24. Enolate Chemistry: Reactions at the Alpha-Carbon

Explain why 92% of 2,4-pentanedione exists as the enol tautomer in hexane but only 15% of this compound exists as the enol tautomer in water.

Pentane-2,4-dione (acetylacetone) exists as a tautomeric mixture of 8% keto and 92% enol forms. Draw the stable enol tautomer, and explain its unusual stability.

Draw the enol tautomers for each of the following compounds. For compounds that have more than one enol tautomer, indicate the one that is more stable.

d.

e.

Rank these compounds in order of increasing acid strength.

Rank these compounds in order of increasing enol content. In each case, draw the most stable enol.