Home > Organic Chemistry > Radical Halogenation of Alkenes (Antimarkovnikov)

Why can an anti-markovnikov radical addition of haloalkane only happen in presence of hydrogen peroxide?

Answer 1

In a "normal" Markovnikov attrition of #"HBr"# to an alkene, the #"H"# adds to the carbon with more hydrogen atoms in order to form the more stable carbocation.

In the peroxide-catalyzed addition, the bromine radical adds to the carbon with more hydrogen atoms in order to form the more stable radical.

That means that the #"H"# must go on the carbon with fewer #"H"# atoms.

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Answer 2

Ryan Andrews

The presence of hydrogen peroxide facilitates the formation of a radical initiator, which generates radicals. These radicals undergo anti-Markovnikov addition with haloalkanes, resulting in the anti-Markovnikov product.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.