The formation of n -propyl bromide in presence of peroxide can be explained as follow: Step 1 : Peroxide undergoes fission to give free radicals. R−O−O−R⟶2R−
●
O
Step 2 : HBr combines with free radical to form bromine free radical. R−
●
O
+HBr⟶R−OH+
●
B
r Step 3 :
●
B
r attacks the double bond of the alkene to form a more stable free radical.