Hydration of alkenes

Water can be added to an alkene in the presence of an acid catalyst, to produce an alcohol.

Water is not a strong enough electrophile to add an H⁺ directly to an alkene, but H₃O⁺ is.  The H₃O⁺ is. formed when sulfuric acid dissociates in water:

The alkene then reacts with the H₃O⁺ in the electrophilic addition elementary step.  The resultant carbocation is reactive, and water then easily reacts as a nucleophile to perform the coordination step.  A final acid-base step, regenerating the H₃O⁺ catalyst, produces the alcohol product.