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Destroyer - Organic # 16

Discussion in 'DAT Discussions' started by busupshot83, Apr 11, 2007.

  1. busupshot83

    busupshot83 S.D.N. Vet 7+ Year Member

    Mar 22, 2003
    I understand that stability of radicals is as follows:

    primary < secondary < tertiary < allylic

    What I don't understand in this problem is how answer (E) is more stable than answer (B). The way I see it...

    (E) is tertiary allyl
    (B) is tertiary allyl

    However, the solutions say that (B) is tertiary vinylic. What is the difference between allylic and vinylic?
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  3. jfitzpat

    jfitzpat 10+ Year Member

    Nov 27, 2005
    I am pretty sure it is because choice E is resonance stabilized by the pi bond (allylic). Since there is no way to configure a resonance stabilization of B, it would be less stable than answer E.
  4. BodybldgDoc

    BodybldgDoc Guest

    Jan 13, 2007
    In your closet
    a vinyl group is R-CH=CH2 whereas an allyl group is CH2=CH-CH2-R and as you can see an allyl group can delocalize its Pi electrons which makes it more stable as opposed to a vinyl group which is why the answer would be E
  5. DentalKitty

    DentalKitty 5+ Year Member

    Mar 12, 2007
    Vinylic is when the + charge is on a C that has the double bond. Allylic is when the + charge is on a C next to a C with a double bond. Like mentioned above, when you have allylic it is similar to conjugated double bonds where the pi electrons can delocalize and form resonance structures which stabilizes the cation. With vinylic, the charge cannot be delocalized so it is less stable. Not having the ability to delocalize has to do with the orientation of the orbitals and them not being in the same plane. Hope this helps!

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