Electrolytic Reduction. of Polynuclear

ELECTROLYTIC REDUCTION. OF POLYNUCLEAR

AROMATIC HYDROCARBONS

Henry Routon Harrison

Bachelor of Science

Oklahoma State University

Stillwater, Oklahoma

1964

Submitted to the facultyof·the Graduate College ofthe Oklahoma State University in partial fulfillment of the requirements for the degree of. MASTER. OF SCIENCE July, 1966 ELECTROLYTIC REDUCTION OF POLYNUCLEAR

AROMATIC HYDROCARBONS 1;

Thesis Approved:

~~Thesis Adviser

the Graduate College

ii PREFACE

I wish· to express my gratitude to Dr{ E. j. Eisenbraun for his invaluable guidance and counsel during the course"of my graduate work.

The auth~r is grateful to Dr. Paul Arthur for his advice concerning electrolytic processes. Thanks are also due toDr.·P. W, K, Flanagan and Mr~ M. C. Hamming of the· analytical division of the Continental Oil

Company, Ponca City, Oklahoma, for the instrutnentalanalyses. · I wish to thank Mr.; R, C. Bansal for his help and for authentic samples from his collection. I wish to express appreciation to;my wife, Patricia, for·her·patience,and understanding.

I also wish to thank· the.American Petroleum Institute for financial aid in the form a research assistantship throughR.eseareh Project SSA at Oklahoma.State University.

iii TABLE OF CONTENTS

Chapter Page

I. INTRODUCTION. 1

II. ijISTORICAL ••• 2 III. gESULTS AND DISCUSSION; • . . 7

IV. jjl:XPERIMENTAL. • • • ,; • I • - • • • • • • • • • • • 20

Purificatiort of Ethylamine • • • • • • 21 Preparative Electrolytic Reduction Apparatus • • • • . 21 Preparative lleduction' of. Naphth~lene • • • • 24 Identification of• the Products .. from Electrolytic Reduction of Naphthalene .. • • • • • • • • 27 Small Reduction Cell • • • ·• • • • . • 27 Reduction of 2,3-Dimethylnaphtha).ene • 29

I ' B IBL IOGRAFHY • • ·~ .• • • • • •O • • • e e . e • e • 31

iv LIST OF TABLES

Table :Page

I. Electrolytic Reduction of Selected· Naphthalenea. Using Ethylamine_ a.nd Propyla.mine Solvent, ••• 8 ' . . . II~ '.Electrolytic ~educti9ns Using the Small Reduction Apparatus...... 9

III. Preparative Reduction.of Naphthalene with Ethylamine Solvent·.••••••• 10

IV. Preparative Reduction of Acenaphthalene with Et;hylamine . . .. · ...... 11

LIST OF FIGURES

Figure Page

1. Mechanism for Electrolytic .Reduction ••.•••. 6

2. Naphthalene Reduction ProductsiMeas1,1red at 24-Hour Time Intervals, Part a •••.•... • ••••. 17

3. Naphthalene Reduction Products Measured at 24~Hour Time Intervals, Part b ..•••.•..••.• 18

v 4

LIST OF ILLUSTRATIONS

Plate Pa~e

I. Preparative Electrolytic Reduction Apparatus . 22

II, Gas Chre>matogram of Products from Electrolytic Reduction of Naphthalene ...... 25

III. Gas Chromatogram of Products from Electrolytic Reduction of Acenaphthalene .•... 26

IV. Small·· Electrolytic Reduction Apparatus . 28

v. Ga~ Chromatogram of Products from Electrolytic Reduction of 2,3-Dimethylnaphthalene .... 30

vi CHAPTER I

INTRO DUCT ION

This .study was undertaken in connection with the American Petro leum Institute's Standard Samples Program in an attempt to find new routes for synthesis of certain hydrocarbons which are difficult to prepare through conventional methods. An important aspect of this synthetic method is to gain a better understanding of electrolytic reduction. Electrolytic reduction of polynucleararomatic hydro carbons using platinum metal electrodes, alkali metal salts as elec trolytes, and low-molecular-weight amines as solvents has not been extensively studied. Consequently, there is little known about the effects produced by varying the structure of the amine solvent, the structure of the aromatic hydrocarbon, the temperature of the reaction and the nature and concentration of the alkali metal salt used as electrolyte. It has been suggested1 that this electrolytic process is related to metal-amine reductions and accordingly, the mechanism devel oped to explain the Birch reduction and related reactions2 may be uti lized in explaining electrolytic reduction.

