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What will be the % of Enol form of this compound?

  1. Nov 16, 2009 #1
    What will be the % of Enol form of this compound?

    99% or 1%? Also give reason.

    a1pdg9.png


    Thanks
     
  2. jcsd
  3. Nov 16, 2009 #2

    Borek

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    Try to draw enol form(s).

    If it is a homework question (and it surely looks like one), you have asked in the wrong forum.

    --
    methods
     
  4. Nov 16, 2009 #3
    It is not homework, its a doubt.

    I think, it is 1% as Keto form is Aromatic and hence more stable, but the answer is 99%.
     
  5. Nov 16, 2009 #4
    What is the definition of aromatic, in this case?
     
  6. Nov 17, 2009 #5

    chemisttree

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    I was going to say 99+% because in the enol form, you have the formation of the aromatic structure.
     
  7. Nov 17, 2009 #6

    Borek

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    That's why I asked to draw enolic form, it should be obvious :smile:

    --
    methods
     
  8. Nov 17, 2009 #7

    chemisttree

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    When calculating the percent of a certain species in solution obtained in a completely reversible reaction (like keto-enol tautomerism) it is useful to remember the relationship between the Gibbs free energy of the process and chemical equilibrium.

    Namely

    DeltaG = -RT ln(K)

    This equation shows us that small differences in energy can have profound changes in percent composition. For stereoisomers (gauche- and anti-, for example) of substituted cyclohexanes, free energy differences of only 2kcal/mol results in >95% of the more stable isomer. A difference of only 4kcal/mol results in >99%.

    Aromatic stabilization energies for benzene are on the order of 20 to 40 kcal/mol...
     
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