greater when ultra-violet light was employed, but it was still definitely present when such light was not used} for this reason, if for no other, it seems unlikely that the difference was due to any relative opacity (toward ultra-violet) produced by the presence of nitrobenzene*

There is ample evidence from repeating these reactions under the same conditions that the inhibiting influence exerted by nitrobenzene on the photochemical and thermal decomposition of p-nitrosophenol is at least qualitatively reproducible*

Fig* 16 shows that when p-nitrosophenol underwent either thermal or photochemical decomposition, the relatively rapid decomposition of the nitroso compound during exposure to light and/or heat was followed by a slow but pereeptible continuation of that decomposition for six to eight days thereafter; a decomposition which gradually appears to stop after th a t time* Runs 56-13 show that a trace of nitrobenzene did not exhibit this inhibiting effect to a measurable degree* When more substantial concentrations of the nitrobenzene were used, and were varied, the magnitude of the inhibiting effect was increased by increasing the nitro­ benzene concentration, but it was increased in something less than 4 proportionate degree. This appears to eliminate any explanation which would give the nitrobenzene a "chain-breaker" role, and lessen the likelihood that it has a Catalytic function of any sort*

Comparison of Runs 38-39 with Runs 40*41 indicates a substantial theraal factor accompanying the photochemical factor in promoting the decomposition of p-nitrosophenol, but shows the nitrobenzene exerting essentially the same influence at the higher temperature as at the lower one*

Pig* 17 shews the re s u lts obtained from a run whose purpose m s to determine the manner in which the rate of photochemical decomposition of p-nitrosonhenol varied with time of exposure to ultra-violet light*

It will be observed that a short lag period at the outset was followed by ft period la which the rate of decomposition reached a maximum; after which, as was to be expected, the diminishing p-nitrosophenol concentration of the solution brought about a gradual dimunition in the rate*

It should be emphasised that no high degree of precision can be claimed for the points on this curve* This is particularly true of those in the early part of the run, where two sources of error were at a maximum:

(1) the total loss of nitroso compound was small compared to the recognized range of experimental error; and (2) the difficulty of obtaining a truly characteristic sample without interrupting the run was relatively large, since the photochemical effect Is more or less localized* As the run proceeded both of these sources of error became less significant, so that the la te r points became increasingly reliable* In a l l three runs, run under the same conditions, there was In fact a conspicioue degree of eccentricity in the points representing losses during the first on© or two hours. The general trend was evident In each ease, however* Con­ sidering all three runs, and taking into account the relative ina curacy of the value* obtained In the early parts of them, they may be summarized by the 97 statement that they gave evidence of a lag of fro® one to three hours duration.

the following hypothetical explanation, admittedly incomplete and not established by adequate evidence, but s till in accord with the available observed facts, is advanced tentatively t

Thai thermal and photochemical decomposition of p-nitrosophenol results in tbs £b m at ion of an unidentified compound (X), among other products) that X is capable of reacting with additional p*nitroso-» phenol) and that the inhibiting influence of nitrobenzene results fro® its ability to react with X also, leaving less of the latter available for reaction with the nitroso compound* Applying the hypothesis to the observations, the lag period is, presumably, the period in which the concentration of X is being built up from zero to its maximum) the maximum being a level at ldiich it is being destroyed as fast as it is being formed. The variation in the extent of the inhibiting influence of nitrobenzene, with variation in its concentration (as revealed in Table XX) is in qualitative agreement with this hypothesis, though the quantitative relationship can riot be explained at present*

Acting on the theory that X might be p-iydroxyph®nylhydroxyl-» amine, several attempts were made to prepare this compound, hoping to identify it with one of the ©aapcnents of the photochemical re-* action produets by comparison of absorption spectra, chromatographic characteristics, end perhaps other properties. All attempt® to synthesise it have failed, however) it may be too unstable to permit th e n e c e s s a r y isolation, purification and identification*

However, i f X i s p^hydroxypbenylbydroxylamine, i t s reaction with p-nitrosophenol should give p-p1 -azoxyphenol. This compound was detected among the products of the photochemical decomposition of n P-ftltrosophenol| and was identified by comparing its chromatographic and spectrophotometric charaoteristies to those of a known sample of the same m aterial* PART III * S M !

