The catalyst used in the preparation of chlorobenzene by Gattermann reaction is?

Options

A. `CuCl_(2)`
B. `Cu_(2)Cl_(2)`
C. Cu
D. `CuSO_(4)`

Answer

To solve the question regarding the catalyst used in the preparation of chlorobenzene by the Gattermann reaction, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Gattermann Reaction**:
The Gattermann reaction is a method used to introduce halogens (like chlorine or bromine) into an aromatic ring, such as benzene. This reaction involves the use of diazonium salts and is typically performed in the presence of a catalyst.

**Hint**: Recall that the Gattermann reaction is specifically for introducing halogens into aromatic compounds.

2. **Identify the Reactants**:
The general reaction can be represented as:
\[ \text{ArN}_2^+ + \text{X}^- \xrightarrow{\text{Cu, HCl}} \text{ArX} + \text{N}_2 + \text{CuX} \]
Here, Ar represents the aryl group (like benzene), N₂ is nitrogen gas, and X can be Cl or Br.

**Hint**: Remember that the diazonium salt (ArN₂⁺) is a key intermediate in this reaction.

3. **Determine the Role of the Catalyst**:
In the Gattermann reaction, copper powder (Cu) acts as the catalyst. It facilitates the reaction between the diazonium salt and the halogen (Cl or Br) in the presence of hydrochloric acid (HCl).

**Hint**: Focus on the fact that copper is being used to promote the reaction without being consumed in the process.

4. **Conclusion**:
Based on the understanding of the Gattermann reaction and the role of copper as a catalyst, we can conclude that the catalyst used in the preparation of chlorobenzene by the Gattermann reaction is copper powder (Cu).

**Final Answer**: The catalyst used in the preparation of chlorobenzene by the Gattermann reaction is **copper powder (Cu)**.

### Summary of Steps:
- Understand the Gattermann reaction.
- Identify the reactants involved.
- Determine the role of the catalyst.
- Conclude with the answer.