The Use of Liquid Phase Oxidation for the Preparation of Nuclearly Substituted Styrenes. III. p-Vinylbenzyl Acetate

.lug., 1947 PREPARATION ~ V I N Y L B E N Z Y L OF ACETATE [CONTRIBWfION FROM THE CENTRAL RESEARCH DEPARTMENT, MONSANTO CHEMICAL 1905 COMPANY ] The Use of Liquid Phase Oxidation for the Preparation of Nuclearly Substituted 1. Styrenes. 1 1 p-Vinylbenzyl Acetate BY WILLIAM EMERSON, S. JOSEF W. HEYD, VICTOR LUCAS, E. WARREN LYNESS, I. GRAFTON . OWENS R AND ROBERT W. SHORTRIDGE This paper is a continuation of previous work on the preparation of nuclearly substituted styrenes from the corresponding ethylbenzenes by oxidation, hydrogenation and dehydration. l s 2 Ethylbenzene was chloromethylated by Blanc's procedure3 to give 7lYG of p-ethylbenzyl chloride. Blanc reported 6570. It was necessary to control the reaction temperature very closely a t 66-69' to avoid markedly lower yields. Treatment of p-ethylbenzyl chloride with sodium acetate in glacial acetic acid and with sodium ethylate in ethyl alcohol yielded p-ethylbenzyl acetate and p-ethylbenzyl ethyl ether, respectively. The yie1.d~ were over goyG. Oxidation of the latter compound with air in the presence of chromium oxide attacked the carbon atom carrying the alkoxy group t o give principally p-ethylbe.nzoic acid and ethyl p-ethylbenzoate. I n the prksence of chromium oxide and calcium carbonate p-ethylbenzyl acetate was oxidized to p-acetylbenzylacetate in Byo conversion and 3570 yield. This ketone was smoothly reduced to the corresponding carbinol with hydrogen in the presence of copper chromite. Some transesterification probab1:y took place during the hydrogenation, since the product boiled over a fairly wide range. J$,.ith aqueous potassium hydroxide this crude product yielded the glycol, p- (oc-hydroxyethyl)-benzyl alcohol, and with acetic anhydride i t yielded the diacetdte, p-( oc-acetoxyethy1)benzyl acetate. When p- (a-acetoxyethy1)-benzyl acetate was passed over a silica gel catalyst in the presence of steam a t 475-500°, a 72Y0 yield of p-vinylbenzyl acetate was obtained. Treatment of this compound with alcoholic potassium hydroxide yielded p-vinylbenzyl alcohol. Experimental p-Ethylbenzyl Chloride.-In a 1-liter, three-necked flask equipped with a stirrer, thermometer, gas inlet and reflux con'denser were placed 800 cc. of ethylbenzene, 60 g. of paraformaldehyde and 40 g. of fused and pulverized zinc chloride. Nrhi1e t his mixture wits stirred as vigorously as possible and thr iiiterual Leiriperature was held strictly at 66-69', t i vigorous streani of hydrogen chloride wab introduced uutil the mixture was baturated. At this point the flow was moderated, so that hydrogen chloride evolved slowly from the top of the condenser. The total reaction time was one hour. The hydrogen chloride flow y a s then After stopped and the reaction mixture cooled to 25 pouring into a 1-liter separatory funnel, the layers were separated and the ethylbenzene transferred to another 1 . (1) Emerson, Heyd, Lucas, Chapm, Owens and Shortridge, THIS JOURNAL, 68, 674 (1946). (2) Emerson, Heyd, Lucas. Cook, Owens ana Shortridge, ibid., 68, 1665 (1946). (3) Blanc, Bull soc chrm , 141 99, 313 (1923). liter separatory funnel t o free it from any zinc chloride adhering to the sides of the original funnel. The ethylbenzene solution was washed six times with water and then dried over sodium sulfate. Distillation yielded, besides recovered ethylbenzene, 222 g. (71% based on formaldehyde) of p-ethylbenzyl chloride, b. p. 94-100" (11 mm.), (106-110" (15 mm.)),* Ez5D 1.5293. p-Ethylbenzyl Ethyl Ether.-To a solution of 5 g. of sodium in 200 cc. of absolute ethyl alcohol was added 31 g. of p-ethylbenzyl chloride and the mixture was refluxed for four hours. Gpon cooling, it was diluted with water, acidified with acetic acid and the product extracted with benzene. Distillation of the benzene extracts yielded 31 g. (95%) of p-ethylbenzyl ethyl ether, b. p. 103-113" ~ (14 mm.), n Z 51.4921. An analytical sample boiled at 106-107" (14 mm.), EZ5D1.4918, d Z 5 2 s 0.923. AnnZ.5 Calcd. for CIIHIGO; 80.5; H, 9.76. Found: C, C, 80.7; H, 9.51. Oxidation of p-Ethylbenzyl Ethyl Ether.