The purpose of this research was to study the effects produced by varying the reaction parameters and through analysis of products to arrive at an explanation of how the various hydrocarbon reduction products are formed.

1 CHAl>TER II

HISTORICAL

The first electrolytic reduction of an aromatic ring was reported in 1906. This was accomplished by Mettler, 3 who reduced benzoic acid to cyclohexene carboxylic acid using a mercury cathode and aqueous potassium hydroxide as the electrolyte and solvent.

Since that time, there have been a few investigations into the polarographic reduction of benzene, 4 naphthalene, 5 and phenanthrene6 at a dropping mercury electrode, i.e. a micro-electrode, but there have been only a few studies of reduction of aromatic nucleii at macro-electrodes. The literature review for this thesis will be concerned primarily with reductions at macro-electrodes. Reaction products from micro- and macro-electrodes have been shown to differ due to charge density and conceptration of the reactive species in the vicinity of the electrodes. 7

Benzoic acid in aqueous sulfuric acid solution has also been reduced with platinized platinum electrodes prepared by depositing platinum from a solution of chloroplatinic acid onto smooth platinum.

It had been shown that smooth platinum electrodes were not effective in this solvent. 8

2 3

Polarographic reduction of naphthalene has been u1:1ed to show the electrolytic. reduction mechanism involves a two-electron transfet proceeding, via 1,4-addition. 9 The only report of electrolytic reduction of a naphthalene nucl'eus at macro-electrodes is that of 2- methoxy- and 1.,2, 7~trimethoxynaphthalene to the corresponding enol ether. 10 A lead cathode and aqueous sulfuric acid-dioxane solvent was used.

CFl3b OCH 3 ------~t>

Coupling products usually result from electrolyt;i.c reduct;i.on of heterocyclic aromatic amines in aqueous sulfuric acid using a lead cathode. 11

@ -----....it> + N

However;. the electrolytic reduct:lpn of indole results in hydro genation of the heterocyclic ring:12

@CJ -----t> N I I H H

Lyons 13 reported reduction potentials of -1.89 and -2.88 V for 4

naphthalene and benzene respectively. These data may be used to explain the ease of reduction of naphthalene to tetralin and the resistance of tetralin to further reduction in a sodium-ammonia system.

Until 1946, all electrolytic reductions were carried out in water, aq4eous ethanol, or aqueous-dioxane solvents, using electrodes of platinized platinum, mercury, or lead and a sulfuric acid electrolyte.

In 1946, Birch14 reported ~lectrolytic reduction of 3-methylanisole to 2,5-dihydro-3-methylanisole using liquid ammonia as solvent, sodium ethoxide as electrolyte, and a smooth copper cathode at

-40°.

There have been two additional investigations into the electrolytic reduction of a benzenoid hydrocarbon. 15 , 16 One investigator was able to obtain selective reduction. 1J Selective reduction was also observed in Mettler's original work3 in which phthalic acid was reduced at a mercury cathode. The use of aqueous sulfuric acid electrolyte gave 1,2,3,4-tetrahydrophthalic acid, while an aqueous potassium hydroxide electrolyte gave 1,2-dihydrophthalic acid.

------[> 5

C02H @/ C0 2H-----!> (X '-co2H 02H

Benkeser andKaiser15 reported selective reduction of benzene and alkyl-substituted benzenes using methylamine solvent, lithium chloride electrolyte and a smooth platinum cathode. By separating the anode and cathode compartments, 1,2,3,4-tetrahydro derivatives were obtaine~

However, dihydro products were reported when the electrodes were not placed in separate compartments.

Separated t> 0 ~~~"--~~~~~~Compartments 0 0 0 Reduction to tetrahydro products when separate cell compartments were used was attributed to an excess of lithium ~ethylamide in the cathode compartment, 17 since it has been shown that excess lithium alkylamide will isomerize non-conjugated cyclic dienes to conjugated dienes. These conjugated dienes are then subject to further reduction by the lithium-amine system.

Sternberg16 et al. reported no selectivity during electrolytic reduction using compartmented electrodes; however, in this case, a graphite cathode, ethylenediamine solvent and tetra-_g_-butylammonium- iodide electrolyte vide ante were used. The divider in this case was a sintered glass membrane, whereas Benkeser and Kaiser used an as b es t os d1v1. "d er. 15 6

The multistep mechanism of Krapcho and Bothner-By1 may be used as modified by Sternberg et al. as shown in Fig. 1 to explain the reduction of aromatic hydrocarbons during electrolysis.

