Question

bromination of propylbenzene gives 1-bromopropylbenzene instead of 2-bromopropylbenzene or 3-bromopropylbenzene upon reaction with N-bromosuccinimide in precence of benzoyl peroxide as a radical initiator

Answer 1

Are you asking why? If you are the benzyl radical (Ph-CH.CH2CH3)is the more stable of the three possible.