Free interactive chemistry · SIM-ORG-RAD-002

Peroxide effect

The peroxide effect: with peroxide, HBr adds to an alkene the “wrong” way (anti-Markovnikov).

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How to use this simulation

Play the mechanism or step through it.
Watch the Br radical add first, making the more stable carbon radical.
Compare with the ionic addition in the electrophilic-addition mechanism.

What to notice

Only HBr shows this effect — not HCl or HI.
Br ends up on the carbon with more hydrogens.

Try this

Predict both products of propene + HBr, with and without peroxide.

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