VII
ETHYL PHENYLACETATE
C6H5CH2CN + C2H5OH + H2SO4 + H2O—> C6H5CH2CO2C2H5 + NH4HSO4
Prepared by ROGER ADAMS and A. F. THAL. Checked by OLIVER KAMM.
1. Procedure
IN a 3-l. round-bottom flask, fitted with an efficient reflux condenser, are mixed 750 g. of 95 per cent alcohol, 750 g. of concentrated sulfuric acid and 450 g. of benzyl cyanide. The mixture, which soon separates into two layers, is heated to boiling over a low flame, for six to seven hours, cooled and poured into 2 l. of water, and the upper layer is separated. This is washed with a little 10 per cent sodium carbonate solution to remove small amounts of phenylacetic acid which may have been formed, and then distilled in vacuo. A small amount of water goes over first and then a pure product boiling 132-138'0/32 mm. (120-125'0/17-18 mm.). The yield varies in general between 525 and 550 g. (83-87 per cent of the theoretical amount).
2. Notes
The benzyl cyanide can be most conveniently prepared according to the directions in preparation III (p. 9); the product which boils over a 5'0 range should be used.
In washing the layer of ethyl phenylacetate with sodium carbonate it is sometimes advisable to add a certain amount of sodium chloride so that the ester will separate more readily.
The product obtained is water-clear and practically colorless. Although the product is collected over a 5'0 range, most of the liquid is found to boil over a 1'0 range, if distilled slowly without superheating.
The boiling point of ethyl phenylacetate is near that of benzyl cyanide. However, a Kjeldahl analysis of the product shows that only a trace of nitrogen compounds is present.
3. Other Methods of Preparation
Ethyl phenylacetate may be prepared by the treatment of benzyl cyanide with alcohol and hydrochloric acid gas.[1] It is much more convenient in the laboratory, however, to use sulfuric acid in place of hydrochloric acid; in fact, the yields obtained are better than those recorded in the literature. This ester may also be made by the esterification of phenylacetic acid with hydrochloric acid and alcohol;[2] or with alcohol and sulfuric acid;[3] the following less important methods of preparation may be mentioned; the action of benzyl magnesium chloride upon ethyl chlorocarbonate,[4] and the action of copper on a mixture of bromobenzene and ethyl chloroacetate at 180'0.[5]
[1] Ber. 20, 592 (1887); Ann. 296, 361 (1897)
[2] Ber. 2, 208 (1869).
[3] Ann. 296, 2, footnote (1897); Compt. rend. 152, 1855 (1911).
[4] Ber. 36, 3088 (1903).
[5] Ber. 2, 738 (1869).