.+ e ------!> L1 ••• e

.+ + Ll. • • • e ---!>,

H 1 H

+ •

Figure 1. Mechanism for Electrolytic Reduction

aKrapcho and Bothner-By1 originally suggested BH = CzH50H. b Sternberg, Markby, and Wender 16 suggested the amine solvent func- tions as BH. CHAPTER III

RESULTS AND DISCUSSION

Electrolytic reduction of aromatic hydrocarbons using lithium- chloride as electrolyte and a low-molecular-weight amine as solvent has been restricted to benzenoid hydrocarbons.15, 16 It was felt that extension of this reduction system to polynuclear aromatic hydrocarbons would allow synthesis of unsaturated hydrocarbons which are ordinarily not available through conventional routes. Thus, electrolytic reduction could be a step in the partial reduction of aromatic hydrocarbons to cyclic olefins. Since benzenoid hydrocarbons can only be catalytically hydrogenated under high pressure and at ele- vated temperatures, electrolytic reduction is an attractive approach toward destruction of the ring aromaticity because low temperatures and atmospheric pressure are generally used. Other manipulations would be feasible once the pi system is disrupted.

Before applying electrolytic reduction to polynuclear aromatic " hydrocarbons, it was felt that a better understanding of theparameters affecting the reaction pathways was necessary. These parameters are the nature of the electrode, temperature, concentration of metal salt, structure of amine, and structure of the hydrocarbon. The results of our studies are reported in Tables I, II, III, and IV.

The composition of these reaction products was determined through the use of gas chromatography, NMR, and mass spectroscopy analyses. In

7 TABLE I

ELECTROLYTIC REDUCTION OF SELECTED NAPHTHALENES USING ETHYLAMINE AND PROPYLAMINE SOLVENT

Distribution of Hydrocarbons. I -Recovered -~-~! Starting Starting Material Solvent Material,% Structure of Reduced Hydrocarbons

Unknown mixture of ·hexa 1-Methyl Ethyl 1 C@ (@ @O hydro and octahydro naphthalene amine products, 4 peaks 1 (61%) i (10%) -~ (8%) 20%

1-Methyl Ethyl 28 (32%) (10%) (4%) Unknown mixture of dihydro naphthalene amine products, 5 peaks 26%

Unknown mixture of hexa 2-Methyl- Ethyl 1 ocr Osr· O§r@:CY hydro products, 2 peaks naphthalene amine .§.. (45%) I (19%) ~ (10%) ~ (7%) 18%

2-Methyl- Propyl 15 (33%) (16%) (3%) (30%) Unknown compound. Possi naphthalene amine bly a dihydro product 2% 2,6-Dimethyl- Ethyl 0 )§:CY ~ Unknown compound. Passi naphthalene amine 2CY ~ bly a hexahydro product !.Q (61%) 11 (10%) 12 (4%) 25% 2,6-Dimethyl- Propyl 32 (20%) (48%) naphthalene amine

The electrolyses were carried out at the boiling point of the solvents (17° and 49°) for 20 hours. 00 TABLE II

ELECTROLYTIC REDUCTIONS USING THE SMALL REDUCTION APPARATUSa

Total Distribution of Hydrocarbons Yield of I Recovered I Starting Hydrocarbon Starting Material Products,% Material,% Structure of Hydrocarbons

Naphthalene 88 6 @() @O 00 0() 00 2 (11%) 13 (37%) 14 (11%) 15 (33%) 16 (2%)

Unknown mix 2,3-Dimethyl-b 90 7 ture of hexa naphthalene @CC (@(·C@: es:cx hydro & octa 17 (1%) 18 (3%) 19 (48%) 20 (13%) hydro products, 5 peaks 23%

aThe electrolyses were carried out in ethylamine solvent for 20 hrs. bTrace quantities of ~ were isolated. "" TABLE UI

PREPARATIVE REDUCTION O:F NAPHTHALENE WITH ETHYLAMINE SOLVENT

Reaction . Time (i@0 w~ O)a @O (Hours) ~-J 00 0:) 00 1 2 13 28 14 15 16 % % % % % % %

24 63 28 4 1 2 2 >1

48 63 28 4 1 2 2 >l

72 33 42 6 7 5 5 2

96 1 73 0 3 13 6 4

120 1 65 0 4 18 7 7

aT entat1ve. structure assignment.

