Q.Peroxide effect (Kharasch effect) can be studied in case of

Anti-Markovnikov Addition (Peroxide Effect)

When HBr adds to an unsymmetrical alkene in the presence of an organic peroxide, the regiochemistry REVERSES relative to ordinary (ionic) Markovnikov addition -- bromine ends up on the LESS-substituted carbon instead. This anti-Markovnikov outcome is called the peroxide effect or Kharasch addition, and it happens because the peroxide switches the mechanism from ionic to FREE-RADICAL.

Mechanism: (1) the peroxide's weak O-O bond homolyses to give radicals that abstract an H from HBr, generating a bromine radical (the actual chain-carrying species, not H+ this time); (2) the bromine radical adds FIRST to the alkene, at whichever carbon gives the MORE STABLE resulting carbon radical (again tertiary > secondary > primary, by the same hyperconjugation logic as carbocations) -- for a terminal alkene like propene, that means Br bonds to the terminal (less substituted) carbon, placing the radical on the more-substituted internal carbon; (3) that carbon radical then abstracts an H from another HBr molecule, completing the addition and regenerating a bromine radical to continue the chain. Since Br adds FIRST (gove …