--8 stirred autoclave of about 1-liter capacity equipped with a stirrer, thermocouple well and reflux condenser with water trap was charged with 400 g. of p-ethylbenzyl ethyl ether and 4 g. of chromium oxide. IVhile the mixture was stirred a t 140", air a t 100 lb. per sq. in. mas blown through the bomb for six hours a t a rate of 2 cu. f t . per hr. Upon cooling, the bomb was opened and washed out with benzene. The combined reaction mixture and washings were filtered free of catalyst and then washed with sufficient aqueous sodium carbonate followed by water to remove all the acid products of the oxidation. When this extract was acidified, the precipitated p-ethylbenzoic acid was filtered, washed with water and dried. The yield was 80.1 g. (22%). I t was purified by treating its solution in ammonium hydroxide with hTorite and crystallizing the reprecipitated acid from 5070 alcohol and then &om water, in. p. 107.5-109.0" (113.5").ti After being dried over potassium carbonate, the benzene solution was fractionated through a short Vigreux column. Two fractions were collected: at 96-98' (12 nim.) (107 g., n * b ~1.5025) and a t 98-104" (12 mm.) (21 g., n P 5 ~ 1.4996) which represented a 32% recovery of crude p ethylhenzyl ethyl ether. There was then obtained 27 g. (6%) of ethyl p-ethylbenzoate, b. p. 113-115" (12 mm.); +D 1.5050, and 36 g. of high boiling oil, b. p. 116-156 ~ D (12 mm.), I Z ~ 1.5099. An analytical sample of the ethy! p-ethylbenzoate boiled a t 116" (13 mm.) (127.U-127.5 (16 trim.)),' n2% 1.5051 ( n Z 6 ~ 1.5065),1 dZ52;, 1.(171 (dP5,,!, 1.010) . I Anal. Calcd. for CI~H1402:C, 71.2; I-I, 7.87. I c o t i i i t l : C, 74.9; H, 8.12. Five grams of this material was refluxed for 3ile and onehalf hours with 40 cc. of 250; sodium hydroxide. The 2 cc. of distillate had n Z 51.3364 ( n P 5 D 1.3595 for ethyi ~ ztlcuhol) 7 and its 3,5-dinitrobenzoate melted ;it 88-92 (93' for ethyl 3,5-dinitrobenzoate) . 8 The acid in the residue was obtained by acidification with dilute phosphoric acid. After crystallization from alcohol and then from water, it was found to be p-ethylbenzoic acid, m . p. 109-110' (113.5 ") .6 (4) Jones, J . Chem. Soc., 1414 (1938). (5) All of the analyses are miroanalyses performed b y the Oakwold Laboratories, Alexandria, Virginia. (6) K i n d l a , .4nn., 452, 90 (1927). (7) Heilbion, "Dictionary of Organic Compounds," Oxford University Press, New York, N. Y . , 1934, Vol. 11. p. 16. (8) Shriner and Fuson, "Identification of Organic Compounds," John Wiley and Sons, New York, h. Y . , 1940, p. 185. 1906 EMERSON, HEYD,LUCAS, LYNESS, OWENSAND SHORTRIDGE Vol. 69 p-(a-Acetoxyethyl) -benzyl Acetate.-A mixture of 48 p-Ethylbenzyl Acetate.-A mixture of 110 g . of fused sodium acetate, 800 cc. of glacial acetic acid and 223 g. g. of crude p-(or-hydroxyethy1)-benzyl acetate, 24 g. of sodium acetate and 480 cc. of acetic anhydride was heated of p-ethylbenzyl chloride was refluxed for thirty minutes. Upon cooling, the precipitated sodium chloride was re- a t 100" for three hours and then allowed to stand overmoved by filtration, washed with 200 cc. of glacial acetic night. The acetic anhydride was then distilled until the acid, and these washings together with 25 g. of fused volume of the residue was reduced to 200 cc. before dilusodium acetate were added to the filtrate. This was then tion with 1.0 liter of water. After it had stood one hour, refluxed for an additional two and one-half hours before it was extracted three times with benzene. The combined dilution with water and removal of the product by benzene extracts were washed three times with water. Distillation f extraction. Distillation of this extract yielded 238 g. yielded 44 g. (75%) o p-(a-acetoxyethyl) -benzyl acetate, ~ 1.114. (93%) of p-ethylbenzyl acetate, b. p. 117-127" (14mm.), b. p. 144-153' (3 mm.), n Z 51.4998, daSz5 n 2 5 ~ 1.5018. An analytical sample of the compound Anal. Calcd. for C13Hl~01: C, 66.1; H, 6.78; sap. boiled a t 130-132" (15 mm.), nlSD 1.5042, dlsas 1.028. equiv., 118. Found: C, 66.0; H , 6.73; sap. equiv., Anal. Calcd. for C1lH1402;C, 74.3; H, 7.86. Found: 125, 123. C, 73.9; H , 7.91. p-Viylbenzyl Acetate.