Question

In the preparation of chlorobenzene from aniline, the most suitable reagent is

• A. Nitrous acid followed by heating with $C{u}_{2}C{l}_2$
• B. Chlorine in the presence of $AlC{l}_3$
• C. Chlorine in the presence of ultraviolet light
• D. None of these

Answer 1

The correct option is A Nitrous acid followed by heating with $C{u}_{2}C{l}_2$

Amines on reacting with nitrous acid in acidic condition at $0^{\circ }$ will form diazonium salts.
When these diazonium salts are heating with $C{u}_{2}C{l}_2$ it gives alkyl chlorides. This preparation method of alkyl halide from diazonium salts is called as Sandmeyer's reaction.
Aniline on reacting with nitrous acid in acidic condition at $0^{\circ }$ will give benzene diazonium salt.
When this salt is heated with $C{u}_{2}C{l}_2$ give chlorobenzene.


Aniline in presence of $AlC{l}_3$ will undergo acid-base reaction and chlorination by free radical mechanism does not occur in benzene molecule.
Hence, (a) is correct.