From diazonium salts
A diazonium salt is formed by treating an aromatic primary amine
with nitrous acid (NaNO2 + HCl) at 273-278 K Diazonium salts are
hydrolysed to phenols by warming with  water or by treating with
dilute acids (Unit 9, Class XII) H O
OH
NH2
NaNO2
+HCl
Aniline
N Cl
2
2
N   + HCl
2
+
Benzene diazonium
chloride
Warm
+
–
4 From cumene
Phenol is manufactured from the hydrocarbon, cumene