Which of the following would be most reactive towards nitration

Options

A. Benzene
B. Nitro benzene
C. Toluene
D. Chloro benzene

Explanation

To determine which compound is most reactive towards nitration, we need to analyze the electron density of each compound's benzene ring. Nitration is an electrophilic substitution reaction, and the reactivity of the aromatic compounds towards nitration depends on the electron-donating or electron-withdrawing effects of substituents on the benzene ring.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds we are considering are:
- Benzene
- Nitrobenzene
- Toluene
- Chlorobenzene

2. **Understand Nitration**: Nitration involves the substitution of a hydrogen atom on the benzene ring with a nitro group (NO2). The reaction is facilitated by the presence of an electrophile, which in this case is the nitronium ion (NO2+).

3. **Assess Electron Density**: The reactivity of the benzene ring towards nitration is influenced by the electron density:
- **Benzene**: Neutral, no electron-donating or withdrawing groups.
- **Nitrobenzene**: Contains a nitro group (-NO2), which is a strong electron-withdrawing group. This decreases the electron density of the ring, making it less reactive towards nitration.
- **Toluene**: Contains a methyl group (-CH3), which is an electron-donating group (+I effect). This increases the electron density of the benzene ring, making it more reactive towards nitration.
- **Chlorobenzene**: Contains a chlorine atom (-Cl), which has a -I effect (electron-withdrawing) but also has a +R effect (resonance donation). However, the -I effect is stronger, making the ring less reactive than toluene.

4. **Compare Reactivity**:
- Nitrobenzene is the least reactive due to the strong electron-withdrawing effect of the nitro group.
- Chlorobenzene is less reactive than benzene due to the -I effect of chlorine.
- Toluene is more reactive than benzene because of the electron-donating effect of the methyl group.

5. **Conclusion**: Among the given compounds, toluene is the most reactive towards nitration due to its increased electron density from the methyl group.

### Final Answer:
**Toluene is the most reactive towards nitration.**