Which of the following is the most reactive towards ring nitration ?

Options

A. Benzene
B. Mesitylene
C. Toluene
D. `m-` xylene

Explanation

To determine which of the given benzene derivatives is the most reactive towards ring nitration, we need to analyze the structures and the effects of substituents on the reactivity of the aromatic ring.

### Step-by-Step Solution:

1. **Understanding Nitration**: Nitration of benzene involves the substitution of a hydrogen atom on the benzene ring with a nitro group (NO2). This process is facilitated by the electrophile NO2+, which is generated from nitric acid (HNO3) in the presence of sulfuric acid (H2SO4).

2. **Identify the Compounds**: The compounds we are comparing are:
- A: Benzene
- B: Mesitylene (1,3,5-trimethylbenzene)
- C: Toluene (methylbenzene)
- D: Metaxylene (1,3-dimethylbenzene)

3. **Evaluate the Effects of Substituents**:
- **Benzene**: It has no substituents and serves as a baseline for reactivity.
- **Mesitylene**: Contains three methyl groups. Methyl groups are electron-donating through hyperconjugation and inductive effects, which stabilize the positive charge in the intermediate formed during electrophilic substitution. This increases the reactivity of the ring.
- **Toluene**: Has one methyl group, which also donates electrons but to a lesser extent than mesitylene.
- **Metaxylene**: Contains two methyl groups but they are positioned such that they provide less stabilization compared to the three methyl groups in mesitylene.

4. **Comparing Reactivity**:
- The more electron-donating groups attached to the benzene ring, the more reactive the ring will be towards electrophilic substitution reactions like nitration.
- Mesitylene, with three methyl groups, has the highest electron-donating effect due to hyperconjugation and inductive effects, making it the most reactive towards nitration.

5. **Conclusion**: Based on the analysis, mesitylene (1,3,5-trimethylbenzene) is the most reactive towards ring nitration among the given compounds.

### Final Answer:
**B: Mesitylene (1,3,5-trimethylbenzene)** is the most reactive towards ring nitration.