Reaction of `SO_(3)` is faster in :

Options

A. Benzene
B. Toluene
C. Nitrobenzene
D. chlorobenzene

Answer

To determine which compound will react faster with `SO₃` in electrophilic aromatic substitution (sulfonation), we need to analyze the substituents on the aromatic compounds provided in the options: benzene, toluene, nitrobenzene, and chlorobenzene.

### Step-by-Step Solution:

1. **Understanding Electrophilic Aromatic Substitution (EAS)**:
- In EAS, an electrophile (in this case, `SO₃`) attacks the aromatic ring. The rate of this reaction depends on the electron density of the ring, which is influenced by substituents attached to it.

2. **Identify the Nature of Substituents**:
- **Benzene**: No substituents, serves as a reference compound.
- **Toluene (C₆H₅-CH₃)**: The methyl group (CH₃) is an electron-donating group (EDG) through hyperconjugation and inductive effects, which increases the electron density on the aromatic ring.
- **Nitrobenzene (C₆H₅-NO₂)**: The nitro group (NO₂) is an electron-withdrawing group (EWG), which decreases the electron density on the aromatic ring, making it less reactive towards electrophiles.
- **Chlorobenzene (C₆H₅-Cl)**: The chlorine atom has both -I (inductive electron-withdrawing) and +M (mesomeric electron-donating) effects. However, the -I effect is stronger, leading to an overall decrease in electron density.

3. **Comparing Reactivity**:
- **Toluene**: The methyl group increases the electron density, making the ring more reactive towards electrophiles like `SO₃`.
- **Benzene**: Acts as a baseline; it has moderate reactivity.
- **Nitrobenzene**: Deactivates the ring due to the electron-withdrawing nature of the nitro group.
- **Chlorobenzene**: While it has some electron-donating character, the overall effect is still a decrease in electron density due to the stronger -I effect.

4. **Conclusion**:
- Among the options, toluene has the highest electron density due to the presence of the methyl group, making it the most reactive towards `SO₃`. Therefore, the reaction of `SO₃` is fastest in **toluene**.

### Final Answer:
The reaction of `SO₃` is faster in **toluene**.