Which of the following reactions is not an example of electrophilic substitution in benzene ring?

Options

A.
B.
C.
D.

Explanation

To determine which of the following reactions is not an example of electrophilic substitution in the benzene ring, we will analyze each option step by step.

### Step 1: Understanding Electrophilic Substitution
Electrophilic substitution reactions in benzene involve the replacement of a hydrogen atom on the benzene ring with an electrophile. The general mechanism involves the formation of a sigma complex (arenium ion) followed by deprotonation to restore aromaticity.

### Step 2: Analyze Each Reaction

1. **Option A: Chlorination of Benzene**
- Reaction: Benzene + Cl₂ (in presence of AlCl₃)
- Mechanism: AlCl₃ activates Cl₂ to generate Cl⁺, which acts as an electrophile. Cl⁺ substitutes a hydrogen atom on the benzene ring, forming chlorobenzene and HCl.
- Conclusion: This is an electrophilic substitution reaction.

2. **Option B: Acylation of Benzene**
- Reaction: Benzene + CH₃C(=O)Cl (in presence of AlCl₃)
- Mechanism: AlCl₃ activates the acyl chloride to generate an acylium ion (CH₃C⁺(=O)). This acylium ion substitutes a hydrogen atom on the benzene ring, forming an acylated product.
- Conclusion: This is also an electrophilic substitution reaction (Friedel-Crafts acylation).

3. **Option C: Addition of Chlorine to Benzene**
- Reaction: Benzene + Cl₂ (in presence of sunlight)
- Mechanism: In the presence of light, Cl₂ undergoes homolytic cleavage to form Cl• radicals. These radicals add across the double bonds of benzene, leading to the formation of benzene hexachloride (BHC).
- Conclusion: This is not an electrophilic substitution; it is an addition reaction.

4. **Option D: Sulfonation of Benzene**
- Reaction: Benzene + SO₃ (in presence of H₂SO₄)
- Mechanism: SO₃ generates the electrophile (SO₃H⁺), which substitutes a hydrogen atom on the benzene ring, forming benzenesulfonic acid.
- Conclusion: This is an electrophilic substitution reaction.

### Final Conclusion
After analyzing all options, **Option C** (Addition of Chlorine to Benzene) is not an example of electrophilic substitution in the benzene ring.

### Answer: Option C is the correct answer.

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