Allylic Bromination of Isobutene

Background Colour:


Removal of an alkene H gives a carbon-centred radical localized on the sp2 atom but the removal of an H from a methyl group gives a much more stable delocalized allylic radical.

The allylic radical collects a bromine atom from a bromine molecule and produces a new bromine radical that can start a new series of reactions. Like the addition of HBr ,the reaction is a radical chain reaction, and only a small amount of Br2 needs to break down to Br• to get the reaction going.