Identify the structure of the major product Y formed in the following base-catalyzed cyclization reaction.

Step-by-step solution

The given reactant is 4-acetyl-4-methylcyclohexan-1-one. In the presence of a mild base like Na ₂ CO ₃ , an intramolecular aldol condensation takes place. The base abstracts an acidic -hydrogen to form an enolate. The most favorable enolate for cyclization is formed by the deprotonation of the methyl group of the acetyl moiety, yielding a - C (= O ) CH ₂^- carbanion. This nucleophilic carbanion undergoes an intramolecular attack on the electrophilic carbonyl carbon at C-1 of the cyclohexane ring. This attack forms