Question

Treatment of the minor product formed in the intramolecular aldol cyclization of 2,5-heptanedione (Problems 23-51 and 23-52) with aqueous NaOH converts it into the major product. Propose a mechanism to account for this base-catalyzed isomerization.

Short answer

The mechanism for the minor product formed in the intramolecular aldol cyclization of 2,5-heptanedione is reversible aldol condensation.

Step-by-step solution

Mechanism

In this reaction mechanism all steps are reversible aldol condensation hence stable compounds are formed at equilibrium.

The reaction starts with the addition of the -OH group and ends with aldol condensation and dehydration.

The mechanism to convert the minor product into major: