How to prepare p-bromoaniline, knowing that aniline only gives the tris-brominated product; note that bromination of aniline does not stop at the monobrominated stage and cannot be moderated by using only one equivalent of bromine.

SOLUTION:

Moderating the activity of NH₂ by reacting of aniline with acetic anhydride

The activating influence of NH₂ has been reduced due to competing withdrawal of N-lone pair by carbonyl group:

Related Questions:

1. Why do not Friedel-Crafts reactions succeed on aromatic rings that are substituted either by a strongly electron-withdrawing group such as carbonyl (C=O) or by an amino group (-NH₂, NHR, -NR₂):
2. Why does not aniline undergo Friedel crafts reactions explain?
3. Why Friedel–Crafts alkylations often give polysubstitution products but Friedel–Crafts acylations do not.