A study has been made of the decompositions of p-nitrosodlrmthyl**

aniline and of p-Halt roso phenol, under different conditions of light and

temperature, in the presence of nitro ©oaapoundsj and their behavior has been compared to that which they displayed in the absence of nitro compounds*

Under most conditions, the influences exerted by the nitro compounds

were found to be small compared to the spontaneous decompositions of the

nitroso compounds themselves, but several marked exceptions to this were

observed* The photochemical decomposition of p-nitrosophenol in the

presence of nitrobenzene was particularly noteworthy, and was studied

at some length* It was quite unlike the behavior of p~nit ro sodimethyl-

aniline under sladliar conditions •

99 A SSiECTED BIBUGRAPHX

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in flitronitrosonaphtole«

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(34) Hodgson, H. H. and Moore, P. H.

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of Disperaivlty*

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for Chromatography.

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and I n it ia l Voliaae.

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in Crude Cotton-Seed Oil.

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Ueber Dinitrobntane.

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(48) Michael!s, A. and Kotelmann, P.

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J . Chem. S oe., 925# (1895)* (50) Nyga&rd, E. M.

Production of Nitrolic Acids and ? a eudonitroles.

J.SiP. 2,401,268 Key 26, 1946.

(51) Owens, J . S.

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Internal Control Method.

Ind. Eng. Chem., Anal. Ed., 11, 643# (1939)*

(52) Pilot/, 0. and Steinback, H.

Ueber Halogennitrosoverbindun^en dee PlketcK

Cyclohexamethylens und eine Secundare Mitrosoverbinduiigi

B er., 21» 3 1 0 1 , (1902). (53) S c h iff, R.

Ueber das Nitrosotfrymol und desaen Derivate.

Ber., 8, 1500, (1875).

(54) Schmidt, J . and Widmann, K. T.

Uber den &itroflo~bernflteinsaure»diathylester.

Ber., £g, 497, (1909). m

(63) Vermeulaa, M. H.

Sur vuelgues Derives Bela Eeaorcine.

Sec* Trav. Chem,, 2£, 107, (1919)* (64) Weiss, J*

Cta the Theory of Chrpmt^raphy.

J. Chem. Soc., 297-303, (1943)* (65) White, J* W. and Diyden, E. C.

Separation of Alinh&.tic Alcohols by Chromatographic Adsorption o£ Their 3.5-dLnitrobanaaates.

Ind. Eng. Chem,, anal* Ed., SSj 653, (1946). (66) Wilson, J.

A Theory of Chromatography.

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by The Principle ol Chromatographic Adsorption

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Z. Physical Chem., 220, 146, (1934). VITA

Gilton W# Tat© was born in Slaughter, Louisiana on June 11, 1924*

He received his elementary and high school education at Slaughter High

School, graduating in May 1941* In the fall of 1941# he entered

Louisiana State University and remained there until he was called to active duty in the U.S. Army in May, 1943*

After completing his infantry basic training at Camp Fannin,

Texas, he was sent for six months to the University of Alabama where

he studied basic engineering# Upon completion of this course, he was

assigned to an Engineer Petroleum Distribution Unit with which he

served for two years# During that time, he participated in the Hew

Guinea and Luson Campaigns and In the Occupation of Japan# He received

his honorable discharge in February, 1946*

In June, 194& he reentered Louisiana State University and received

the Bachelor of Science degree in Chemistry in May, 1948; continuing

his studies, he received the Master of Science degree in Chemistry in

June, 1950. At the present time, he is working toward a Doctor of

Philosophy degree.

109 Analogous Nitro and Nitroso Compounds Separation, Identification, and Quantitative Estimation

W. R. EDWARDS, Jr. AND CILTON W. TATE Louisiana State University, Baton Rouge, La.

Reprinted from ANALYTICAL CHEMISTRY Vol. 23, Page 826, June 1951 Reprinted from ANALYTICAL CHEMISTRY, Vol. 23, Page 826, June 1951 Copyright 1951 by the American Chemical Society and reprinted by permission of the copyright owner

Analogous Nitro and Nitroso Compounds Separation9 Identification9 and Quantitative Estimation

