An unknown ketone A and an unknown aldehyde B undergo a cross-aldol condensation in the presence of dilute base to form a major product C. When C is subjected to reductive ozonolysis, it yields an equimolar mixture of benzaldehyde and 2-oxopropanal. The identities of the starting materials A and B are respectively:

Step-by-step solution

Product C on reductive ozonolysis gives benzaldehyde ( PhCHO ) and 2-oxopropanal ( CH₃COCHO ). Reconstructing the alkene C by joining the carbonyl carbons of the fragments with a double bond gives Ph-CH=CH-CO-CH₃ (benzylideneacetone). Since C is formed by a cross-aldol condensation between a ketone and an aldehyde, we perform a retro-aldol analysis on C. Cleavage of the C=C bond assigns the -carbon to the electrophile (aldehyde) and the -carbon to the nucleophile (ketone). The -carbon fragment is Ph-CH , which corr