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React with acid/base open peroxide ring

Discussion in 'DAT Discussions' started by vvvv, Jun 5, 2008.

  1. vvvv

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    destroyer OC # 24 said that when in acid, it will attack the more substituted carbon. When in base, attack the least substituted carbon. This is very clear to me.
    However, in the McMurry page 651 said, when in acid, if only primary and secondary, it will attack the less substituted by SN2. but when tertary present, it attack to high substituted by SN1.

    what am i missing here?

    please.
     
  2. Mstoothlady2012

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    opening of an epoxide is a substitution reaction so you know you are working with SN1 or SN2. It depends on the ring whether it is going to go under SN1 or SN2. If you have a tertiary carbon then no doubt it will favor SN1...because SN2 doesn't even stand a chance. Where else if neither carbon is tertiary then it is hard for the reaction to follow SN1 since the carbocation will not be very stable since the carbon atoms are either primary or secondary. So the reaciton would rather under go SN2...which carbon atom is more favored by SN2....primary or secondary? I think you know that very well. Hope this helps! :thumbup:
     
  3. vvvv

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    If you agree with me that when primary and secondary present in acid. it will substituted the less hindered side carbon. so the answer for #24 in destroyer is not correct. because they attack to secondary and explain that acid will attack to high sub....
     
  4. Mstoothlady2012

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    oh I am sorry I didnt look at destroyer's question. Well here the reaction has to undergo SN1 because isn't ethanol a poor nucleophile?
     
  5. vvvv

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    got it, i didnt pay attention to ethanol, because i thought if in acid condition, then do not need to look at good or poor nucleophile
     
  6. vvvv

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    I have an extra question here. ethanol is poor nucleophile but in solution it become CH3CH2O- then this is a strong nucleophile. we dont consider this ion instead of ethanol by itself. because ion is actualy attack, not ethanol.
     
  7. Mstoothlady2012

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    no it doesn't loose the proton, the reaction is taking place under acidic condition. If anything it will gain a proton.
     
  8. vvvv

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    So for example HBr in acid condition, do they lose their proton? sorry for too many questions
     
  9. Mstoothlady2012

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    I forgot about oxygen on the ring. you are right it has to loose proton because oxygen will grab it. I think you should call Dr. Romano and ask him about this. I think I faced this problem last year too when I was studying....but I don't remember what he had told me. If you call him please let me know what he says..i would love to get this cleared up as well. Sorry couldn't help you!
     
  10. vvvv

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    do you have a number that I can call?
     

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