Question

Answer the following

Write a reaction to convert Aniline into p-bromoaniline.

Answer 1

–NH₂ group in aniline is highly ringing activating and o-/p- directing due to the involvement of the lone pair of electrons on ‘N’ in resonance with the ring. As a result, on reaction with Br₂, it gives 2,4,6-tribromoniline. To get a monobromo product, it is necessary to decrease the ring activating effect of -NH₂ group. This is done by acetylation of aniline. The lone pair of ‘N’ in acetanilide is also involved in resonance in the acetyl group. To that extent ring activation decreases.

Hence, acetanilide on bromination gives a monobromo product p-bromoacetanilide. After monobromination, the original -NH₂ group is regenerated. The protection of the -NH₂ group in the form of acetyl group is removed by acid-catalyzed hydrolysis to get p-bromoaniline, as shown in the following scheme.