Question

Give reasons for the following:

Ammonolysis of alkyl halides is not a good method to prepare pure primary amines.

Answer 1

Ammonolysis of alkyl halides leads to the formation of a mixture of primary, secondary, tertiary amines and quaternary salts. It is because every time a nucleophilic substitution reaction takes place, an amine acts as a nucleophile and forms a primary amine, which further reacts and forms a secondary amine, which again reacts with the alkyl halide to form a tertiary amine and further leads to the formation of a quaternary salt. Thus, the ammonolysis reaction forms a mixture of all four compounds, and it will be difficult to get the pure amine.

\[\ce{\underset{Alkyl halide}{R-X}  ->[NH3][-HX] R - NH2 ->[R-X][-HX] R2NH ->[R-X][-HX] R3N ->[R-X] R4\overset{+}{N}X^-}\]