Addition of HBr (Markovnikov): practice and mechanism
Without peroxide the proton adds first, so that the more stable carbocation forms: Br ends up on the more substituted carbon (Markovnikov).
Example
HBr adds electrophilically: the proton goes to the carbon with more hydrogens, forming the more stable (more substituted) carbocation, where bromide then binds (Markovnikov's rule).
Mechanism step by step
- 1
The π electrons of the double bond attack the proton of HBr.
- 2
H goes to the carbon with more hydrogens, giving the more stable, more substituted carbocation.
- 3
Bromide attacks the carbocation: Br sits on the more substituted carbon.
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: Radical addition of HBr (anti-Markovnikov) · Addition of bromine
Frequently asked questions
A memory aid for Markovnikov?
"The rich get richer": H goes to the carbon that already has more hydrogens.
Does it apply to HCl and HI too?
Yes, the regioselectivity always follows the more stable carbocation. The peroxide effect (anti-Markovnikov) only occurs with HBr.