[BetaAmyloid]

This is in response to a thread that dealt with the addition of HBr to vinyl chloride and the formation of either 1,1-dibromoethane or 1,2-dibromoethane.

This is also in response to a paper that Dan posted that I read here: http://pubs.acs.org/doi/pdf/10.1021/ja01333a048

I understand experimentally what the results are, but how does the peroxide effect actually affect this particular reaction? Affect reactions in general?

I know this paper is from 1933, perhaps there is a new term for the peroxide effect now-a-days.

As a side note...I'm still an undergrad, but I didn't know peroxide resided in many compounds (if that is right)? How does peroxide form in materials?

That may be a large question, so if there is not a specific answer, I always enjoy reading what has already been published out there.

Thanks for the responses.

[discodermolide]

Have a read here.
http://www.chemguide.co.uk/mechanisms/freerad/alkenehbr.html

[BetaAmyloid]

Have a read here.
http://www.chemguide.co.uk/mechanisms/freerad/alkenehbr.html

Cool, thanks.

So HBr happens to be just right for the peroxide effect.

A question to the mechanism: Why do these peroxides happen to become free radicals, why don't they want to stay as peroxides? Is the bond between oxygens so unstable that it would rather form a radical to accept a proton?

Also, again -- why are these peroxides present in something such as vinyl chloride and why do they increase in concentration over time? I guess I don't understand the formation of radicals from the environment. I found autoxidation, nevermind. But still the free radical question remains above.

Thanks for the read and response.

[discodermolide]

Presumably these peroxide radicals form because the O-O bond strength is low, around 50 Kcal/mol, and the action of UV causes the bond to break. This is why some polymers degrade after long exposure to light.

[BetaAmyloid]

Ah, okay, makes sense.

Thanks for the insight!