Question

How many transition states are there in the mechanism for the acid-catalyzed hydration of an alkene?

Answer 1

There are three transition states in the mechanism for the acid-catalyzed hydration of an alkene.

The acid-catalyzed hydration has three steps:

1. Protonation of the alkene by hydronium ion (addition of the electrophile).
2. Addition of water to the carbocation (addition of the nucleophile).
3. Deprotonation of the oxonium ion.

Each step has its own transition state. You can see these as three peaks in the energy profile diagram below.

The video below explains the mechanism for acid-catalyzed hydration of an alkene.