[Fischer]

Hi!
I need some help with the mechanism of free radical addition of bromotrichlorometane to beta/pseudo-pinene catalysed by benzoyl peroxide. I know the cyclobutane ring is supposed to split open, and how benzoyl peroxide undergoes a homolytic cleavage generating 2 radicals. But from there I just can't figure it out.  

I have also guessed that somewhere along the way a trichloromethyl radical should be generated.

[plu]

You are on the right track.  Here's a hint: The first step is the production of the trichloromethyl radical, which attacks at C1, breaking the double bond.

[Fischer]

Thanks plu!
I've understood the mechanism from the trichloromethyl radical  part. What I don't understand is how this is formed. Since benzoyl peroxide is prone to form radicals, and it's used as the catalyst it must be involved. Is it as simple as one of those radicals formed snatch of a bromine from bromotrichloromethane? Somehow this seems like the only way if it isn't something totally unrelated that just happens to end up with a trichloromethyl radical that can attack that carbon. On the other hand it doesn't seem really likely to have a oxygen bonded to a carbon. Anybody care to shed a light? Thanks!