Why is it difficult topreparepure amines by Hofmann’s ammonolysis?

Explanation

Ammonolysis of alkyl halides involves the action of a ammonia on alkyl halides. Ammonia with its lone pair of electrons act as a nucleophile and attack the alkyl halide to give a primary amine. As this primary amine also contains a lone pair of electron it further attacks another molecule of alkyl halides to give a secondary amine. This process goes on till the formation of a quaternary ammonium salt take place. The process stops here as the nitrogen atom in this salt as it does not have a lone pair of electrons.

The separation of this mixture of amine is very difficult. Therefore it is difficult to prepare pure amines by ammonolysis of alkyl halides.