Nitration of benzene is carried out with conc. `HNO_(3)` in presence of conc. `H_(2)SO_(4)`. The role of conc. `H_(2)SO_(4)` is to provide

Options

A. nucleophile during the reaction
B. free radical during the reaction
C. electrophile during the reaction
D. catalyst during the reaction

Explanation

To solve the question regarding the role of concentrated sulfuric acid in the nitration of benzene, we can break down the process into several steps:

### Step 1: Generation of the Electrophile
- When concentrated nitric acid (HNO₃) is mixed with concentrated sulfuric acid (H₂SO₄), a chemical reaction occurs that generates the nitronium ion (NO₂⁺), which is the electrophile needed for the nitration of benzene.
- The reaction can be represented as:
\[ \text{HNO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{NO}_2^+ + \text{H}_3\text{O}^+ + 2 \text{HSO}_4^- \]
- Here, the nitronium ion (NO₂⁺) is the active electrophile that will attack the benzene ring.

### Step 2: Electrophilic Attack on Benzene
- The generated nitronium ion (NO₂⁺) acts as an electrophile and attacks the electron-rich benzene ring.
- This results in the formation of a sigma complex (also known as an arenium ion), which can be represented as follows:
\[ \text{C}_6\text{H}_5 + \text{NO}_2^+ \rightarrow \text{C}_6\text{H}_5\text{NO}_2^+ \]
- The benzene ring undergoes a temporary disruption of its aromaticity due to the formation of the sigma complex.

### Step 3: Deprotonation and Restoration of Aromaticity
- The sigma complex then loses a proton (H⁺) to restore aromaticity, which is facilitated by the bisulfate ion (HSO₄⁻) generated during the electrophile generation.
- The reaction can be summarized as:
\[ \text{C}_6\text{H}_5\text{NO}_2^+ \rightarrow \text{C}_6\text{H}_5\text{NO}_2 + \text{H}^+ \]
- The final product of this reaction is nitrobenzene (C₆H₅NO₂).

### Conclusion: Role of Concentrated Sulfuric Acid
- The concentrated sulfuric acid acts as a catalyst in this reaction. It is not consumed in the reaction but facilitates the generation of the nitronium ion, which is essential for the nitration process. After the reaction, the sulfuric acid is regenerated.

### Final Answer
The role of concentrated sulfuric acid in the nitration of benzene is to provide the nitronium ion (NO₂⁺) as an electrophile and to act as a catalyst.

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