f-' 0 TABLE IV

PREPARATIVE REDUCTION OF ACENAPHTHALENE WITH ETHYLAMINE a

00 ~ cw @) @() 00 (X) 25 (21%) 26 (19%) 27 (3%) ll (0%) 22 (4%) 23 (50%) 24 (2%) ......

aAfter 60 hours reaction time

...... 12

the usual procedure for gas chromatography' analysis, a chromatogram was first obtained for the en.tire reaction mixture; then the reaction <:f . mixture was enriched with an: aut.henti.~.- sample of a compound thought to be present among the reaction products. The analysis was then repeated using the .enriched mixture. If any component of the reaction mixture corresponded to the authentic sample, then its peak intensity increased. In some cases in which authenti_c samples were not available, preparative gas chromatography was used for separation and purification of samples for identification through use of other instruments.

The gas chromatography purification was facilitated by use of flow programming. When flow progrannning is used, all gas flow is stopped and a sample is injected onto the column. Flow is resumed and increased at a linear rate until maximum flow is obtained. This linear increase in flow causes improved separation of the reaction mixture. An additional advantage is the .increased ease of large sample injection when there is no back pressure on the column.

When 1-methylnaphthalene was reduced in the presence of ethylamine solvent, there was obtained 61% of 3 and 8% of 5 as shown in

Table I; this is a ratio of 3/5 = 7.6/1. The use of propylamine as the solvent gives .a ratio of }./~ = · 8/1.

In the reduction of 2-methylnaphthalene' with ethylamjne solvent,

' there was obtained 45% of _?_ and ;I.9% of 2; this is a ratio of ~./l = 2.4/1. When the solvent was changed to propylamine, the ratio was

6/7 = 2.1/1.

From these data, it is seen that changing the solvent does not appreciably change the reduction product ratio for the tetralins. 13

However, the yield of tetralins is substantially less when propylamine is usedsince 28% starting material is recovered when !-methylnaphthalene was reduced. Similarly, 15% starting material was recov-

ered from the reaction with 2-methylnaphthalene and 32% starting material was rec.overed from reduction of 2,6-dimethylnaphthalene, whereas the starting hydrocarbon was essentially consumed when ethyl amine was used. ·rt is our conclusion that propylamine is a less effective reducing agent. When ethylenediamine at 50° was used, con- siderable tar was encountered and no useful product was isolated. An attempt was made to carry out an electrolytic reduction in hexamethyl- enimine solvent at 50°, but no reaction took place since the lithium chloride electrolyte was insoluble, and consequently, there was no current flow. Our attempt to substitute sodium chloride for lithium chloride in ethylamine solvent failed due to the insolubility of sodium chloride.

Orie attempt was made to use sodium tnetal as a source of sodium cations and amide ion as a source of anions to.cause transport pf current: Na' ----1>1 e

Howeyer, this approach was not successful and will require modi fication of the electrolysis apparatus since particles of free float ing sodium metal caused a short circuit across the electrodes and greatly increased the explosion and fire hazard. 14

If temperature alone is an important factor in electrolytic reduction, greaterreduction should be observed when propylamine is used. The Qpposite is true as may be seen in Table I.

In one sense, the use of propylamine is more selective in its reduction than ethylamine: if a tetrahydronaphthalene is desired, then propylamine would be the preferred solvent. However, if more extensive reduction is sought, then ethylamine would be the better solvent choice.

Much of this inequality of reduction product formation may be attributed, as previously pointed out, to differences in solubility of lithium chloride in these solvents. The insolubilities of many metal salts (sodium chloride, potassium chloride, calcium chloride, lithium carbonate, etc.) in low-molecular-weight amines prohibit their use in electrolytic reductions.

The role of metal salt in electrolytic reduction is not fully understood. Sternberg, Markby, and Wenderl 6 suggested that the elec tron involved in electrolytic reduction is transferred from the elec trode to the solution, becomes solvated and stabilized by the metal cation and is then transferred to the hydrocarbon to form a radical anion as shown in Fig. I. Krapcho and Bothner-By1 had suggested essentially the same mechanism. Both research groups concluded that the electron is not directly transferred from electrode to hydro carbon. This was substantiated by polarographic studies16 with tetralin, and tetralin in the presence of lithium chloride-ethylene diamine. It has been suggested that lithium metal is formed from the cation during electrolytic reduction at the cathode16 and the metal 15 cation. Since it has long been recognized that a solvated electron19 and solvated cation20 play an important role in these reactions, it is entirely possible that the oxidation and reduction reactions take place in solution rather than at electrode interface. This overall process from electrons at the cathode surface to reduced hydrocarbon may be rationalized as follows:

LiCl + Added electrolyte +

e + From cathode

@Q H H

A possible objection to this explanation would be that lithium

metal may be expected to accumulate. However, the reversible conver-

sion of lithium metal to cation is favored by utilization of electrons

in the reduction of hydrocarbons.