W. R. EDWARDS, Jr., a n d CILTON W. TATE • Louisiana State University, Baton Rouge, La.

ANY reactions of nitrogenous organic substances, particu­ lent to p-nitrosophenol) from mixtures containing also the di- M larly oxidations, result in the formation of mixtures con­ oxime and the by-products formed during nitrosation and oxima- taining, among other things, analogous nitro and nitroso com­ tion of phenol. Other uses of chromatography in conjunction pounds. Difficulties are encountered when the separation of with spectrophotometry have been described by various authors such coexisting products is attempted by the usual methods. (1, 2, 6, IS). Similarities in solubilities make the use of selective solvents un­ satisfactory, and such circumstances as unsuitable vapor pres­ APPARATUS sures and insufficient stabilities may interfere with distillation A No. 1 chromatographic column (9 X 130 mm.) was employed procedures. These difficulties may reach prohibitive propor­ for most of the separations. It was filled with adsorbent to a tions when the desired products exist in small total quantity, height of 80 mm., using the technique described by Strain (IS). in dilute solution, and in the presence of other substances. The present work describes a method for the separation of such compounds from solution and from each other by chromatogra­ phy; for the partial identification of each by observation of the Oxidations and other reactions of nitrogenous or­ position and color (natural or developed) of its adsorption zone; ganic compounds frequently produce mixtures con­ and for the further identification and quantitative estimation of taining analogous nitro and nitroso compounds, each by spectrophotometry. The method would serve equally whose separation and analysis by other methods are well for analysis of a solution containing only one such compound. in some instances relatively difficult. The chro­ The five pairs of (7-nitro and C-nitroso compounds studied re­ matographic characteristics of five C-nitro com­ sponded well to both chromatographic and spectrophotometric pounds, their C-nitroso analogs, and one iV-nitroso treatments; it seems probable that many similar pairs would do compound were determined. All were recovered the same. Study of one A-nitroso compound indicated a possible effectively from very dilute solutions by this method. extension of the method to mixtures of such related substances Each nitroso compound was much more strongly as nitramines and nitrosamines. The fact that extremely small adsorbed than its nitro analog, a circumstance favor­ quantities of solutes in very dilute solutions were separated and ing accurate separation. Standard spectrophoto­ estimated with at least approximate accuracy under mild condi­ metric absorption curves were constructed, suitable tions gave renewed evidence of the usefulness of such methods for their identification and estimation. The com­ in work with compounds which are relatively unstable when bined chromatographic and spectrophotometric heated or isolated, and particularly in the field of high explosives procedures offer a means of analyzing a solution con­ research. taining minute quantities of a nitro compound and Trueblood and his coworkers {14) have employed similar its nitroso analog, or either one. Specifically, the techniques to advantage in this specialized field. The present method has been applied to five such pairs; it ap­ work was also approached at one point by the papers of Gull- pears probable that it could be extended to others. strom et al. {5), describing the separation and estimation of small It should have special value in work with explosives. amounts of p-benzoquinone monoxime (tautomerically equiva­ VOLUME 2 3, NO. 6, JUNE 1951 827

first portion. It was then washed three times with 10% aqueous 0 "P-NITSOPHENOL sodium carbonate and three times with water, dried over anhy­ drous sodium sulfate, and distilled over sodium metal, the frac­ tion boiling at 65° to 67° being retained for use.

EXPERIMENTAL PROCEDURES The chromatographic characteristics of the individual nitro and nitroso compounds (Table III) were determined as follows:

