In the nitration of benzene using a mixture of conc. `H_(2)SO_(4)` and conc. `HNO_(3)`, the species which initiates the reaction is __________.

Options

A. `NO_(2)`
B. `NO^(+)`
C. `NO_(2)^(+)`
D. `NO_(2)^(-)`

Explanation

To determine the species that initiates the nitration of benzene using a mixture of concentrated sulfuric acid (H₂SO₄) and concentrated nitric acid (HNO₃), we can follow these steps:

### Step 1: Understand the Role of the Acids
In the nitration reaction, concentrated sulfuric acid acts as a catalyst and helps generate the nitronium ion (NO₂⁺), which is the active electrophile that will react with benzene.

**Hint:** Remember that sulfuric acid is a strong acid and can donate protons (H⁺).

### Step 2: Formation of the Electrophile
When concentrated sulfuric acid and concentrated nitric acid are mixed, sulfuric acid donates a proton (H⁺) to nitric acid. This protonation of nitric acid leads to the formation of the nitronium ion (NO₂⁺) as follows:

1. H₂SO₄ → H⁺ + HSO₄⁻
2. HNO₃ + H⁺ → NO₂⁺ + H₂O

The nitronium ion (NO₂⁺) is formed as a result of this reaction.

**Hint:** Look for the species that is positively charged and has a nitrogen atom bonded to two oxygen atoms.

### Step 3: Identify the Initiating Species
The nitronium ion (NO₂⁺) is the species that initiates the nitration of benzene. It acts as an electrophile that will react with the electron-rich benzene ring.

**Hint:** The species that can attack the electron-rich benzene is typically a positively charged ion.

### Conclusion
The species which initiates the nitration of benzene using a mixture of concentrated H₂SO₄ and HNO₃ is the nitronium ion (NO₂⁺).

### Final Answer
The species which initiates the reaction is **NO₂⁺ (nitronium ion)**.