Identify the major product formed in the following reaction:

Step-by-step solution

The given reaction is the acid-catalyzed condensation (cyclotrimerization) of butan-2-one (ethyl methyl ketone) in the presence of concentrated H ₂ SO ₄ . In acid-catalyzed aldol-type reactions, enolization preferentially occurs at the more substituted -carbon to form the more stable (thermodynamic) enol. For butan-2-one, the enolization occurs at the methylene ( -CH ₂ - ) group rather than the methyl ( -CH ₃ ) group. Three molecules of butan-2-one undergo condensation where the carbonyl carbon of one molecule reac