Question

between acetone and benzaldehyde which one has alpha carbon and how many aldol pairs it can make​

Answer 1

You will do a double mixed-aldol condensation reaction between acetone and benzaldehyde. Acetone has α-hydrogens (on both sides) and thus can be deprotonated to give a nucleophilic enolate anion. The aldehyde carbonyl is much more electrophilic than that of a ketone, and therefore reacts rapidly with the enolate.