Table I. Materials * e p-NITKOSOPHlNOl M elting Refer- Point, ( ■ 8.34 A T 310 iy* Name Source ence ° C. Solutes p-Nitrophenol Eastman Kodak Co., Research Laboratory 113 p-Nitrosophenol Synthetic, mtrosation of phe- nol (7) 123-125 2.4-Dinitroresoroinol Synthetic, two-step nitration of resorcinol9 (5,15) 146.5 2.4-DinitrosoresorcinolEastman Kodak Co., Re­ WAVE LENGTH IN search Laboratory 167 s l-Nitro-2-naphthol Synthetic, oxidation of 1- Figure 1. Absorption of p-Nitrophenol and p-Nitroso- nitroso-2-naphthol with ni­ tric acid (4) 102.5 pbenol in Absolute Ethyl Alcohol 1-Nitroso-2-naphthol Eastman Kodak Co., Re­ search Laboratory 109.5 2-Nitro-l-naphthol Synthetic, oxidation of 2-ni- In two specified instances, a No. 2 column (20 X 220 mm.) was troso-l-naphthol with alka­ used. In the preliminary purifications of the nitro and nitroso line hydrogen peroxide (4) 127-128 2-Nitroso-l-naphthol Eastman Kodak Co., Re­ compounds, a No. 4 column (48 X 300 mm.) was employed. search Laboratory 162-163 Extinction coefficients were determined by use of a Beckman 2,2-Dinitropropane Synthetic, oxidation of 2-ni- Model DU spectrophotometer. troso-2-nitropropane with chromic acidc (10) 53 2-Nitroso-2-nitropro- Synthetic, nitrosation of 2- MATERIALS pane nitropropane (11) 75 Diethylnitrosamine Synthetic, nitrosation of di- The solutes obtained or prepared as indicated in Table I were ethylamine (3) 1764 further purified chromatographically immediately before use; Solvents Benzene Merck, reagent grade, thio- about 0.4 gram of material in each run was treated with solvents, phene-free adsorbents (prewashed), and developers identical to those shown Ethyl alcohol (abso­ U. S. Industrial Chemical Co., in Table UL The appropriate zones were eluted with absolute lute) U.S.P. Acetone Merck, reagent grade, redis­ alcohol, and the solvent was removed by evaporation at room tilled and dried temperature. Ether (anhydrous) Mallinckrodt Chemical When Celite was used as a filter aid, the proportions were: 2 Works, reagent grade Petroleum ether Skellysolve Petroleum Co., parts by weight of silicic acid to 1 part of Celite. The adsorbents Skellysolve B * were standardized (Table II) by determination of the R values, Adsorbents with respect to them, of 0.6-mL portions of a 0.01M solutfon of Silicic acid Merck, reagent grade o-nitroaniline in benzene (method of LeRosen,9). Such stand­ Celite Johns-Manville ardization permits conversion of data obtained with one adsorb­ ° 2-Nitroresorcinol formed as intermediate. ent system to other systems. s Decomposed. c Much improved yield obtained by conducting oxidation at 15-16° for Adsorbents were not prewashed, except when this is men­ 24 hours, instead of using elevated temperature described in reference. tioned specifically. In such instances it was accomplished by 4 Boiling point. employing, in succession, 1 volume of acetone, 1 volume of * Purified; see text. ether, and 2 volumes of petroleum ether; “1 volume” is defined as the quantity which would barely wet the entire column, so Table II. Standardization of Adsorbents that its top became dry just as the first liquid reached the bot­ tom. Adsorbent Solution Developer R Value The petroleum ether was purified as follows: Commercial Silicic acid 0.01 M o-nitroaniline in benzene .Benzene 0.374 Silicic acid-Celite 0.01 M o-nitroaniline in benzene Benzene 0.534 petroleum ether B was shaken with several successive portions of Silicic acid-Celite 0.01 M o-nitroaniline in benzene Benzene 0.512 fum ing sulfuric acid, standing overnight in contact with the (prewashed)

Table III. Chromatographic Characteristics of Nitro and Nitroso Compounds Color of Zone Sensitivity Before After (after Compound Solvent Adsorbent Developer R Value streaking streaking9 Streaking), M p-Nitrophenol Benzene Silicic acid and Celite Benzene (96%) 0.378 Colorless Yellow 0.00004 Acetone (4%) p-Nitrosophenol Benzene Silicic acid and Celite Benzene (9®%) 0.222 Colorless Yellow 0.00008 Acetone (4%) Benzene Silicic acid and Celite Benzene (96%) 0.382 Yellow Yellow 0.00008 2.4-Dinitroresorcinol Acetone (4%) Benzene Silicic acid and Celite Benzene (96%) 0.100s Colorless Green-blue* 0.0005 2.4-Dinitrosoresorcinol Acetone (4%) 0.894 Yellow Yellow 0.00004 l-Nitro-2-naphthol Benzene Silicic acid Benzene Silicic acid Benzene 0.284 Red-brown Red-yellow 0.0002 1-Nitroso-2-naphthol Benzene 0.00004 Benzene Silicic acid and Celite Benzene 0.960 Yellow Yellow 2-Nitro-l-naphthol Benzene 0.215 Yellow Yellow 0 .00004 2-Nitroso-l-naphthol Benzene Silicic acid and Celite Petroleum ether Silicic acid Benzene (50%) 0.8504 Colorless Blue® 2,2-Dinitropropane Petroleum ether (50%) 0,0004 Petroleum ether Silicic acid Benzene (50%) 0.416 Blue/ B lue/ 2-Nitroso-2-nitropropane Petroleum ether (50%) Petroleum ether 0,0604 Colorless Diethylnitrosamine Petroleum ether Silicic acid “ Streaked with 6 M NaOH unlees otherwise indicated Except where noted, colors existing before streaking were intensified by streaking.

