The attacking reagent in electrophilic sulphonation of benzene is

Options

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

Answer

B

Explanation

Mechanism for sulphonation of benzene
Step I :
The Pi electrons of aromatic C=C act as a nucleophile, attacking the electrophilic , S pushing charge out onto an electronegative oxygen atom. This destroys the aromaticity giving the cyclohexadienyl cation intermediate

Step II :
Loss of the proton from the `sp^3` carbon bearing the sulphonyl – group reforms the C=C and the aromatic system

Step III :
Protonation of the conjugate base of the sulphonic acid by sulphuric acid produces the sulphonic acid.