con. sulphuric acid & alkene

Alkenes react with concentrated sulphuric acid to form R-OSO3H. Most of the products are soluble in the unreacted sulphuric acid.

For example, ethene reacts concentrated sulphuric acid to give CH­3-CH2OSO3H. Equation :
CH2=CH2 + H2SO4 → CH3-CH2OSO3H

The π bond (the weaker bond of the double bond) of the alkene is broken and a C-C single bond. H2SO­4 was separated into two parts H+ and OSO3H-, and the two parts add separately to the two C atoms. This type of reaction is known as electrophilic addition.