Question

A compound X on reaction with chloroform and NaOH gives a compound with a very unpleasant odour. X is
A. \[{C_6}{H_5}CON{H_2}\]
B. \[{C_6}{H_5}N{H_2}\]
C. \[{C_6}{H_5}C{H_2}NHC{H_3}\]
D. \[{C_6}{H_5}NHC{H_3}\]

Answer 1

Hint: Primary amine is heated with chloroform and alcoholic potassium hydroxide to form isocyanides or carbylamines. This reaction is known as the carbylamines reaction.

Complete Step by Step Solution:
It is given that, a compound X on reaction with chloroform and NaOH gives a compound with a very unpleasant odour.
On heating aliphatic or aromatic primary amine with chloroform and alcoholic potassium hydroxide, isocyanide or carbylamines compound is formed as the main product. This reaction is referred to as the carbylamines reaction.
The carbylamines reaction is used to detect the presence of primary amines. If the primary amine is present, it will form isocyanide on heating with chloroform and alc. potassium hydroxide. The formation of isocyanide is recognised by a very foul odour.
When secondary and tertiary amine is heated with chloroform and alcoholic potassium hydroxide, it does not give any foul odour which determines that secondary and tertiary amine does not give a carbylamines reaction.
A primary amine is a compound where one carbon atom is bonded to the nitrogen atom. In secondary amine, two carbon atom is bonded to the nitrogen atom whereas, in tertiary amine, the three-carbon atom is bonded to a nitrogen atom.
From the given option, B is the primary amine.
The reaction is shown below.
\[{C_6}{H_5}N{H_2} + CHC{l_3} + 3NaOH \to 3NaCl + 3{H_2}O + {C_6}{H_5} - N \equiv C\]
In the above reaction, one mole of aniline reacts with one mole of chloroform and three moles of sodium hydroxide to form three moles of sodium chloride, three moles of water and one mole of phenyl isocyanide.
Therefore, the correct option is B.

Note: It should be noted that only primary amine is converted to isocyanides or carbylamines whereas secondary amine and tertiary amine do not give carbylamine reactions. This reaction is also known as Hoffmann’s isocyanide test.