It has been our custom to occasionally reverse the potential of 16 the electrodes and when this is done, bits of white material flake away.from the electrode.which had been the cathode. It is our belief that this white material is lithium ethylamide since it is hard and brittle and burns when exposed to water. It is also possible that this material is lithium metal or a combination of these.

The metal salt-hydrocarbon molar ratios appear to play an important role in the rate of the electrolytic reduction reaction (Table II and III~ Fig. 2). In the reduction of naphthalene in the small electrolytic reduction apparatus, the molar ratio of lithium chloride to naphthalene was 3,3:1. After 20 hours of reaction time, only 6% of the starting material had not reacted (Table Ill. When naphthalene was reduced in the preparative electrolyt,ic reduction apparatus, the .. · initial lithium chloride-naphthalene molar ratio was,1:1. After reacting for 24 hours, there was 63% of the naphthalene remaining

(Table III). Additional lithium chloride was added at the end of 48 hours of reaction as it was apparent no further reduction had occurred between the 24th to 48th hour (Fig. 2). This additional lithium chloride changed the lithium chloride~naphthalene molar ratio to 2.4:1.

In the 48 hours of reaction time following this molar ratio increase, an additional 62% of naphthalene was consumed.

One can infer from the curves in Fig. 2 that 1,4-dihydronaphthalene is the initial reaction product and is.more stable to further reduction than any of the succeeding reaction products. 1,4-Dihydro- naphthalene(~ may react by isomerization to 1,2-dihydronaphthalene and subsequent reduction to tetralin or by reduction to isotetralin.

That both of thesepathways are utilized is evidenced by the presence of both 1,2-dihydronaphthalene (13) and isotetralin (28) in the 17

Figure 2. Naphthalene Reduction Products Measured at 24-Hour Time Intervals, Part a 18

1 Q 1-1-+-+---+-+-+-+-t-1--+-+-+-+-t--+-i- - -~•- . ~ - - -hl-1-+-1--1-++_4_-4--+~-l-~~- FJ_H-i ~:;: ~ ~ . ~:" v==1I =

l-l---l-t-l---1-1-+-l-+f++-l-+--l-l-1-+-+-+-++ I -l-l-l-+~l-l-+-l-+-+-+-+-+-+-1-- --f- •-t-f- I- -H-.,, ~ L""ts-"'· .... -l-1-i-f-1-i-1-+-l-1-1-+--i--,:_'~~~=r:i.--: -~. ·--·-·:=:::?=1~= ~fi·='=: :=:= )~i~~G~~

i:: ~. .µ Cl! k .µ i:: Q) cJ i:: 0 u .µ § cJ k Q) P-r

0 24 48 72 96 120 Time (Hrs.)

Figure 3. Naphthalene Reduction Products Measured at 24-Hour Time Intervals, Part b 19

reaction mixture. The former i.s only observed in the early stages. @QH

· H H 00

It is believed that the rate-determining step in the reduction of naphthalene to tetralin is the formation of 1,2-dihydronaphthalene.

It is not apparent at this time whether hexahydronaphthalene is formed from tetralin or isotetralin.

From these studies, it may be concluded that electrolytic reduc-

tion of polynuclear hydrocarbons can be used to obtain cyclic olefins.

The degree of saturation in the products is determined largely by the

length of reaction time since a stepwise process·i,s probably involved. CHAPTER IV

EXPERIMENTAL

Nuclear magnetic resonance spectra were obtained with a Varian

HR-60 spectrometer, using tetramethyl silane as an internal standard

(o = O). Mass spectra were obtained with a Consolidated Electronics

Corporation Model 21-103C mass spectrometer. All temperatures are in degrees centigrade. An F and MModel 700 gas chromatography apparatus equipped with a termal conductivity detector was used for the analyses and preparative separations. With the exception of the reduction pro ducts from 1-methylnaphthalene, all hydrocarbons were satisfactorily separated and analyzed on a Carbowax 20 M column (25% on acid washed

Chromosorb W, 10' x 1/4"; helium flow 40 cc/min) operating at 190°.

