Question

Why is excess ammonia used in the preceding reaction?

Short answer

Reductive amination involves the formation of amine from carbonyl compounds particularly aldehyde or ketone via from the imine intermediate.

Step-by-step solution

Reductive amination

Reductive amination involves the formation of amine from carbonyl compounds particularly aldehyde or ketone via from the imine intermediate.

Explaination

In this reaction excess ammonia is used because one equivalent of ammonia first reacts with acidic proton and forms NH⁺₄ion and loses its nucleophilicity. Then the remaining ammonia substitutes the Br^-. So, excess of ammonia is used in this reaction.

The reaction is represented as follows: