Final answer:
Acid catalyzed hydration of alkenes proceeds by protonation of the alkene to form a carbocation, followed by water acting as a nucleophile to form the intermediate, and finally deprotonation to yield an alcohol. Sulfuric acid is a common catalyst due to its weakly nucleophilic conjugate base.
Step-by-step explanation:
Acid catalyzed hydration of alkenes typically proceeds through a three-step mechanism. In the first step, the alkene is protonated by the acid, leading to the formation of a carbocation intermediate. This step is followed by the addition of water where H₂O acts as a nucleophile and attacks the carbocation, forming an alcohol with an attached proton. In the final step, deprotonation occurs when another water molecule removes the excess proton, thus generating the alcohol as the final product. Sulfuric acid (H₂SO₄) is often used as the acid catalyst because its conjugate base, HSO₄⁻, is a poor nucleophile. Despite H₂O also being a poor nucleophile, its high concentration in the reaction mixture allows it to compete successfully in the nucleophilic attack.
The formation of ethanol from ethylene in the presence of water and a strong acid catalyst like sulfuric acid is a common example of hydration.