Question

Is acid-catalyzed hydration stereoselective?

Answer 1

Acid-catalyzed hydration of alkenes is not stereoselective.

The steps in the mechanism are:

1. Protonation of the π bond to form a carbocation
2. Addition of water to the carbocation to form an oxonium ion
3. Deprotonation of the oxonium ion to form an alcohol.

This carbocation formed in Step 1 is `sp^2` hybridized. It is planar, so it can react with a water molecule on either the top or the bottom face.

That means that the reaction is not stereoselective.

If the carbon bearing the OH group is chiral, we get a mixture of (R) and (S) alcohols.