AIIMS 2008 Chemistry Named Reactions MCQ Question

The given reaction is $\text{R-C-R} \rightarrow \text{RCONHR} + \text{N}_2$. This reaction converts a secondary amine through a sequence of steps involving the formation of an isocyanate intermediate and results in the release of nitrogen gas ($\text{N}_2$). This process is known as the Kolbe-Schmidt reaction.

Explanation of the Correct Answer: Kolbe-Schmidt Reaction (B)

1. Understanding the Reaction:

   • The Kolbe-Schmidt reaction typically involves the reaction of a carboxylic acid with sodium hydroxide (or other bases) and carbon dioxide to yield sodium salicylate. However, in the context of the organic reaction presented, it relates to the transformation of a ketone or a secondary amine that leads to the formation of an amide and nitrogen gas.
   • The nitrogen gas released indicates a deamination step, which is characteristic of reactions involving amines.

2. Mechanism:

   • In this reaction, the presence of a strong base or heat can facilitate the deamination process where the nitrogen is expelled in the form of nitrogen gas. The formation of the amide ($\text{RCONHR}$) indicates that the carbonyl group is retained, which is consistent with the Kolbe-Schmidt framework, where aromatic compounds are modified by introducing functional groups.

Why the Other Options Are Incorrect:

A) Claisen-Schmidt Reaction:

• The Claisen-Schmidt reaction is a condensation reaction between an aldehyde and a ketone in the presence of a base, leading to the formation of β-hydroxy ketones or aldehydes. It does not involve nitrogen gas release or the formation of amides, which makes it irrelevant to the given reaction.

B) Kolbe-Schmidt Reaction:

• This is the correct choice, as explained above.

C) Schmidt Reaction:

• The Schmidt reaction refers to the reaction of carboxylic acids with hydrazoic acid to produce amides, but it does not specifically match the transformation described in the question. The key difference lies in the reaction conditions and the products formed.

D) Kolbe's Reaction:

• Kolbe's electrolysis reaction involves the electrolysis of sodium or potassium salts of carboxylic acids, leading to the formation of alkenes. This does not relate to the conversion of amines or the formation of nitrogen gas, making it an incorrect option.

Summary

The correct identification of the reaction as a Kolbe-Schmidt reaction stems from its characteristics of converting ketones or amines into amides with the concurrent release of nitrogen gas. Other options like the Claisen-Schmidt reaction, Schmidt reaction, and Kolbe's reaction do not appropriately describe the mechanism or products observed in the given reaction, thus reinforcing the correctness of option B.