Question

Isocyanide test can be given by (This question has multiple correct answers)
(A) ${{C}_{2}}{{H}_{5}}N{{H}_{2}}$
(B) ${{C}_{6}}{{H}_{5}}N{{H}_{2}}$
(C) ${{C}_{6}}{{H}_{5}}NH{{C}_{2}}{{H}_{5}}$
(D) ${{C}_{6}}{{H}_{5}}-CH({{C}_{2}}{{H}_{5}})-N{{H}_{2}}$

Answer 1

Hint: This reaction is called the carbylamine reaction and thus reaction takes place with electrophiles. The main product of this reaction is Isocyanide. Only that compound in which the nitrogen has 2 hydrogen atoms attached to it gives isocyanide.

Complete step by step solution:
The nitrogen atom has lone pairs present and due to the presence of a lone pair of electron on the nitrogen atom, animes like ammonia are good nucleophiles and hence react with a variety of electrophiles (electron-deficient compounds) such as metal ions, alkyl halides, acid chlorides, acid anhydrides, chloroform, etc.
Reaction with chloroform- This reaction is called carbylamine reaction. It is also known as an isocyanide test.
Both aliphatic and aromatic primary amines give this reaction when they are warmed with chloroform and an alcoholic solution of KOH, they produce isocyanide or carbylamines which have a very unpleasant odour.
Primary amines are those in which the nitrogen has 2 hydrogen atoms.
(a)- ${{C}_{2}}{{H}_{5}}N{{H}_{2}}$
This is a primary amine compound, so it will give the isocyanide test. The reaction is:
${{C}_{2}}{{H}_{5}}-N{{H}_{2}}+CHC{{l}_{3}}+3KOH\to {{C}_{2}}{{H}_{5}}-N\equiv C+3KCl+3{{H}_{2}}O$
(b)- ${{C}_{6}}{{H}_{5}}N{{H}_{2}}$
This is a primary amine compound, so it will give the isocyanide test. The reaction is:
${{C}_{6}}{{H}_{5}}-N{{H}_{2}}+CHC{{l}_{3}}+3KOH\to {{C}_{6}}{{H}_{5}}-N\equiv C+3KCl+3{{H}_{2}}O$
(c)- ${{C}_{6}}{{H}_{5}}NH{{C}_{2}}{{H}_{5}}$
This is a secondary amine so it will not give an isocyanide test.
(d)- ${{C}_{6}}{{H}_{5}}-CH({{C}_{2}}{{H}_{5}})-N{{H}_{2}}$
This is a primary amine compound, so it will give the isocyanide test. The reaction is:
${{C}_{6}}{{H}_{5}}-CH({{C}_{2}}{{H}_{5}})-N{{H}_{2}}+CHC{{l}_{3}}+3KOH\to {{C}_{6}}{{H}_{5}}-CH({{C}_{2}}{{H}_{5}})-N\equiv C+3KCl+3{{H}_{2}}O$

So, the correct answers are (A), (B), and (D).

Note: This reaction is not given by secondary and tertiary amines (both aliphatic and aromatic compounds). Therefore, it is used to distinguish primary amines from secondary and tertiary amines.