Reaction ofbenzenediazonium chloride with alkaline b - napthol gives an azo dye. This is an example of

Options

A. Electrophilic substitution
B. Nucleophilic substitution
C. Oxidative coupling
D. A free radical reaction

Answer

To solve the question regarding the reaction of benzenediazonium chloride with alkaline beta-naphthol resulting in the formation of an azo dye, we can break down the process step by step.

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactants are benzenediazonium chloride (C6H5N2Cl) and alkaline beta-naphthol (C10H7OH).
- Benzenediazonium chloride contains a diazonium group (N2+), which is a good electrophile.

**Hint**: Recognize the functional groups in the reactants. The diazonium group is key for electrophilic reactions.

2. **Understand the Reaction Type**:
- The reaction is a type of electrophilic substitution. The diazonium ion acts as an electrophile and reacts with the nucleophilic site on beta-naphthol, which has an -OH group that can donate electrons.

**Hint**: Recall that electrophiles seek electrons and nucleophiles donate electrons. Identify which species is which.

3. **Mechanism of Reaction**:
- The -OH group on beta-naphthol increases the electron density on the aromatic ring, making it more reactive towards electrophiles.
- The lone pair of electrons from the -OH group attacks the positively charged nitrogen in the diazonium ion, leading to the formation of a new bond.

**Hint**: Visualize the movement of electrons. Use curved arrows to show the donation of electrons from the nucleophile to the electrophile.

4. **Formation of Azo Compound**:
- After the nucleophilic attack, a bond forms between the beta-naphthol and the diazonium ion, resulting in the formation of an azo compound (C6H5-N=N-C10H7).
- A proton (H+) is eliminated during the reaction, stabilizing the newly formed azo bond.

**Hint**: Remember that the azo bond (N=N) is characteristic of azo dyes.

5. **Final Product**:
- The final product is an azo dye, which is a compound containing the -N=N- linkage, and is often brightly colored, making it useful in dyeing textiles.

**Hint**: Azo dyes are known for their vivid colors due to the extended conjugation in their structure.

### Conclusion:
The reaction of benzenediazonium chloride with alkaline beta-naphthol to form an azo dye is an example of electrophilic substitution, where the diazonium ion acts as an electrophile and beta-naphthol acts as a nucleophile.