248 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Alkyl Anilines. 



Aniline as a primary amine will react with one or two molecules of an 

 alkyl halide to form alkyl anilines : 



C 6 H 6 . NH 2 + CH 3 I = C 6 H. . NH . CH- + HI 

 C 6 H 5 . NH . CH 3 + CH 3 I = C 6 H 5 . N . (CH 3 ) a + HI. 



These compounds are readily obtained by heating aniline with the alcohol 

 and hydrochloric acid at 200 to 250: 



C B H 5 NH 2 . HC1 + CH 3 OH = C 6 H B NH . CH 3 HC1 + H 2 O 

 C 6 H 5 NH 2 . HC1 + 2CH 3 OH = C 6 H 5 . N(CH 3 ) 2 HC1 + 2 H 2 O. 



The methyl anilines are stronger bases than aniline, as they are more like 

 the aliphatic amines. They may be regarded as phenylmethylamine and 

 phenyldimethylamine. 



Methyl aniline is a colourless oily liquid which boils at 192. As a 

 secondary amine it gives a nitrosamine with nitrous acid. 



C TT C T-f \ 



iN \NH + O:N.OH = )N . NO + H 2 O. 



CH 3 / CH 3 / 



Phenyl-methyl-nitrosamine is a yellow oil which gives Liebermann's 

 nitroso reaction. 



Dimethylaniline is a colourless oil which boils at 192; it is largely used 

 in the dye industry. 



Dialkylanilines, such as dimethylaniline, react with nitrous acid giving 

 nitroso compounds : in these compounds the reaction takes place with the 

 hydrogen atom in the para position (p. 260) in the benzene nucleus: 



/NO 

 C 6 H fl . N(CH 3 ) 2 + ONOH = C 6 H 4 / 



\N(CH 3 ) a + H 2 0. 



Diphenylamine cannot be prepared by heating aniline with bromoben- 

 zene, but is obtained by heating aniline hydrochloride with aniline in a closed 

 vessel at 240. 



C 6 H 6 NH a . HC1 + C 6 H 5 NH 2 = >NH + NH 4 C1. 



/ 



Diphenylamine is a crystalline solid melting at 54 and boiling at 310. 

 It is a very weak base, its salts being decomposed by water; it is almost 

 insoluble in dilute acids. It dissolves in concentrated sulphuric acid. This 

 solution on the addition of a trace of nitric acid gives a deep blue coloration 

 and serves for detecting nitrates. Diphenylamine owing to the acid char- 

 acter of the phenyl groups reacts with potassium giving potassium diphenyl- 

 amine, 



C tt H 5X 



)NK. 

 CH B / 



Triphenylamine. (C C II 5 ) 3 N. 



This compound is prepared by heating potassium diphenylamine with 

 bromobenzene at 300. It is a colourless crystalline solid melting at 127. It 

 does not form salts with acids. 



