The activating effect of –NH₂ group can be controlled by protecting the -NH₂ group by acetylation with acetic anhydride, and then carrying out the desired substitution followed by hydrolysis of the substituted amide to the substituted amine.

The acetylation of —NH₂ group of aniline reduce its activating effect because the lone pair of electrons on nitrogen of acetanilide interacts with oxygen atom due to resonance.