The reduction products from 1-methylnaphthalene were best resolved on a LAC 886 column (25% on acid washed Chromosorb W, gas flow 40 cc/min) operating at 190°.

Gas chromatography analyses of. all starting materials showed greater than 99% purity. The identity of many of·the reduction products were determined by successive enrichment of reaction.mixtures with authen tic samples and observing the expected increase. in a given peak intensity.

Selected steam distilled reduction products from preparative reductions of naphthalene and acenaphthalenewere purified by preparative gas chromatography (Carbowax 20 M, 25% on base .washed Chromosorb W,

20 21

10' x 3/8", 180°,. he1iuII! flow. programmed from O to. 200 ml/min). I . . . Collection of naphthalene reduction products requires cooling the traps in ice water, whereas collection of acenaphthalene reduction proqucts necessitates heati:ngthe· tra:psto prevent. formation of an aero soi. The. chromatogram· is · pres.ented in Fig. 4.

Purification of Ethylamine. Ethylamine (bp 15")as drawn directly from thiametal cyclinder containscoiloidal iron. Since iron would be exp_ecteq to foul the electrodes, iron free· amine was desired. The cylindet containing; the amine was connected· by rubber tubing to a 2-1. , two-neckeq flask containing sodium hydroxid~ pellets. This flask served a:s,a distillation flask. A 6 11 Vigreux.column, surmounted by a distilb.tion 1)..ead with attached condenser. artd receiver was fitted to

.the distillation flask. A soda lime drying· tµbe at the exit vent pro- tected· tl).eaminefrom atmospheric gasses.

Preparative Electrolytic· Redtictioa Appar-atus.~ .. The,.elect-r-olytic reduction vessel consisted of a glass cylinder (15 cm wide x 29 cm high) with a :j:lat ground lip (1 cm rim width).and a matching cover having two

'§ 24/4Q outer joints equidistance around the top and one'§ 34/45 outer joint in the middle. The cylinder and top were held together by means of a steel clatp.p as shown in Plate I. A Teflon gasket was used to in- sure a tight s~al and prevent loss of amine.

One of the '§ 24/40 joints was fitted with: a high. capacity reflux condenser equipped. with a soda-lime· tube,. the s.econd '§ 24/40 joint was stoppered and .used to add chemicals or withdraw samples.

The'§ 34/45 center joint wasused as a portfor the sandwich of three platinum electrodes·whichwere suspended·on 18 gauge platinum 22

Preparative Electrolytic Reduction Apparatus

Teflon ·~ gasket---'=a.J.l

Chimney

--1-t-t--;-~·Electrode

-- -~ --Magnetic Bar

Plate I 23

wire. To obtain a sealed system, the electrode wires were passed through a Teflon thermometer adapter which in turn was sealed with

Silastic silicone rubber sealant.

Agitation of the solution being electrolyzed was accomplished by a magnetic stirring bar at the botton of the flask and the use of a chimney surrounding the electrodes. The chimneywith perforations at the bottom served as an efficient pump by directing the upward flow of warmed and partially vaporized amine solvent. Fr.esh amine solvent and hydrocarbon automatically entered the bottom of the chimney to complete the pumping cycle. The chimney also served as a baffle to prevent marbles from coming in contact with the electrodes. The marbles were added as an aid toward regulation of solvent volumes21 • In some cases it was desirable to alter the volume of solvent and hydrocarbon. The addition of marbles to fill the void arid provide complete coverage of electrodes served admirably. Thus the need for a variety of vessel sizes was avoided.

The electrodes consisted of three platinum sheets (2" x 6" x 0.004").

These were separated by Teflon rods and spacers to a distance of 14 mm.

The outer electrodes of the sandwich were joined with 18 gauge platinum wire which in turn was connected to the lead wire. The inner electrode was formed by connecting the second 18 gauge lead wire to the center platinum sheet. The center lead was sheathed in a Teflon tube to pre vent electrical contact.

The heat from the electrolysis was dissipated by circulating chilled water around the outside of the reaction flask. The direct current electrical circuit for the electrodes incorporated a double-pole, 24 double-throw switch and a 0-5. amp. aµuneter.

Preparative Reduction of ~aphthalene. The reaetion.vessel was charged with 1800 nil ethylamiti.e, the vessel contents were cooled to

5°, and 42 g (1. 0 mole) of lithium chloride were added slowly from an

Erlenmeyer flask.by means of a Gooch tube •. Slow addition was necessary .... due to heat of .solution. After all lithium·chloride had been added and dissolved, 128 g (1. 0 mole) of naphth~lene were added to the solut:f,on.

