Question

Arrange the following reaction mechanism of sulphonation of benzene

• A. $\mathrm{Formation}\mathrm{of}\mathrm{Arenium}\mathrm{ion}$
• B. $\mathrm{Formation}\mathrm{of}\mathrm{electrophile}$
• C. $\mathrm{Formation}\mathrm{of}\mathrm{benzene}\mathrm{sulphonate}\mathrm{anion}$
• D. $\mathrm{Formation}\mathrm{of}\mathrm{benzene}\mathrm{sulphonic}\mathrm{acid}$

Answer 1

1. In step one two molecules of $H_{2}S{O}_4$ acts as both acid and base and $S{O}_3$ if formed ia electrophile.
2. In step two $S{O}_3$ reacts with benzene and arenium ion is formed.
3. In step three base abstracts the proton from arenium ion and benzene sulphonate anion is formed.
4. In step four this anion accepts proton and the bezene sulphonic acid is formed.