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

[utsav55]

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

99% or 1%? Also give reason.

Thanks

 

[Borek]

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.

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methods

 

[utsav55]

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%.

 

[sjb-2812]

What is the definition of aromatic, in this case?

 

[chemisttree]

I was going to say 99+% because in the enol form, you have the formation of the aromatic structure.

 

[Borek]

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

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methods

 

[chemisttree]

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...