• St^^d^V diphenySm ine8in H*SO<. Boundaries indef&ite and unreliable. / Coloriessw h e n d?y, color restored by streaking with benzene. 828 ANALYTICAL CHEMISTRY

Preliminary experiments were made to ascertain a combination 6.0 of solvent, adsorbent, and developer which would serve efficiently for the isolation of each compound. Where necessary, the rate of as © ■ I- NITRO- 2* NAPHTH0L movement of an adsorbed zone was increased^ by dilution of the «■ 3.13 AT 330 By* adsorbing silicic acid with Celite, or by dilution of the benzene usually used as the developer with acetone, or both. All initial solutions were 0.01M except three containing solutes of relatively low solubility: p-nitrosophenol (0.0004M), 2,4-dinitrOBoresor- cinol (0.0025 M), and 2-nitroso-2-nitropropane (0.0026 AT). 4.0

A* I-NITR0S0-2-NAPHTH0L- 2,4-DINITAOSORCSORCINOL €■ 3.30 AT 370 "V ( • 12.71 AT 220 m/L 5 3.0

2.0

W A V E L E N Q T H IN ftpI Figure 4. Absorption of l-Nitro-2-naphthol and l-Nitroso-2-naphthol in Absolute Ethyl Alcohol

l- NITROSO-2-NAPHTHOL t s o 2 5 0 > 7 0 910 9 9 0 SIO €■ 13.2 AT 2 6 0 KIN WAVE LENQTH IN nyt X Figure 2. Absorption of 2,4-Dinitrosoresorcinol .in t- * Absolute Ethyl Alcohol 411

* O I-

u o- j 3

z 12 2 4 0 270 260 WAVE LENGTH IN Figure 5. Absorption of l-Nitroso-2-naphthol in Absolute Ethyl Alcohol

Table IV. Recoveries of Nitro and Nitroso Compounds from Solutions 4 0 0 4 2 0 Quantity W A V E L E N Q T H IN my* Concentra­ Chromato­ Size of % Figure 3. .Absorption of 2,4-Dinitroresorcinol in Compound tion, M graphed, Ml. Column Recovc Absolute Ethyl Alcohol p-Nitrophenol 0 .0 1 1 No. 1 97 p-Nitrophenol 0 .01 5 No. 2 98 p-Nitrosophenol 0.00041 1 No. 1 92 One milliliter of a solution of the compound undergoing ex­ p-Nitrosophenol 0.00041 5 N o. 2 98 2,4-Dinitroreaoroinol 0 .01 1 No. 1 94 amination was delivered to the top of the column. As its upper 2,4- D initr os oresor cinol 0 .0025 1 No. 1 88 edge disappeared into the adsorbent, addition of one volume of l-Nitro-2-naphthol 0.01 1 No. 1 94 the developer was begun. The R value of the solute under the l-Nitroso-2-naphthol 0.01 1 No. 1 91 2-Nitro-l-naphthol 0 .0 1 1 No. 1 96 experimental conditions was determined. Streaking agents were 2-Nitroso-l-naphthol 0 .0 1 1 No. 1 93 employed to produce or to intensify zone color. Similar runs 2,2-Dinitropropane 0.005 1 No. 1 88 were then made with increasingly dilute solutions to determine 2-Nitroso-2-nltropropane 0.0025 1 No. 1 79 the sensitivity of the method for each compound—that is, the Diethylnitrosamine 0.01 1 No. 1 85 lowest concentration which would give a dependably visible ° Averages of 3 determinations. Extreme variation, =*»3%, zone. The zones of 2,2-dinitropropane and diethylnitrosamine were colorless, and no streaking agents were discovered which would indicate their boundaries with sufficient precision, though a solution of diphenylamine in sulfuric acid produced a recognizable chemical change or evaporation; some nitroso compounds, in but ill-defined blue shade with the former. The positions of particular, gave altered results after long standing. Normally, these zones, therefore, were determined by systematic spectro- photometric examination of successive portions of the columns. the absorption range between 220 and 310 mp was covered; if a satisfactory absorption maximum was hot found within this Spectrophotometric data for the nitro and nitroso compounds range, measurements were extended to other wave lengths. were obtained from standard solutions in absolute ethyl alcohol, Figures 1 to 9, inclusive, contain curves constructed fromtheBe with readings at 5 mu intervals. The elapsed time between final data by plotting molecular extinction coefficients (e) against purification of each solute and its spectrophotometric measure­ wave lengths. Measurements of standard solutions of different ment was made as short as possible to minimize errors due to concentrations showed that these compounds obeyed Beer’s law VOLUME 2 3, NO. 6, JUNE 1951 829

