Question

Reaction of aniline with ${\text{HN}}{{\text{O}}_{\text{2}}}$ followed by treatment of dilute acid gives:
A) ${{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}{\text{NHOH}}$
B) ${{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}{\text{OH}}$
C) ${{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}{\text{NHN}}{{\text{H}}_{\text{2}}}$
D) ${{\text{C}}_{\text{6}}}{{\text{H}}_6}$

Answer 1

Aniline reacts similarly to primary aliphatic amines. Aniline gives diazonium ion after treatment with nitrous acid. On further treatment with dilute acid undergo hydrolysis reaction.

Complete solution:
In this reaction, aniline is the reactant and reagent given to us is nitrous acid, ${\text{HN}}{{\text{O}}_{\text{2}}}$ and dilute acid.
Aniline is the simplest aromatic amine that behaves similarly to primary aliphatic amines. It consists of an amino group bonded to a phenyl group.
Reagent nitrous acid is prepared by reaction of sodium nitrite with hydrochloric acid. It is a weak acid
${\text{NaN}}{{\text{O}}_{\text{2}}}{\text{ + HCl}} \to {\text{ NaCl + HN}}{{\text{O}}_{\text{2}}}$
Now, we will see the reaction mechanism when of aniline reacts with ${\text{HN}}{{\text{O}}_{\text{2}}}$ followed by treatment with dilute acid.
Step 1: Conversion of aniline to diazonium ion using nitrous acid, ${\text{HN}}{{\text{O}}_{\text{2}}}$reagent.

Step 2: Diazonium ion on further treatment with dilute acid undergoes hydrolysis reaction and gives phenol as the product.

Thus, the correct options are (B).

Note: Aromatic diazonium ion is a very important intermediate to produce substituted benzene. The final product depends on reagent use. Here the reagent used is dilute acid so the diazonium ion undergoes a hydrolysis reaction. The addition of water molecules is known as the hydrolysis reaction. Amines on hydrolysis give alcohol as the product while aniline gives phenol as the product.