Addition of HBr to propene yields 2-bromo propane, while in presence of benzoyl peroxide the same reaction yields 1-bromopropane. Explain and give mechanism



Addition to HBr to propene (unsymmetrical alkene) follows Markovnikov Rule according to which the negative part of the addendum gets attached to that C atom which possesses lesser number of hydrogen atoms. Thus according to this rule 2-Bromopropane is the expected product. In actual practice, it is found as the major product