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Phenol Acidity ?

Discussion in 'DAT Discussions' started by busupshot83, Apr 30, 2007.

  1. busupshot83

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

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    Mar 22, 2003
    Texas
    Is the following true?

    Halogens are deactivating, but direct ortho/para.
    Deactivating groups increase phenol acidity.
    Therefore, halogens will increase phenol acidity.

    If so, do nitro groups cause a greater increase in phenol acidity than halogens?
     
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  3. poc91nc

    poc91nc Banned Banned 7+ Year Member

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    Yup halogens are deactivating and direct ORTHO PARA...same goes for -NO

    Deactivating groups will increase acidity..especially at ortho-para. para-nitrophenol more acidic than meta-nitrophenol

    Halogens will increase acidity...but not as good as nitro.
     
  4. busupshot83

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

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    Awesome, thanks Poc.
     
  5. poc91nc

    poc91nc Banned Banned 7+ Year Member

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    I mean halogens direct ortho para but are deactivating same with -NO
     
  6. busupshot83

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

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    K, I was just about to ask you about that.
     
  7. poc91nc

    poc91nc Banned Banned 7+ Year Member

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    There is one other not commonly asked deactivator that is ortho/para directing...in addition to halogens and -NO...but I can't think of it...just something to keep in mind.
     
  8. busupshot83

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

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    Yeah, good looking out: NO is one of them. I can't think of the other neither. Thanks again, you have been a huge help. I'm going to study again, pce.
     
  9. DailyDrivenTJ

    DailyDrivenTJ 2+ Year Member

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    Mar 20, 2007
    Phenol's acidity is increased when EWG is present on the ring. This is because once the proton/hydrogen from the oxygen is removed, the conjugate base is stablized by the electron withdrawing group on the ring such as halogen. This is what makes the phenol acidic. EWG on O/P position will yield more acidic product via resonance stablization compared EWG on the meta position via induction.
     
  10. lor

    lor 2+ Year Member

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    Nov 27, 2006
    in aromatic molecules,
    the acidity increase by adding an electron with-drawing group to the ring. it could be NO2 or Br etc.
    the basisity of the ring on the other hand increase with the electron donating groups such as NH2
    what if you have to groups attached to the aromatic ring, let's say NO2 and NH2 and you are asked to add another one to the ring...make sure you go by the configuration of electron donating/activating group in this case NH2. so you need to think ortho and para in this case
    KNOW pages 321, 324 and 326 of the Kaplan blue book as well, you don't regret it:D
    best of luck
     
  11. theedaddy77

    theedaddy77 2+ Year Member

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    May 9, 2008
    no2 is electron withdrawing and M derecting..... not ortho para. While halogens are elctron withdrawing but are Ortho para due to increase resonance.
     
  12. ucla2134

    ucla2134 7+ Year Member

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    Nov 19, 2006
    What is EWG?
    Thanks
     
  13. TeamGuo

    TeamGuo 2+ Year Member

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    Apr 1, 2008
    electron withdrawing. Ex. NO2 :thumbup:
     
  14. ddsjc2014

    ddsjc2014 7+ Year Member

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    Oct 22, 2007
    yep...NO2 is M directing, EWG. increase acidity than halogens.
     
  15. ucla2134

    ucla2134 7+ Year Member

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    Nov 19, 2006
    If NO2 is M directing EWG, the why in the kaplan book says that methyl group directs substitution products for M is only for 3%, but ortho and para it is 63% and 34% respectively??
    Anyone know this?
    Thanks
     

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