Chemistry - STRUCTURAL ISOMERISM Question with Solution | TestHub

Enol content tracks the stability of the enol. (A) cyclohexane-1,2-dione gives a conjugated, intramolecularly H-bonded enol (2-hydroxycyclohex-2-en-1-one) - high content. (D) cyclohexane-1,3-dione also gives a conjugated, H-bonded enol - high content. (C) cyclohex-2-en-1-one gives an ordinary dienol - moderate content. In (B), bicyclo[2.2.1]heptan-7-one, the only alpha carbons are the two bridgeheads; enolisation would place a double bond at a bridgehead of a small bicyclic system, violating Bredt's rule, so its enol content is the minimum (essentially zero).