258 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Acetophenone, C 6 H 5 . CO . CH 3 . 



Acetophenone is an example of an aromatic ketone. It is formed by 

 distilling calcium benzoate with calcium acetate. 



Acetophenone is most readily prepared by slowly dropping i molecular 

 proporticn of acetyl chloride upon i molecule of benzene containing in 

 suspension i molecule of aluminium chloride and cooled with ice. When the 

 evolution of hydrochloric acid is over, ice-cold water is very carefully added. 

 The solution is extracted with ether, the ethereal extract dried and distilled. 

 Acetophenone passes over between 194 and 200 : 



C 6 H 6 + CH 3 COC1 = C 6 H 6 . CO . CH 3 + HC1. 



This reaction is a general one for preparing aromatic ketones. 



Acetophenone is a crystalline solid melting at 20*5 and boiling at 202. 

 It is soluble in water and alcohol. It is sometimes used as a hypnotic under 

 the term hypnone. It closely resembles acetone and the aliphatic ketones in 

 giving a secondary alcohol on reduction, benzoic acid and acetic acid on 

 oxidation and in forming an oxime and a phenylhydrazone. It resembles 

 benzene in forming nitro- and other derivatives. 



Benzophenone, C 6 H 5 . CO . 



Benzophenone is obtained by heating calcium benzoate and is prepared 

 by the action of benzoyl chloride upon benzene in the presence of aluminium 

 chloride. 



It is a crystalline solid melting at 48-49 and resembles acetophenone. 

 .It yields diphenylmethane on reduction with zinc dust. 



Phenylacetic Acid, CH 6 . CH 2 . COOH. 



This acid containing a carboxyl group in the side chain is formed 

 in the putrefaction of proteins, arising from phenylalanine. 

 Synthetically it is obtained from benzyl chloride : 



C 6 H 5 . CH 2 C1 - C 6 H 8 . CH 2 . CN -> C 6 H 6 . CH a . COOH. 



Molecular proportions of benzyl chloride and potassium cyanide are 

 boiled in dilute alcoholic solution for 3-4 hours. The benzyl cyanide is isolated 

 by fractional distillation (220-335 fraction) and hydrolysed by boiling with 

 dilute sulphuric acid. The phenylacetic acid is purified by crystallisation. 



Phenylacetic acid crystallises in colourless shining plates which melt at 

 76*5 and boil at 262. It has a characteristic smell. 



Phenaceturic Acid, CH 5 . CH 2 . CO NH . CH 2 . COOH. 



Phenylacetic acid, which is formed in the large intestine in small amounts, 

 on absorption into the body, or when it is injected into the blood, is excreted 

 as phenaceturic acid, i.e. in combination with glycine. It thus resembles 

 benzoic acid, which is excreted as hippuric acid (p. 142). 



It is a colourless crystalline substance melting at 143, is soluble with 

 difficulty in water, but easily in alcohol. It is hydrolysed by boiling with 

 acids into phenylacetic acid and glycine. 



Phenylpropionic Acid, QH 5 . CH 2 . CH 2 . COOH. 



Phenylpropionic acid accompanies phenylacetic acid amongst the putre- 

 faction products of proteins. 



It is most conveniently prepared by reducing cinnamic acid : 



CH S . CH = CH . COOH + H. = C 6 H 8 . CH 2 . CH, . COOH. 

 It is a colourless crystalline substance melting at 47 and boiling at 280. 



