another orgo question

[pistolpete007]

if u have benzylethane and react it with HBr/ROOR.....


do u get RCH(Br)CH3.....R=benzenegroup

or do u get RCH2CH2Br

the reason why i am confused is because if u have benzylethane and react it with Br2,hv or NBS, ROOR, heat....u get RCH(Br)CH3

HOWEVER if u have methylcyclopentane and react it w/ Br2/hv you get 1-bromo-1-methyl cyclopentane.....however if u react it with HBr/ROOR u get RCH2Br *R=cyclopentane*......

so thats why im wondering if u were to add HBr/ROOR to benzylethane you would get RCH2CH2Br R=benzenegroup.........

and just for the hell of it tell me if this is right as well....methylcyclopentane ---NBS, ROOR, heat--->1-bromo-1-methyl cyclopentane (same as Br2/hv)

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[doc3232]

I am gonna have to say no reaction.
ROOR with HBr requires an electrophile (double bond). Only way for that to work.
Through radical, ROOR initiates and 1 electron comes from the double bond and the other from the Br (which lost one of its 8 electrons during radicalization with ROOR). Then a Hydrogen which has 1 electron on it bonds to the other electron from the double bond.

basically, you need a double bond for this to happen.
Actually I can't think of a situation when a double bond is not needed (so the radicals can work).
Hope this helps

 

[pistolpete007]

thanks man....is this right tho methylcyclopentane ---NBS, ROOR, heat--->1-bromo-1-methyl cyclopentane (same as Br2/hv)

 

[doc3232]

Yes, but I don't think you need heat. At least not in my book, but either way that isn't important.