a. Explain why the reaction of an alkyl halide with ammonia gives a low yield of primary

Question:

a. Explain why the reaction of an alkyl halide with ammonia gives a low yield of primary amine.
b. Explain why a much better yield of primary amine is obtained from the reaction of an alkyl halide with azide ion followed by catalytic hydrogenation. (An alkyl azide is not nucleophilic.)