AROMATIC COMPOUNDS 257 



Benzamide, C 6 H 5 . CO . NH 2 . 



Benzamide is prepared by either of the reactions : 



(1) Benzoyl chloride and ammonia : 



CfiHgCOCl + NH 3 = C 6 H 6 . CO. NH a + HC1. 



Benzoyl chloride is mixed with a slight excess of dry ammonium carbonate 

 in a mortar until the smell of benzoyl chloride vanishes. Cold water is added 

 to dissolve the ammonium salts ; the insoluble benzamide is crystallised from 

 hot water. 



(2) Ammonia and ethyl benzoate. 



Benzamide is a colourless crystalline solid melting at 130, easily soluble 

 in hot water, but soluble with difficulty in cold. It is decomposed by boiling 

 with acids, or alkalies, into benzoic acid and ammonia. 



Benzonitrile, or Phenyl Cyanide, C g H 5 . CN. 



Benzonitrile is prepared : 



(1) by fusing potassium benzene sulphonate with potassium cyanide or 

 ferrocyanide : 



C 6 H 5 S0 3 K + KCN = C 6 H 8 CN + K 2 SO 3 . 



(2) by Sandmeyer's reaction from aniline; the aniline is diazotised and 

 the solution heated with cuprous cyanide (p. 250). 



Benzonitrile is a colourless oil with a smell resembling that of nitroben- 

 zene. It boils at 191 and resembles the aliphatic nitriles in its reactions : 



(1) hydrolysis : 



C 6 H 5 CN + 2H 2 O = C a H 6 COOH + NH 3 , 



(2) reduction : 



C 6 H 5 CN + 4 H = C 6 H 6 . CH 2 . NH a 

 Benzylamine. 



Benzylamine, C 6 H 5 . CH 2 . NH 2 . 



Benzylamine is an aromatic amine in which the amino group is present 

 in the side chain (compare aniline). It is prepared like the aliphatic 

 primary amines (p. 124) : 



(1) ammonia upon benzyl chloride ; 



(2) bromine and potash upon the amide of phenylacetic acid ; 



(3) reduction of the nitrile or oxime. 



It is a colourless oily liquid boiling at 187 with pungent smell. It is 

 a strong base like the aliphatic primary amines and with similar properties. 



Dibenzylamine, (C 6 H 5 .CH 2 ) 2 NH. Tribenzylamine, (CH 5 .CH 2 \N. 



Again, these compounds resemble the secondary and tertiary aliphatic 

 amines. They are obtained by heating benzylamine with benzylchloride. 



The three amines are formed when benzylchloride is heated with 

 ammonia. 



They have the typical aromatic reactions, as well as the aliphatic ones. 



