Aldol condensation reaction between which of the following pair of compounds followed by dehydration gives 3-phenylprop-2-en-1-al?

The target product is 3-phenylprop-2-en-1-al, which has the structure $C_{6}H_{5}-CH=CH-CHO$.

This compound is an $\alpha,\beta$-unsaturated aldehyde. Aldol condensation between an aldehyde containing an $\alpha$-hydrogen and another carbonyl compound followed by dehydration typically yields such products.

The structure $C_{6}H_{5}-CH=CH-CHO$ can be retrosynthetically broken down at the double bond into benzaldehyde ($C_{6}H_{5}CHO$) and acetaldehyde ($CH_{3}CHO$).

The reaction proceeds as follows: Benzaldehyde ($C_{6}H_{5}CHO$) reacts with acetaldehyde ($CH_{3}CHO$) in the presence of a dilute base. Acetaldehyde provides the $\alpha$-hydrogen to form an enolate, which attacks the carbonyl carbon of benzaldehyde to form 3-hydroxy-3-phenylpropanal. Subsequent dehydration of this aldol product yields 3-phenylprop-2-en-1-al (cinnamaldehyde).

Answer: Benzaldehyde and Acetaldehyde