Electrolysis was. started at 15 volts and 0.5 amperes. After 48 hours,

58 g (1. 38 moles) of lithium chloride were added. since the reduction had virtually ceased during the 24 to. 48 hour period.. After addition of lithium chloride the current r.ose to 3. ·al\lps. Samples· for gas chromatography analysis were withdrawn.. every 24 hours, At the end of 120 hours~ 98% .of .the naphthalene had been. reduced~ .. These. results are shown in Table III.

At the completion of the·electrolysis, a distillation head with I attached condenser and receiving flask was· fitted·. to .the- reaction vessel and the major portion of the amine solvent was distilled. The reaction product was poured onto ice, acidified with c:oncentrated hydrochloric acid arid extracted-with three 200 ml portions. of.ether. The extract was dried over anhydrous sodium sulfate, filteredand the ether removed by distillation. The resulting dark colored viscous oil weighed 112 g.

This oil was steam distilled, the steam distil.late was extracted with ether, dried over anhydrous sodium sulfate; filtered. and distilled.

The colorless concentrated .oil: weighed 85.4 g. This oil was separated by preparative·gas chromatography vide ante to obtain pure samples of the individual reaction product components for NMR and mass spectroscopy Gas Chromatogram of Products from Electrolytic Reduction of Naphthalene - ----v-;-··-··--·-I ---i:--- ..... ~

Plate II N v, 1 l, ·-····-~i 111 1111[1ffi')~,;~-: JIf ~· ~ 1 1; ~r~~ fI r ru 11 TI • l 1 - __ I L.J ri.J _ ~. i, I ~-)~- -~ LJ _LJ_ I JJ1( JJ. .· -r·,-i :i± - - 1 1 11 1 r'"j\: .._.: 1, D I;~ . ~ ~ ~ rr 1 I I I 11 I 1-.L f: .' !' 1 ~" ...1.Y . · ~ 1 oo 90 l~\ ao. I; !10 I 60 so 140 30 20 10 1111111<

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9Z 27

studies.

The steam distillation pot residue was extracted with ether, the

ether solution was dried over anhydrous sodium sulfate,, filtered and

· the ether was then removed by evaporation. The dark colored residue

weighed 20 g and on distillation yielded 8 g of colorless viscous oil.

Acenaptlthalene was also reduced in the preparative electroiytic

reductio~ apparatus. The reduction products are shown in Table IV.

Identification of·theProductsfrom Electrolytic Reduction of

Naphthalene. .The structures of ~ ~, and 14 were assigned on the

basis of comparison with authentic sainples in gas chromatography analysis.

The structures of 15 and 16 were assigned on the basis of their ..,...,, -- . mass and NMR spectra.

The mass spectrum of 15 showed a parent ion peak at m/e = 134 and

the NMR spectrum showed adsorption at 8 = 1.78 (4H, two equivalent

methylene groups, multiplet); 1.84 (4H, protons allylic to 1 double bond,

doublet); 2.75 (4H, protons allylic to 2 double bonds, singlet); 5.62

(2H, vinylic protons, singlet).

The mass spectrum of 16..;..., showed a parent ion peak m/e = 136 and the

t-.lMR spectrum showed adsorption at 1. 67 ·· (BR, four equivalent methylene

groups, multi~let); 1.84 (SH, allylic protons, doublet).

Similar studies wereused·to establish the, structures of the pro-

ducts obtained from the electrolytic reduction of'acenaphthalene. These

results are presented in Table IV.

Small Reduction Cell. This apparatus was used for runs of 0.05

moles hydrocarbon'and consisted of a 200 ml three-necked round bottomed

flask fitted with a high capacityreflux condenser, a polyethylene 28

Small Electrolytic Reduction Apparatus

\ \ I . \. I I I t~} t Electrodes

Plate·IV 29

stopper·. i~ the middle neck· and a glass stopper· in one of the side necks · through which· chemicals were : added and.c sam.pJ..e,s.c were· removed, Stirring · was accomplished by a magnetic bar. This• flask,·. in contrast to the preparative·:reduction apparatus; was·nptcooled·in a.water bath.since the cond,enser- cooling ·capacity·was suffieient!'.torecondense vaporized amine solvent.

