Sulphonation of benzene with excess sulphuric acid provides

Options

A. benzenesulphonic acid
B. p-benzenedisulphonic acid
C. o-benzenedisulphonic acid
D. m-benzenedisulphonic acid

Explanation

To solve the question regarding the sulphonation of benzene with excess sulfuric acid, we can break down the process into several steps:

### Step-by-Step Solution:

1. **Understanding Sulphonation**:
Sulphonation is the process of introducing a sulfonyl group (–SO3H) into an aromatic compound, in this case, benzene. This reaction typically occurs when benzene is treated with concentrated sulfuric acid (H2SO4).

2. **Formation of Electrophile**:
In the presence of excess sulfuric acid, sulfur trioxide (SO3) is generated. This SO3 acts as the electrophile in the reaction. The reaction can be represented as:
\[ H_2SO_4 \rightarrow H^+ + HSO_4^- \]
The HSO4^- can further react to form SO3.

3. **Electrophilic Attack**:
Benzene, which has a high electron density due to its π-bonds, acts as a nucleophile. The π-electrons of benzene attack the electrophile (SO3), leading to the formation of benzene sulfonic acid (C6H5SO3H). The reaction can be summarized as:
\[ C_6H_6 + SO_3 \rightarrow C_6H_5SO_3H \]

4. **Formation of Benzene Sulfonic Acid**:
The product formed from the reaction is benzene sulfonic acid, which has the structure C6H5SO3H. This compound features a sulfonic acid group (–SO3H) attached to the benzene ring.

5. **Effect of Excess Sulfuric Acid**:
Since sulfuric acid is in excess, it can lead to further sulphonation. The sulfonic acid group (–SO3H) is an electron-withdrawing group, which affects the reactivity of the benzene ring. It directs further electrophilic substitutions to the meta position due to decreased electron density at the ortho and para positions.

6. **Final Product**:
The final product of the sulphonation of benzene with excess sulfuric acid is benzene sulfonic acid (C6H5SO3H). If further sulphonation occurs, it can lead to disulfonic acids, but the primary product is benzene sulfonic acid.

### Summary:
The sulphonation of benzene with excess sulfuric acid primarily yields benzene sulfonic acid (C6H5SO3H).

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