Question

Which of the following is converted into an alcohol on treatment with \[HN{{O}_{2}}.\]
A.Methyl amine.
B.Aniline.
C.Dimethyl amine.
D.Triethylamine.

Answer 1

Hint: We know that aniline reacts similarly to primary aliphatic amines. Aniline gives diazonium ions after treatment with nitrous acid. On further treatment with dilute acid undergo hydrolysis reaction. Amines are known as derivatives of ammonia in which one or more of the hydrogen atoms of ammonia have been replaced by alkyl groups.

Complete answer: In organic chemistry amines are those compounds and functional groups that contain a basic nitrogen atom with lone pair. These are derivatives of ammonia in which one or more hydrogen atoms of ammonia are replaced by any alkyl or aryl group.
Amines can also be known by the name alkylamines and arylamines as one or more hydrogen groups of ammonia is replaced with alkyl or aryl groups. Amines can be further classified according to the nature and number of substituents on nitrogen. Aliphatic amines contain only Hydrogen and alkyl substituents while Aromatic amines have the nitrogen atom connected to an aromatic ring.
There are three types of amines; primary, secondary and tertiary depending upon the number of alkyl groups attached to the nitrogen atom of ammonia. Each type of amine gives a different product on reaction with nitrous acid. Primary, secondary and tertiary amines show different reactions with nitrous acid. Only primary amines liberate nitrogen gas on reaction with nitrous acid. So we can use nitrous acid reagent to distinguish primary, secondary and tertiary amines. Only methyl amine is converted into alcohol when treated with \[HN{{O}_{2}}.\]
\[\underset{Methylamine\text{ }}{\mathop{C{{H}_{3}}N{{H}_{2}}}}\,~\xrightarrow{HN{{O}_{2}}\text{ }}C{{H}_{3}}OH+{{N}_{2}}+{{H}_{2}}O.\]
Therefore, the correct answer is option A.

Note:
Remember that the 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.