The electrode assembly consisted·· of two, platinum sheets (2 cm x

4 cm x 0.004") spot· we],ded to an 18 gauge platinum wire·, The electrodes were separated by.two 4 mm Teflon spacers., The lead wires from the . . : electrodeswere fed throughtb~polyethyiene':cap·and sealed in place by

Silastic silacone.rubber sealant, The·electricalcircuit was the same as that used with the preparative reduction apparatus.

Reqµ.,ct:Loti. of·, 2 i .3-Dimethylnaphthalene., , The small, react ii.on flask. was charged with 150 ml. ethyl am.ine and 7-. 2. g:· (0.17 moles) of lithium chloride were added slowly through a Gooch tube from ari Erlenmeyer flask, ·After the lithium chloride· disolved,; 7. 9 g (O. 05 mole) of

2,3-dimethylnaphthalene were added and'electrolysis initiated. The reaction was tun at'30 v; and 0.8 ~mperes for 20 hours. At the end of this time, the amine solvent was distilled and the resulting viscous residue poured onto ice. The solution was then acidified with concentrated hydrochloric acid and .extracted with three 50 ml portions of ether. The ether solutionwas·tli.en·dried·over anhydrous.sodium sulfate, filtered and then' removed by distillatic,n .to give 7 .1 g of reduction products. Gas chromatography.analysis revealed 10 components in the reductionmixttire. This chromatogram is'Shown in Plate·V, 30 . BIBLIOGRAPHY

1. A. P. Krapcho and A. A. Bothrier,-By, J. Am. Chem. S<;>c. , 81, 3658

(1959) 0

2. w. Ruckel and, H. Bertschneider,; Ann., 540, 157 (1939).

3. c. Mettler, Ber., 12., 2934 (1906). 4. F. Fichter and. C, Simon, Helv, Chim. acta., 11., 1219 (1934).

5. s. Wawzonek and H. Laitnen, J. A1t1. Chem .•. Soc .• , 64, 2365 (1942).

6. S. Wawzonek and D. Wearring, J. Am. Chem. Soc., 81, 2067 (1959).

7. E. Baur and· E. Muller, Z .• Electrochem •. angew~ phisik., 34, 98 (1928).

8. W. B. Bancroft and A. B. George, Trans. Am. Electroche,:n. Soc., 21..., 399 (1930).

9. C. B. Wooster and F. B .. Smith,J. Am. Chem.Soc., .21, 179 (1931).

10. G.B. Diamond and M. D. Soffer, J. Am. Chem. Soc .. , 74, 4126 (1952).

11. B. Emmert, Ber., ~' 1716 (1913).

12. 0. Carrasco, Gazz ~ Chem-, Ital. , 38 [ 2] , 301 · (1907) •

13. L. E. Lyons, Nature, 166; 193 (1950).

14. A. J.; Birc:h, Nature,, 158, 60 (1946).

15. R. A. Benkeser and E. M. Kaiser,, J. Am •. Chem; Soc. 85,. 2858 (1963).

16. H. W. Sternberg, -R. Markby, and I. Wend.er, J, Eleetrochem. Soc., 110, 425 (1963).

17. R.·A. Benkeser, E. M. Kaiser, and R. F .• Lambert, J, Am. Chem. Soc., .§..§_, 5272 (1964).

18. R. A. Benkeser, M. L. Burrows, J. J. Hazdra, and E. M. Kaiser, J. Org. Chem., ~' 2858 (1963).

31 32

19. N. w. Taylor and G. N. Lewis, J. Am. Chem. Soc., 48, 845 (1926).

20. G. E. Gibson and T. E. Phipp, J. Am. Chem. Soc., 48, 312 (1926).

· 2L Aesop,"TheRaven and the,.Pitcher,". ca. 60Q B.C. VITA

Henry Routon Harrison

Candidate for the Degree of

Master of Science.

Thesis: ELECTROLYTIC REDUCTION OF POLYNUCL~RAROMATIC HYDROCARBONS

Major Field: Chemistry

Biogtaphical:

Personal Data: Born in .Ma.dill, Qklah9111,a, June. 20, 1936, the son of Henry J.. and Mary> E. Harrison~

Education: . Graduated from Stilwell High School, Stilwell, Oklahoma, in 1954; received·Bachelor.:of-Scienee degree from the Oklahoma State University, with a·major. in Chemistry, in May, 1964; completed requirements for-the Master of Science degree in July, 1966. ·

Professional Experience:·· American Petroleum Institute Graduate Research Assistant, June, 1964 - July, 1966.

Membership in Professional Societies:· Member of Alpha Chi Sigma and Phi Lambda Upsilon.