AMINES. 



The amines are compounds which are derived from ammonia by 

 the replacement of one, two, or three of its hydrogen atoms by alkyl 



groups, e.g. 



CH 3 NH 2 (C 2 H 5 ) 2 :NH (CH 3 ) 3 : N 



(Mono)methylamine. Diethylamine. Trimethylamine. 



Their relationship to the hydrocarbons is shown by their method 

 of preparation from the alkyl halides. Primary amines may be re- 

 garded as derived from hydrocarbons in which a hydrogen atom has 

 been replaced by the amino (NH 2 ) group, or as derived from alcohols 

 in which the hydroxyl group has been replaced by the amino group. 

 Numerous amines occur in nature ; they are products of decomposi- 

 tion of the amino acids, which lose carbon dioxide during putrefac- 

 tion. 



Preparation. 



When an alkyl halide is treated with alcoholic ammonia, the 

 halogen atom is replaced by the NH 2 group. This new compound 

 again reacts with the alkyl halide, and the reaction continues until all 

 the hydrogen atoms of ammonia are substituted by alkyl groups : 



CH 3 C1 + NH 3 = HC1 + CH 3 . NH 2 

 CH 3 C1 + CH 3 . NH 2 = HC1 + CH 3 . NH . CH 3 

 CH 3 C1 + (CH 3 ) 2 : NH = HC1 + (CH,) 2 : N.CH 3 . 



A mixture of the three compounds is obtained. 



The three compounds are termed respectively a primary, a 

 secondary, and a tertiary amine according as I, 2, and 3 of the 

 hydrogen atoms in ammonia are replaced by alkyl groups. If the 

 alkyl groups are the same, they are known as simple amines, if 

 different, as in methylethylamine, they are known as mixed amines. 



Primary amines are characterised by the presence of the amino 

 (*NH 2 ) group; secondary amines are characterised by the presence of 

 the imino (:NH) group ; tertiary amines by N completely substituted 

 by alkyl groups. 



Primary amines can also be prepared : 



(1) By the hydrolysis of isocyanates : 



CH 3 .CH 2 .N.CO + 2 NaOH = CH 3 .CH 2 .NH 2 + Na 2 CO 3 , 

 Primary amines were first prepared by this reaction by Wurtz in 

 1849; 



(2) By the reduction of nitriles (p. 158): 



CH 3 . CN + 2H 2 = CH 8 . CH 2 . NH 2 . 



This reaction serves for passing from a lower to a higher series. 



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