( viii) Electrophihc substitution reactions Aniline is ortho and para directing towards electrophilic substitution reaction due to high electron density at ortho and para-positions.
To prepare monosubstituted derivative, activating effect of-NH2 group must be controlled. It can be done by protecting the-NH2 group by acetylation with acetic anhydride.
( b) Nitration Direct nitration of aniline is not possible as it is susceptible to oxidation, thus amino group is first protected by acetylation.