Acetophenone ($C_6H_5COCH_3$) contains $\alpha$-hydrogens. In the presence of a strong base like sodium ethoxide ($C_2H_5ONa$), it undergoes self-condensation (Aldol condensation).

1. Enolate Formation: The base abstracts an $\alpha$-proton from one molecule of acetophenone to form an enolate ion.
2. Nucleophilic Attack: The enolate attacks the carbonyl carbon of another acetophenone molecule.
3. Dehydration: The initial aldol product (eta-hydroxy ketone) loses a water molecule upon heating or in the stable basic medium to form an $\alpha,\beta$-unsaturated ketone.

The final product is 1,3-Diphenyl-2-buten-1-one (common name: Dypnone).

Reaction: $2 C_6H_5COCH_3 \xrightarrow{C_2H_5ONa} C_6H_5C(CH_3)=CHCOC_6H_5 + H_2O$