Answer the following questions: Write in brief about the reaction steps of the sulphonation reaction of benzene and its mechanism.

(N/A) The sulphonation of benzene involves the following steps:
$1$. Formation of the electrophile: $2 H_{2}SO_{4} \rightleftharpoons SO_{3} + HSO_{4}^{-} + H_{3}O^{+}$.
$2$. Formation of the $\sigma$-complex: The electrophile $SO_{3}$ attacks the benzene ring to form an unstable $\sigma$-complex (carbocation). This is the slow,rate-determining step.
$3$. Loss of proton: The $\sigma$-complex loses a proton to $HSO_{4}^{-}$ to form the benzene sulphonate ion $(C_{6}H_{5}SO_{3}^{-})$ and $H_{2}SO_{4}$.
$4$. Protonation: The benzene sulphonate ion accepts a proton from $H_{3}O^{+}$ to form benzene sulphonic acid $(C_{6}H_{5}SO_{3}H)$.