The major product of a cross-aldol condensation between compound A and compound B is 4-phenylbut-3-en-2-one. Compound A gives a positive Tollens' test but B does not. When A is treated with concentrated NaOH , it undergoes a disproportionation reaction to give products C and D. The identities of compound B, and products C and D are respectively :

Step-by-step solution

The cross-aldol product is 4-phenylbut-3-en-2-one ( C ₆ H ₅- CH = CH - CO - CH ₃ ). Performing a retro-aldol cleavage across the double bond yields benzaldehyde ( C ₆ H ₅ CHO ) and acetone ( CH ₃ COCH ₃ ). Since compound A gives a positive Tollens' test, A is benzaldehyde and B is acetone. When benzaldehyde (A) is treated with concentrated NaOH , it lacks -hydrogens and undergoes the Cannizzaro reaction. This disproportionation yields benzyl alcohol (compound C) and sodium benzoate (compound D). Answer: Acetone; Be