Acetophenone when reacted with a base, C ₂ H ₅ ONa , yields a stable compound which has the structure

Step-by-step solution

The reaction is an aldol condensation. C₂H₅ONa (strong base) removes an -hydrogen from acetophenone ( Ph-CO-CH₃ ) to form an enolate ion. The enolate attacks the carbonyl carbon of a second acetophenone molecule, forming a -hydroxy ketone (aldol addition product). Since a stable compound is specified, the -hydroxy ketone undergoes dehydration to form an , -unsaturated ketone. The resulting C=C extends conjugation with both the carbonyl group and the adjacent phenyl ring, providing significant resonance stabilisatio