Acid-catalysed hydration: practice and mechanism
Under acid catalysis the more stable carbocation forms and water attacks there: the OH group sits on the more substituted carbon (Markovnikov).
Example
The proton adds so that the more stable carbocation forms; water attacks there. The OH group ends up on the more substituted carbon (Markovnikov).
Mechanism step by step
- 1
H₃O⁺ protonates the double bond at the carbon with more hydrogens, giving the more stable carbocation.
- 2
Water attacks the carbocation (oxonium ion).
- 3
A water molecule removes a proton: the alcohol forms and the acid is regenerated (catalyst).
Practice tasks
Which product forms, which reagent is needed? After each answer you see the explanation.
Which main product forms?
Typical mistakes
Often confused with: Hydroboration–oxidation · Addition of HBr (Markovnikov)
Frequently asked questions
Why is a catalytic amount of acid enough?
The proton is consumed in the first step and returned in the last.
Is the reaction reversible?
Yes, the reverse is dehydration. Lots of water and low temperature favour the alcohol; concentrated acid and heat favour the alkene.