The Total solution for NCERT class 6-12
Additionof HBr to propene is an ionic electrophilic addition reaction in which theelectrophile, i.e., H+ first adds to give a more stable 2°carbocation. In the 2nd step, the carbocation is rapidly attacked by thenucleophile Br~ ion to give 2-bromopropane.In presence of benzoyl peroxide, the reaction is still electrophilic but theelectrophile here is a Br free radical which is obtained by the action ofbenzoyl peroxide on HBrIn the first step, Br radical adds to propene in such a way so as to generatethe more stable 2° free radical. In the second step, the free radical thusobtained rapidly abstracts a hydrogen atom from HBr to give 1-bromopropane.From the above discussion, it is evident that although both reactions areelectrophilic addition reactions but it is due to different order of additionof H and Br atoms which gives different products.