Reaction of benzenediazonium 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 β-naphthol leading to the formation of an azo dye, we can follow these steps:

### Step 1: Identify the Reaction
The reaction in question involves benzenediazonium chloride (C6H5N2Cl) and alkaline β-naphthol (C10H7OH). This is a classic example of azo coupling, where a diazonium compound reacts with an aromatic compound.

**Hint:** Look for the presence of a diazonium compound and an aromatic compound in the reaction.

### Step 2: Understand Azo Coupling
Azo coupling is a reaction where a diazonium salt reacts with an activated aromatic compound. In this case, the diazonium ion (C6H5N2+) acts as an electrophile, while β-naphthol, which has a hydroxyl (-OH) group, acts as a nucleophile.

**Hint:** Remember that in azo coupling, the diazonium ion is an electrophile that substitutes onto the aromatic compound.

### Step 3: Reaction Mechanism
The mechanism involves the electrophilic substitution of the diazonium ion onto the β-naphthol. The hydroxyl group on β-naphthol is ortho- and para-directing, which means the substitution will occur at the para position relative to the hydroxyl group.

1. The diazonium ion (C6H5N2+) attacks the para position of β-naphthol.
2. This results in the formation of an azo compound (C6H5-N=N-C10H7) and the elimination of HCl.

**Hint:** Focus on the positions where substitution occurs due to directing effects of substituents.

### Step 4: Identify the Type of Reaction
The overall reaction can be classified as an electrophilic aromatic substitution reaction because:
- An electrophile (the diazonium ion) substitutes for a hydrogen atom on the aromatic ring of β-naphthol.

**Hint:** Recall that electrophilic aromatic substitution involves the replacement of a hydrogen atom on an aromatic ring by an electrophile.

### Step 5: Conclusion
Based on the analysis, the reaction of benzenediazonium chloride with alkaline β-naphthol to form an azo dye is an example of an **electrophilic aromatic substitution reaction**.

**Final Answer:** The reaction is an example of electrophilic aromatic substitution.