ing any part of it to become dry, the column was washed with a little more than one volume of petroleum ether to remove any 6* 8-NITRO-l-NAPHTHOL A * 2- NITROSO- 1- NAPHTHOL adsorbed developer. The column was extruded, and the zone * • «.ro a t g«g nvA « • £8.1 A T containing the compound sought was cut out. If the compound was one which gave a colorless zone, two columns were run under identical conditions. One was streaked to develop a color, and the position of the zone was thus determined; the seeond was cut “blind” at the same position, and the material in this second (un­ streaked) column was used for the subsequent spectrophoto-

2«

1.2

10 2,2-DINITROPROPANE s# € « .833 A T 28010/*.

.8

8 9 0 8 6 0 WAVE LENGTH IN *Jt .8 Figure 6. Absorption of 2-Nitro-l-naphthol and 2-Nitroso-l-naphthol in Absolute Ethyl Alcohol

,4

■2

2— NITROSO — 2— N1TROPROPANE

« £- 12,18 AT 290 m jt S JO x 880 8 6 0 £ 7 0 2 9 0 ►z W A V E L E N G T H IN m/i M o Figure 8. Absorption of 2,2-Dinitropropane in X b. u Absolute Ethyl Alcohol o o z o

► .09 X hi DIETHYLNITROSAMINE €• .079 AT 330 m/t A o Io o 2 .07 I- uz 230 2 4 0 280 270 2 8 0 290 900 910 3 WAVE LENOTH IN m/l Hi o Figure 7. Absorption of 2-Nitro8o-2-nitropropane in « Absolute Ethyl Alcohol .05 *- o z

X for dilute solutions; the data could be used, therefore, for quan­ ui titative estimations. For some types of more precise work, spec- trophotometric measurements at shorter intervals should be a bj _ 1 made. O The procedure followed for the identification and estimation of 3 related nitro and nitroso compounds in unknown solutions con­ taining one or both (and possibly other solutes) was as follows: W A V E L E N G T H IN m/t Figure 9. Absorption of Diethylnitrosamine in One milliliter of the solution was chromatographed in the Absolute Ethyl Alcohol manner previously described for the determination of chromato­ graphic characteristics. After developing, and without allow­ metric examination. When analogous nitro and nitroso com­ pounds were both present, the latter was always much more strongly adsorbed, so that no difficulty was experienced in sepa­ Table V. Recoveries of Solutes from Solutions Containing rating the zones. Mixtures of Analogous Nitro and Nitroso Compounds0 Each zone thus isolated was powdered, dried at room tem­ Composition of Solution Recovery!, % perature, put back on the column, and eluted with sufficient ab­ solute ethyl alcohol to dissolve all adsorbed material. The eluent p-Nitrophenol, 0.002 M 9 6.7 91 was diluted suitably, and a significant portion of its spectro­ p-Nitroaophenol, 0,005 M photometric absorption curve was determined. Concentration 2.4-Dinitroresorcinol, 0,005M 2.4-Dinitrosoresorcinol, 0.00125M 85 of the solute was calculated from its extinction coefficient at or near a peak; for this purpose the appropriate wave length speci­ l-Nifcro-2-naphthol, 0.005 M 96 1-Nitroso-2-naplithol, 0.005 M 94 fied in Figures 1 to 9 was selected, representing an actual point of measurement of the standard solution. Identification of the 2-Nitro-l-naphthol, 0.005 M 2-Nitroso-l-naphthol, 0.005 M 90 solute was accomplished in the same process by comparing the position and color of the chromatographic zone, and the shape • Data obtained by chromatographing 1 ml, of each solution on No.1 and dimensions of the spectrophotometric curve, with the corre­ eolnmn. , ^ . . . ! Averages of two or more determinations. sponding characteristics shown by the standard solution of the same compound. 830 ANALYTICAL CHEMISTRY

