[DoctorB2B]

So for my first post, I have a problem with a mechanism ...

1. The problem statement, all variables and given/known data
I am given isobutane as my starting material, Br₂ and benzoyl peroxide as my radical initiators. My final product is the isobutane with Br attached instead of H.

I have to design the mechanism. I have tried what seems like an endless combination of mechanism attempts, and can't seem to get it. I do not have to include the termination steps, only the initiation and propagation steps.

2. The attempt at a solution
-I homolyzed the Br atom and the benzoyl peroxide at the same time in step one.
-In step two, I took one of the benzoyl peroxide radicals and attempted to remove the H from isobutane creating a radical off the alkyl group.
-In step three, I homolyzed another Br₂ molecule added it onto the isobutane radical.
-In step four, I didn't know what to do.

Evidently I have my steps all screwed up. I don't know when I'm supposed to homolyze the peroxide and then what I'm supposed to do with it. Any help would be greatly appreciated.

[plankk]

How can you homolyzed the Br atom?  In the first step (the initiation step) homolyzed only beznoyl peroxide. The next two steps which you propsed are correct. Think what products come into being in the third step? Which of them can propagate the reaction?

Good luck!