Question

In the diazotization of aryl amines with sodium nitrite and hydrochloric acid, an excess of hydrochloric acid is used primarily to :

• A. supress the concentration of free aniline available for coupling
• B. supress hydrolysis of phenol
• C. ensure a stoichiometric amount of nitrous acid
• D. neutralise the base liberated

Answer 1

The correct option is A supress the concentration of free aniline available for coupling

If excess $HCl$ is not used, the arene diazonium salt will react with free aniline to form azo compound.

Excess $HCl$ forms hydrochloride salt of aniline. This prevents azo coupling.

Option A is correct.