The Hunsdieckers reaction is a chemical reaction that involves the conversion of a carboxylic acid into its corresponding alkyl halide. This reaction is named after the German chemists Heinz Hunsdiecker and Heinz Hunsdiecker.

The correct answer to the question is option 'A' - "Only Cl2 can give alkyl halide." This statement is incorrect because both Cl2 and Br2 can be used in the Hunsdieckers reaction to form alkyl halides.

Explanation:

1. Overview of the Hunsdieckers reaction:
The Hunsdieckers reaction involves the conversion of a carboxylic acid (R-COOH) into its corresponding alkyl halide (R-X). The reaction proceeds through the formation of a silver carboxylate intermediate, which then undergoes homolytic cleavage to form a carboxyl radical (R•) and a silver halide (AgX). The carboxyl radical can then abstract a halogen atom from a halogen molecule (X2) to form the alkyl halide.

2. Role of different halogens:
- Chlorine (Cl2): Cl2 is commonly used in the Hunsdieckers reaction to convert carboxylic acids into alkyl chlorides. The reaction proceeds through the formation of a silver carboxylate intermediate, which then undergoes homolytic cleavage to form a carboxyl radical and silver chloride (AgCl). The carboxyl radical can then abstract a chlorine atom from another Cl2 molecule to form the alkyl chloride (R-Cl).

- Bromine (Br2): Br2 can also be used in the Hunsdieckers reaction to convert carboxylic acids into alkyl bromides. The reaction mechanism is similar to that with chlorine, where a silver carboxylate intermediate is formed, followed by homolytic cleavage to form a carboxyl radical and silver bromide (AgBr). The carboxyl radical can then abstract a bromine atom from another Br2 molecule to form the alkyl bromide (R-Br).

- Iodine (I2): In the Hunsdieckers reaction, iodine (I2) does not give an alkyl halide. Instead, when treated with silver carboxylate, it forms an ester. This is known as the Hunsdieckers ester synthesis. The reaction proceeds through the formation of a silver carboxylate intermediate, followed by homolytic cleavage to form a carboxyl radical and silver iodide (AgI). The carboxyl radical can then abstract an iodine atom from another I2 molecule to form the alkyl iodide, which undergoes further reaction to form the ester.

3. Reaction mechanism:
The Hunsdieckers reaction proceeds through a free radical mechanism. The silver carboxylate intermediate undergoes homolytic cleavage to form a carboxyl radical and a silver halide. The carboxyl radical can then abstract a halogen atom from another halogen molecule to form the alkyl halide. This mechanism involves the generation and propagation of free radicals.

In conclusion, option 'A' is incorrect because both Cl2 and Br2 can be used in the Hunsdieckers reaction to form alkyl halides. The reaction proceeds through a free radical mechanism, and