The Hydration of Alkenes
When alkenes are treated with certain aqueous acids (usually sulfuric acid), the resulting electrophilic addition reaction yields an alcohol as the product. The regioselectivity of such reactions can be predicted by Markownikoff’s rule. Therefore, these reactions can be classified as Markovnikov reactions. In the hydration of alkenes, the H+ ion acts as an electrophile and attacks the alkene to generate a carbocation intermediate (the intermediate with greater stability is protonated). The subsequent nucleophilic attack on the carbocation by water molecules forms an oxonium ion, which is deprotonated to afford the required alcohol product.