Nitration of benzene is

Options

A. nucleophilic substitution
B. nucleophilic addition
C. electrophilic substitution
D. free radical substitution.

Explanation

To solve the question regarding the nitration of benzene, we will follow a step-by-step approach to understand the mechanism and identify the correct answer from the given options.

### Step 1: Understand the Reaction
Nitration of benzene involves the introduction of a nitro group (NO2) into the benzene ring. The reaction is typically carried out using a nitrating mixture of concentrated nitric acid (HNO3) and concentrated sulfuric acid (H2SO4).

### Step 2: Identify the Mechanism
The key to determining the type of reaction is to identify the mechanism involved. The options provided are:
- Nucleophilic substitution
- Nucleophilic addition
- Electrophilic substitution
- Free radical substitution

### Step 3: Formation of the Electrophile
In the nitration process, the first step is the formation of the nitronium ion (NO2+), which acts as the electrophile. This is formed from the reaction of nitric acid and sulfuric acid:
- HNO3 + H2SO4 → NO2+ + HSO4- + H2O

The nitronium ion is electron-deficient and is capable of attacking the electron-rich benzene ring.

### Step 4: Electrophilic Attack
The nitronium ion (NO2+) attacks the benzene ring. The π electrons of the benzene ring react with the nitronium ion, leading to the formation of a carbocation intermediate known as the sigma complex or arenium ion.

### Step 5: Deprotonation
In the final step, the carbocation loses a proton (H+) to restore the aromaticity of the benzene ring. The proton is abstracted by the bisulfate ion (HSO4-) formed earlier in the reaction, resulting in the formation of nitrobenzene (C6H5NO2) and regenerating sulfuric acid (H2SO4).

### Conclusion
Since the reaction involves the substitution of a hydrogen atom in the benzene ring by a nitro group, and the mechanism involves an electrophile attacking the benzene, the correct answer to the question "Nitration of benzene is" is:

**Electrophilic substitution (Option C)**.

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