How do alkenes react with sulphuric acid? Discuss its mechanism.

Alkenes react with the sulphuric acid in cold to form alkyl hydrogen sulphates. The addition in case of unsymmetrical alkenes proceeds according to Markownikov's rule. 



Mechanism: It involves electrophilic addition reaction and consists of the following two steps:

(i) Electromeric effect and electrophilic attack:





(ii) Attack of nucleophile: The nucleophile released in the slow step combines with carbocation to give ethyl hydrogen sulphate.