Which of the following compounds possess more than one percent enol content?

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I understood that stability of enols are dependent on the hydrogen bonding in the compounds. But here, what is the significance of more than one percent enol content?

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    $\begingroup$ I would like to express my disagreement with the assertion that the stability of enols would mainly be dependent on inter- and intra- molecular hydrogen bonding. $\endgroup$
    – user79161
    Mar 26 at 9:15
  • $\begingroup$ @user79161 I mean that h-bonding is one of the factor that could be used for determining the stability of Enols. It need not be the primary factor. $\endgroup$ Mar 26 at 9:53
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    $\begingroup$ Especially because of the nice representations of the formulae (for easier reading, consider to rotate labels, though [entry i]), a more useful question were the comparison of the entries by line to justify which ones are more likely to enolize, than others -- for example in the line of a to d. For some, $\log{}K$ may depend on the molecule's structure as well as (if there is) the solvent molecules. Or -- guessing -- are you literally looking for a tautomer database example? $\endgroup$
    – Buttonwood
    Mar 26 at 9:57
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    $\begingroup$ chemistry.stackexchange.com/questions/18904/… This might help you;@Ron's answer was very extensive. Note that, as Buttonwood pointed out, a fruitful exercise would be to compare likelihood of enolization. To compare the respective percentages would need you to carry out an experiment and interpret that data. $\endgroup$
    – C_Lycoris
    Mar 26 at 12:48

All the compounds that have a relation $\alpha-\beta$ between the carbonyl groups. The hydrogen between two $\ce{CO}$ is very acid because two electrowithdrawing remove electron density from the $\ce{C-O}$ bond. Therefore for this kind of compound the most stable for is the enol. In Organic Chemistry this is very useful in creating new carbon-carbon bonds in mild conditions like in aldoholic reactions, Michael reactions and so on. See the very good book of Marc Loudon, Organic Chemistry.


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