Which of the following species participate in sulphonation of benzene ring ?

Options

A. `H_(2)SO_(4)`
B. `SO_(3)`
C. `HSO_(3)^(-)`
D. `SO_(2)^(-)`

Explanation

To determine which species participate in the sulfonation of the benzene ring, we need to analyze the process step by step.

### Step-by-Step Solution:

1. **Understanding Sulfonation**:
Sulfonation of benzene involves the introduction of a sulfonyl group (–SO3H) into the benzene ring. This reaction typically uses concentrated sulfuric acid (H2SO4) or sulfur trioxide (SO3).

2. **Identifying the Species**:
The options provided are:
- H2SO4
- SO3
- HSO3^-
- SO2^-

3. **Mechanism of Sulfonation**:
- When concentrated sulfuric acid (H2SO4) is used, it can produce sulfur trioxide (SO3) and bisulfate (HSO4^-) ions. The reaction can be summarized as:
\[ H2SO4 \rightarrow SO3 + HSO4^- \]
- In this process, SO3 acts as the electrophile that attacks the electron-rich benzene ring.

4. **Electrophilic Attack**:
- The benzene ring, being nucleophilic due to its high electron density, attacks the electrophilic sulfur in SO3. This leads to the formation of a sigma complex (an arenium ion).

5. **Restoration of Aromaticity**:
- The sigma complex rearranges, and the aromaticity of the benzene ring is restored by the loss of a proton (H^+), which can be taken up by the bisulfate ion (HSO4^-) or another base present in the solution.

6. **Final Product**:
- The final product of the reaction is benzene sulfonic acid (C6H5SO3H).

7. **Conclusion**:
- Among the given options, SO3 is the species that directly participates in the sulfonation of the benzene ring. H2SO4 is a source of SO3 but does not participate directly. HSO3^- and SO2^- do not participate in this reaction.

### Answer:
The species that participates in the sulfonation of the benzene ring is **SO3**.