Which of the following benzene ring has greater electron density than Toulene

Options

A.
B.
C.
D.

Answer

To determine which benzene ring has greater electron density than toluene, we need to analyze the substituents on the benzene rings in the given options. Toluene has a methyl group (-CH₃) attached to the benzene ring, which provides electron density through both hyperconjugation and inductive effects.

### Step-by-Step Solution:

1. **Identify the Structure of Toluene**:
- Toluene consists of a benzene ring with a methyl group (-CH₃) attached. The methyl group donates electron density to the benzene ring through:
- **+I Effect**: Inductive effect, where the methyl group pushes electrons towards the ring.
- **Hyperconjugation**: Stabilization due to the overlap of σ-bonds with the π-system of the benzene ring.

2. **Analyze Each Option**:
- **Option A: Benzaldehyde (C₆H₅CHO)**:
- The -CHO group has a **-I effect** (pulls electrons away) and a **-M effect** (resonance effect that also pulls electrons away). Thus, it decreases the electron density on the benzene ring compared to toluene.

- **Option B: Chlorobenzene (C₆H₅Cl)**:
- The chlorine atom exhibits a **-I effect** (pulls electrons away) and a **+R effect** (donates electrons through resonance). However, the -I effect is stronger than the +R effect in this case, leading to a net decrease in electron density compared to toluene.

- **Option C: Aniline (C₆H₅NH₂)**:
- The -NH₂ group has a **+R effect** (donates electrons through resonance) and a **-I effect** (pulls electrons away). The +R effect is stronger than the -I effect, resulting in an increase in electron density on the benzene ring compared to toluene.

- **Option D: Benzene (C₆H₆)**:
- Benzene has no substituents that provide electron-donating effects. It has a neutral electron density, which is less than that of toluene.

3. **Conclusion**:
- The only substituent that increases the electron density on the benzene ring compared to toluene is the -NH₂ group in aniline. Therefore, the correct answer is **Option C: Aniline**.