$RNH_{2}+CHCl_{3}+KOH\xrightarrow{\Delta}?$ The product of above reaction is :

Question

Accepted Answer

The reaction in question is known as the Hofmann rearrangement or Hofmann degradation. This reaction involves the conversion of a primary amine (RNH₂) into an isocyanide (RNC) when treated with chloroform (CHCl₃) and a strong base like potassium hydroxide (KOH) under heating (Δ).

1. **Explanation for Option 4 (RNC):**
   - In the Hofmann rearrangement, the primary amine reacts with chloroform in the presence of a strong base. The base deprotonates the amine, forming an anion that facilitates the nucleophilic attack on chloroform. This leads to the formation of dichlorocarbene (CCl₂), which is highly reactive.
   - The dichlorocarbene then inserts into the nitrogen of the amine, leading to the formation of an isocyanide (RNC) as the final product. This is a well-documented transformation in organic chemistry, and the conditions described in the question are typical for this reaction.

2. **Explanation for why other options are incorrect:**
   - **Option 1 (RCl):** This option suggests the formation of an alkyl chloride. However, the reaction conditions and reagents (CHCl₃ and KOH) do not favor the formation of RCl from a primary amine. There is no mechanism in this reaction setup that would lead to the substitution of the amine group with a chlorine atom.
   - **Option 2 (ROH):** This option suggests the formation of an alcohol. The reaction conditions do not involve any oxidizing agents or pathways that would convert an amine to an alcohol. The presence of chloroform and a strong base does not facilitate such a transformation.
   - **Option 3 (RCN):** This option suggests the formation of a nitrile. While nitriles can be formed from amines through other reactions, the Hofmann rearrangement specifically leads to the formation of isocyanides (RNC), not nitriles (RCN). The reaction mechanism and intermediates involved do not support the formation of a nitrile under these conditions.

In conclusion, the reaction of a primary amine with chloroform and potassium hydroxide under heat specifically leads to the formation of an isocyanide (RNC), making Option 4 the correct answer.