Question

An organic compound 'A' having molecular formula ${{C}_{2}}{{H}_{3}}N$ on reduction gave another compound 'B', upon treatment with nitrous acid 'B' gave ethyl alcohol. On warming with chloroform and alcoholic KOH, it formed an offensive smelling 'C'. The compound 'C' is:
(A) $C{{H}_{3}}C{{H}_{2}}N{{H}_{2}}$
(B) $C{{H}_{3}}C{{H}_{2}}N\equiv C$
(C) $C{{H}_{3}}N\equiv C$
(D) $C{{H}_{3}}C{{H}_{2}}OH$

Answer 1

Identify the reagents used in the reaction and the reaction mechanism for the same as well. Reduction helps to convert the compound into amine. Later nitrous acid replaces the amine group with alcohol thus giving alcohol as a product. chloroform and alcoholic KOH indicate the carbylamine test.

Complete step by step answer:
We will start the reaction with the compound 'A' and a possible structure of the same. If the final product matches with the product given in question, we will conclude that our assumption was right and the reaction mechanism as well.
The possible structure of 'A' is taken as :
$C{{H}_{3}}N\equiv C$

Upon reduction, the compound will give a primary amine as a product. The name of the compound is ethyl amine and the possible structure of compound 'B'.
$C{{H}_{3}}C{{H}_{2}}N{{H}_{2}}$

The above compound when introduced with nitrous acid, leads to the amine group being replaced by the hydroxyl functional group. The name of the compound after the reaction is ethyl alcohol. The product of the reaction matches with the product mentioned in question. Thus, our assumption was correct and the structure of 'A' is,
$C{{H}_{3}}N\equiv C$
When compound 'A' is reacted with chloroform and alcoholic KOH, carbylamine reaction takes place.
Therefore, the product of the reaction is $C{{H}_{3}}N\equiv C$.
So, the correct answer is “Option C”.

Note: Carbylamine reaction also known as Hofmann isocyanide synthesis is the synthesis of an isocyanide by the reaction of a primary amine with chloroform in presence of a base.
- The intermediate formed is dichlorocarbene.
- Carbylamine test is one of the confirmatory tests for primary amines, as only primary amine answers this test.