Question

Identify the product (P) in the following reaction:

• A.

  

• B.

  

• C.

  

• D.

  

Answer 1

The Correct Option is A

To identify product (P) of the given reaction, analyze reaction conditions and reactants.

1. The starting material is a cyclic carboxylic acid, as depicted in the provided image.
2. The reaction sequence, \({\text{Br}_2/\text{Red P}}\) followed by hydrolysis (\({\text{H}_2\text{O}}\)), is indicative of the Hell-Volhard-Zelinsky (HVZ) reaction, used for α-bromination of carboxylic acids.
3. Within the HVZ reaction:
   • \({\text{Br}_2}\) and red phosphorus (Red P) generate \({\text{PBr}_3}\), a brominating agent.
   • The carboxylic acid is converted to an acyl bromide intermediate, which then undergoes α-halogenation.
   • Hydrolysis with water reforms the carboxylic acid functional group, incorporating a bromine atom at the α-position.
4. Consequently, product (P) will be the original cyclic carboxylic acid with a bromine atom substituted at the α-carbon, adjacent to the carboxyl group.
5. Referring to the provided options, the correct structure for the α-brominated product is illustrated in the following figure:

This selection accurately represents the cyclic structure with an α-carbon bromination, aligning with the established reaction mechanism.