major product of addition of hbr in 2 methyl propene in presence of peroxide3 / 3

The reaction you're referring to is an example of anti-Markovnikov addition, which occurs in the presence of peroxides. Here's the step-by-step process:

1. The reaction begins with the formation of a bromine radical, due to the homolytic cleavage of the Br-Br bond in the presence of peroxides.

2. This bromine radical then attacks the 2-methylpropene molecule at the least substituted carbon (due to its higher reactivity), forming a secondary carbon radical.

3. Finally, this secondary carbon radical reacts with a molecule of HBr, with the hydrogen attaching to the carbon with the unpaired electron and the bromine attaching to the carbon adjacent to it.

The major product of this reaction is 1-bromo-2-methylpropane.