34.2.2—Describe

The –NH₂ group activates the aromatic ring: phenylamine reacts with bromine water at room temperature to give rapid substitution. With nitrous acid made from NaNO₂ and dilute acid below 10 °C, it forms a diazonium salt; warming with water gives phenol.

Keep the conditions separate: bromination is an aromatic substitution, while diazotisation requires cold acid and the next hydrolysis step requires warming.

Phenylamine + Br₂(aq) gives 2,4,6-tribromophenylamine; the diazonium salt route then releases N₂ as phenol forms.

Do not warm during diazotisation or use bromine conditions to infer the diazonium route.