Question

Define (reaction only) the base catalyzed cross-aldol condensation reaction between excess benzaldehyde and propanaldehyde (No mechanism needed)!

Answer 1

Addition of α-carbon of an enolizable aldehyde or ketone to the carbonyl group of another aldehyde or ketone to form β-hydroxy carbonyl compound followed by loss of a water molecule to form α, β-unsaturated carbonyl compound is called aldol condensation reaction.

In case two different types of carbonyl compounds are used, the reaction will be called crossed aldol condensation reaction.

Benzaldehyde lacks enolizable proton on α-carbon, while propanaldehyde has such proton and can form enolate ion when treated with base.

In base catalyzed crossed aldol condensation reaction between excess of benzaldehyde and propanaldehyde, α-carbon of the enolate of propanaldehyde adds to the carbonyl group of benzaldehyde to give β-hydroxy carbonyl compound. This further due to base catalysis, loses a water molecule to form α, β-unsaturated carbonyl compound, 2-methyl-3-phenylacrylaldehyde.

он о base base benzaldehyde propanaldehyde 2-methyl-3-phenylacrylaldehyde