When an alkyl or benzyl hallide allowed to react with an ethanolic solution of ammonia, it undergoes nucleophilic substitution reaction in which the halogen atom is replaced by amino (-NH2 group) The process of cleavage of the C-X bond by ammonia is called Ammonolysis.
When this substituted ammonium salt is treated with a strong base such as sodium hydroxide, amine is formed.
Though primary amine is produced as the major product, this process produces a mixture of primary, secondary and tertiary amines and also quaternary ammonium salts as shown below:
This method cannot be used for the preparation of arylamines (aniline) since aryl halides are much less reactive than alkyl halides towards nucleophilic substitution reaction.
Note: Nucleophilic substitution reaction is the reaction of an electron pair donor (Nu, the nucleophile) with the electron pair acceptor (the electrophile) For example:
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(a) Write the reactions involved in the following :
(i) Hofmann bromamide degradation reaction
(iii) Gabriel phthalamide synthesis
(b) Give reasons :
(i) (CH3)2NH is more basic than (CH3)3N in an aqueous solution.
(ii) Aromatic diazonium salts are more stable than aliphatic diazonium salts.
(a) Write the structures of the main products of the following reactions:
(b) Give a simple chemical test to distinguish between Aniline and N,N-dimethylaniline.
(c) Arrange the following in the increasing order of their pKb value:
C6H5NH2, C2H5NH2, C6H5NHCH3Chemistry - Board Papers