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 answer the question regarding the catalyst used in the preparation of chlorobenzene by the Gattermann reaction, we can break down the solution into clear steps:

### Step-by-Step Solution:

1. **Understanding the Gattermann Reaction**:
The Gattermann reaction is a method for the electrophilic substitution of halogens into aromatic compounds, particularly benzene derivatives. It involves the use of diazonium salts.

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

2. **Identifying the Reactants**:
In the Gattermann reaction, diazonium chloride (Ar-N2+ Cl-) is used along with a halogen source and a catalyst. The halogen source can be hydrochloric acid (HCl) or hydrobromic acid (HBr).

**Hint**: Remember that diazonium salts are key reactants in this reaction.

3. **Role of the Catalyst**:
The catalyst in the Gattermann reaction is typically copper (Cu). It facilitates the reaction by promoting the substitution of the diazonium group with a halogen atom.

**Hint**: Think about what substances are commonly used as catalysts in organic reactions, especially those involving halogenation.

4. **Reaction Mechanism**:
When copper is present, it helps in the release of nitrogen gas (N2) from the diazonium salt and allows the halogen (Cl or Br) to attach to the benzene ring, forming chlorobenzene or bromobenzene.

**Hint**: Consider how catalysts function by lowering the activation energy of a reaction.

5. **Conclusion**:
Therefore, the catalyst used in the preparation of chlorobenzene by the Gattermann reaction is copper.

**Hint**: Summarize your findings to reinforce the answer.

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