Explain the mechanism of sulphonation of benzene?

Explanation

Sulphonation : Benzene reacts with concentrated sulphuric acid at `80^(@)`C to form benzene sulphuric acid.

Mechanism: This involves the following steps.
Step 1: Generation of electrophile `SO_(3)`
`" "2H_(2)SO_(4) hArr SO_(3) + H_(3)O^(+) + HSO_(4)^(-)`
Step 2: The electrophile `SO_(3)` attacks the benzene ring to form a carbocation which is resonance stabilized.

Step 3: Loss of a proton to give introbenzene. The proton is removed by `HSO_(4)^(-)`

Step 4: Addition of proton to give benzene sulphonic acid.