During coupling reaction of benzene diazonium chloride and aniline, the pH of reaction medium should be approximately

Options

A. `1-2`
B. `9-10`
C. `4-5`
D. `7-8`

Answer

To determine the appropriate pH for the coupling reaction of benzene diazonium chloride and aniline, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactants in this coupling reaction are benzene diazonium chloride (C6H5N2Cl) and aniline (C6H5NH2).

2. **Understand the Nature of Aniline**:
- Aniline is a basic compound due to the presence of the amino group (-NH2), which can accept protons (H+).

3. **Recognize the Reaction Type**:
- The reaction between benzene diazonium chloride and aniline is a coupling reaction that forms an azo compound. In this case, the product is p-aminoazobenzene (C6H5-N=N-C6H4-NH2).

4. **Determine the pH Requirement**:
- For the coupling reaction to proceed effectively, the pH of the reaction medium should not be too acidic or too basic.
- If the medium is too acidic (low pH), aniline would be protonated, which would hinder its nucleophilic attack on the diazonium salt.
- If the medium is too basic (high pH), the reaction may not favor the formation of the desired product.

5. **Optimal pH Range**:
- The optimal pH range for this reaction is approximately 4 to 5. This moderate acidic environment allows aniline to remain in its basic form without being excessively protonated, thus facilitating the coupling reaction.

6. **Conclusion**:
- Therefore, the pH of the reaction medium should be approximately 4 to 5 for the coupling reaction of benzene diazonium chloride and aniline to occur efficiently.

### Final Answer:
The pH of the reaction medium should be approximately **4 to 5**.

---