Because of the relative weakness with which they were ad­ propane and diethylnitrosamine) some further loss is inevitable, sorbed, 2-nitro-l-naphthol and 2,2-dinitropropane formed zones but it should be smaller than such loss when other methods are so near the bottom of the chromatographic column that washing employed. with petroleum ether as described above might have caused ap­ ACKNOWLEDGMENT preciable loss. For these compounds, the chromatographic pro­ The authors express appreciation for the financial support cedure was modified. derived from a contract with the Bureau of Ordnance, Depart­ After developing, the column was extruded without washing. ment of the Navy. They express appreciation, also, for the The zone was cut out, powdered, dried, put back on the Column, friendly advice and cooperation of A. L. LeRosen. and eluted with absolute ether. The ethereal solution was col­ lected in a 25-ml. volumetric flask, and the ether evaporated. LITERATURE CITED The residue was dissolved in absolute ethyl alcohol, without re­ moval from the flask, and subjected to spectrophotometric ex­ (1) Brown, R. A., Emmett, A. D., Ewing, D . T., and Kingsley, amination. G. V., I n d . E n g . Ch e m ., A n a l . E d ., 15, 301 (1943). (2) Dewitt, J. B., and Sullivan, M. X., Ibid., 18, 117 (1946). Tables IV and V show the efficiencies of the method; the former (3) Geuther, A., Ann., 128, 151 (1863). (4) Grandmougin, E., and Michel, O., Ber., 25, 972 (1892). lists recoveries from solutions each of which contained a single (5) Gullstrom, D. N., Burchfield, H. P., and Judy, J, N,,I nd . solute, an'd the latter describes the results obtained with solutions E ng . Chem ., A n a l . E d ., 18, 613 (1946). containing pairs of analogous nitro and nitroso compounds. Re­ (6) Halpern, G. R., Ibid., 18, 621 (1946). covery was only semiquantitative; however, with the possible ex­ (7) Houben, J., “Die Methoden der Organischen Chemie,” 3rd Auflage, Vol. 4, p. 109, Leipzig, Germany, George Thieme ception of 2,2-dinitropropane, it was much superior to parallel 1941. recoveries of the same materials from similar dilute solutions by (8) Kauffmann, H., and DePay, E., Ber., 37, 725 (1904). other methods. Probably a large part of the loss was incurred in (9) LeRosen, A. L., J. Am. Chem. Soc., 64 , 1905 (1942); 67, 1683 transferring the small samples required by use of a No. 1 column. (1945). (10) Meyer, V., and Locher, J.,Ann., 180, 133 (1876). Preliminary work with a No. 2 column, using correspondingly (11) Nygaard, E. M., U. S. Patent 2,401,268 (May 26, 1946). larger samples, substantiates this contention; losses were re­ (12) S m ith , F . H., I n d . E n g . C h e m ., A n a l . E d ., 18, 41 (1946). duced materially, as shown in the first four lines of Table IV. (13) Strain, H. H., Ibid., 14, 245 (1942). Circumstances permitting, it seems probable that the accuracy (14) Trueblood, K. N., Schroeder, W., and coworkers, Office of Scientific Research and Development, OSRD Rept. 5952 of the method could be increased further by the use of still larger (1945). columns and samples, perhaps merely by use of a larger sample (15) Vermeulen, M. H., Rec. trav. chim., 38, 106 (1919). with a No. 1 column. Where the nitro or nitroso compound is R e c e iv e d October 27, 1950. From an M.S. thesis submitted by Cilton W, volatile or unstable (notably in the cases of 2-nitroso-2-nitro- Tate to the graduate school of Louisiana State University, June 1950.

P r in t e d i n U. S. A. EXAMINATION AND THESIS REPORT

Candidate: O il to n ’.T, Tate

Major Field: Ghemistrv

Title of Thesis: , ^ „ a btnay oi oome N itro so Compounds

Approved:

Major Professor and Chairman

Deanjof-fhe Graduate School

EXAMINING COMMITTEE:

1L.E .£

'X ib J .

Date of Examination:

, i n i z- ? ,