Benzene on treatment with a mixture of conc. `HNO_(3)` and con. `H_(2)SO_(4)` at 373K gives

Options

A. Nitrobenzene
B. p-dinitrobenzene
C. o-dinitrobenzene
D. m-dinitrobenzene

Answer

To solve the question of what product is formed when benzene is treated with a mixture of concentrated nitric acid and concentrated sulfuric acid at 373 K, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reaction Conditions**:
- We are treating benzene with a mixture of concentrated nitric acid (HNO₃) and concentrated sulfuric acid (H₂SO₄) at a temperature of 373 K (approximately 100 °C).

2. **Understand the Nitration Process**:
- The combination of concentrated nitric acid and concentrated sulfuric acid generates the nitronium ion (NO₂⁺), which is the active electrophile in the nitration of benzene.

3. **Write the Reaction**:
- The reaction can be represented as:
\[ \text{C}_6\text{H}_6 + \text{NO}_2^+ \rightarrow \text{C}_6\text{H}_5\text{NO}_2 + \text{H}^+ \]
- Here, benzene (C₆H₆) reacts with the nitronium ion (NO₂⁺) to form nitrobenzene (C₆H₅NO₂).

4. **Determine the Major Product**:
- At lower temperatures (around 50-60 °C), the major product is nitrobenzene. However, at higher temperatures (373 K), the nitration leads to further substitution.
- The nitro group (–NO₂) is a meta-directing group, which means that if a second nitro group is introduced, it will preferentially go to the meta position relative to the first nitro group.

5. **Predict the Final Product**:
- At 373 K, the major product formed will be meta-dinitrobenzene (C₆H₄(NO₂)₂) due to the introduction of a second nitro group at the meta position.

### Final Answer:
- The product formed when benzene is treated with a mixture of concentrated nitric acid and concentrated sulfuric acid at 373 K is **meta-dinitrobenzene**.