Free Radical addition to Alkenes It is possible to obtain anti-Markovnikov products when HBr is added to alkenes in the presence of free radical initiators. The free radical initiators change the mechanism of addition from electrophilic addition to free radical addition. This change of mechanism gives rise to the opposite regiochemistry Initiation: 6-R R-+·-R R-0+H- R-O一H+:Br The oxygen-oxygen bond is weak,and is easily homolytically cleaved to generate two alkoxy radicals,which in turn abstract hydrogen to generate bromine radicals. Cho8 Reacns of Alkenes (landscape) Page 5Ch08 Reacns of Alkenes (landscape) Page 5 Free Radical addition to Alkenes It is possible to obtain anti-Markovnikov products when HBr is added to alkenes in the presence of free radical initiators. The free radical initiators change the mechanism of addition from electrophilic addition to free radical addition. This change of mechanism gives rise to the opposite regiochemistry. Initiation: The oxygen-oxygen bond is weak, and is easily homolytically cleaved to generate two alkoxy radicals, which in turn abstract hydrogen to generate bromine radicals