Free-Radical Addition of HBr In the presence of peroxides,HBr adds to an alkene to form the "anti-Markovnikov'product. Peroxides produce free radicals. Only HBr has the right bond energy. The HCI bond is too strong,so it will add according to Markovnikov's rule,even in the presence of peroxide. The HI bond tends to break heterolytically to form ions,it too will add according to Markovnikov's rule. Chapter 8 9 Chapter 8 9 Free-Radical Addition of HBr • In the presence of peroxides, HBr adds to an alkene to form the “anti-Markovnikov” product. • Peroxides produce free radicals. • Only HBr has the right bond energy. • The HCl bond is too strong, so it will add according to Markovnikov’s rule, even in the presence of peroxide. • The HI bond tends to break heterolytically to form ions, it too will add according to Markovnikov’s rule