Coupling of benzene diazonium chloride and phenol to form p- hydroxy azobenzene (orange dye) is an example of

Options

A. elimination reaction
B. electrophilic substitution reaction
C. nucleophilic substitution reaction
D. electrophilic addition reaction

Answer

To solve the question regarding the coupling of benzene diazonium chloride and phenol to form p-hydroxy azobenzene, we can break down the process into clear steps.

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactants in this reaction are benzene diazonium chloride (C6H5N2Cl) and phenol (C6H5OH).

2. **Understand the Nature of Benzene Diazonium Chloride**:
- Benzene diazonium chloride is a weak electrophile. It contains a diazonium group (N2^+) that can participate in electrophilic substitution reactions.

3. **Recognize the Reactivity of Phenol**:
- Phenol is an activated aromatic compound due to the presence of the hydroxyl (-OH) group, which donates electron density to the aromatic ring. This makes the ring more reactive towards electrophiles.

4. **Electrophilic Substitution Mechanism**:
- In the presence of phenol, the benzene diazonium chloride acts as an electrophile and undergoes electrophilic substitution. The -OH group on phenol is ortho/para directing, which means that the substitution will primarily occur at the ortho or para positions relative to the -OH group.

5. **Formation of p-Hydroxy Azobenzene**:
- The reaction leads to the formation of p-hydroxy azobenzene (C6H4(OH)-N=N-C6H4), where the diazonium group is coupled to the para position of the phenol. This compound is known as an orange dye.

6. **Conclusion**:
- The overall reaction is an example of an electrophilic substitution reaction, specifically a coupling reaction between the diazonium compound and the activated aromatic ring of phenol.

### Final Answer:
The coupling of benzene diazonium chloride and phenol to form p-hydroxy azobenzene (orange dye) is an example of **electrophilic substitution reaction**.