-A quartz tube similar to that p-Acetylbenzyl Acetate .-A vigorous stream of air was described previouslyg was packed with a silica gel catalyst. introduced through an alundum disperser into a mixture While the tube was kept a t 475-500 and steam was introof 485 g. of p-ethylbenzyl acetate, 5 g. of chromium oxide duced a t a pressure of 25-30 mm., 139.5 g. of p-(a-acetoxyand 20 g. of calcium carbonate held a t 130-140" for ethyl) -benzyl acetate was introduced over a one hundredtwenty-eight hours. Upon cooling, the catalyst was re- minute period. The tube was steamed for another ten moved by filtration, and the filtered product was then re- minutes, cooled and washed with benzene. The comfluxed for two hours with 10 g. of sodium acetate and 100 bined distillate and washings were twice extracted with cc. of acetic anhydride. After dilution with water, the benzene. The combined extracts were distilled from product was extracted with benzene and distilled to give sulfur and hydroquinone to give 57 g. (55%) of p-vinyl287 g. (59% recovery) of p-ethylbenzyl acetate, b. p. benzyl acetate, b. p. 128-158" (15 mm.), n% 1.5348, ~ 119-129" (12 mm.), n 2 5 1.5011, and 118 g. (23% con- and 33 g. of p-acetylbenzyl acetate, b. p. 158-178" (15 ~ version and 55% yield) of p-acetylbenzyl acetate, b. p. mm.), n a 61.5201. The latter compound was apparently ~ 165-185" (12 mm.), n a 5 1.5225. An analytical sample present in the crude p-(a-acetoxyethyl) -benzyl acetate which was obtained from a different reduction than that 0 1.126. boiled a t 161-163" (11rnm.), nZ5D1.5225, % Anal. Calcd. for CllH1203: C, 68.8; H , 6.25. Found: described above. Correction therefor raises the yield of p-vinylbenzyl acetate to 72%. An analytical sample C, 68.9; H, 6.66. melted at 182-183 'after boiled a t 136-139" (15 mm.), nZ5D1.5350, dZ525 1.051. Its 2,4-dinitrophenylhydrazone Anal. Calcd. for CllHllOz: C, 75.0; H , 6.82. Found: one crystallization from ethyl acetate. C, 75.1; H, 6.96. Anal. Calcd. for C17H1606Nd: PUT, 15.1. Found: N, p-Vinylbenzyl Alcohol.-A solution of 3.5 g. of p-vinyl15.0. benzyl acetate, 3.5 g. of potassium hydroxide, 0 . 5 g. of Its semicarbazone was crystallized twice from 60% sulfur and 0.5 g. of hydroquinone in 25 cc. of ethyl alcohol alcohol and twice from 95% alcohol, m. p. 166-167 was boiled under reflux for one-half hour. It was then Anal. Calcd. for C I Z H ~ ~ O C,N57.8; H, 6.02; N, diluted with 200 cc. of water, acidified with 5 cc. of glacial ~ ~: 16.9. Found: C,58.0; H,6.05; N, 16.9. acetic acid and twice extracted with benzene. The comp-(a-Hydroxyethyl)-benzyl Acetate.-A mixture of 215 bined extracts were filtered and distilled to yield 1 g. g. of P-acetylbenzyl acetate and 25 g. of copper chromite (38%) of p-vinylbenzyl alcohol, b. p. 132-137" (15 m m . ) , was shaken for six hours in standard equipment with hy- ZISD 1.5697. The sample was redistilled a t 5 mm. before drogen a t an initial pre%sureof 2000 pounds. Reduction analysis. was effected a t 135-155 . Upon cooling, the charge was Anal. Calcd. for CgHloO: C, 80.6; H , 7.47. Found: removed from the bomb, filtered and the precipitate washed C, 79.8; H, 7.37. with benzene. Distillation of the filtrate yielded 184 g. (8570) of crude p-(a-hydroxyethy1)-benzyl acetate, b. p. Summary 135-160" (3 mm.). The liquid phase oxidation of p-ethylbenzyl acep-(a-Hydroxyethyl) -benzyl Alcohol.-A mixture of 48 g. of crude p-(a-hydroxyethyl) -benzyl acetate, 56 g. of tate to p-acetylbenzyl acetate has been effected in potassium hydroxide and 500 cc. of water was boiled 23% conversion and 55y0 yield. This reaction, under reflux overnight. After cooling, the solution was saturated with potassium carbonate and the organic layer followed by hydrogenation, acetylation and pyseparated. I t was distilled to give 10 g. (27%) of p - ( a - rolysis, constitutes a convenient synthesis of phydrosyethy1)-benzyl alcohol, b. p. 170" (7 nim.), n z 5 ~ vinylbenzyl acetate. 1.5493, a 2 5 2 5 1.122. OHIO RECEIVED MARCH 1947 24, Anal. Calcd. for CgH1202: C, 71.1; H, 7.90. Found: DAYTON, C, 7 .O; H, 1 7.92. ( 9 ) Emerson and Agnew, THISJ O U R N A L , 67, 618 (194.5) .