Question

In THE PREPARATION OF DIBENZYLIDENEACETONE from Benzaldehyde and acetone using NaOH as a catalyst

show a ‘curly arrow’ mechanism for the conversion of acetone to dibenzylideneacetone, and What would be the product if a 1:1 mixture of benzaldehyde and acetone were used in this reaction?

Answer 1

Reaction of Benzaldehyde and acetone is an example of aldol condensation reaction. H20 acetone enolate benzaldehyde B-hydroxy aldehyde (aldo) 21 meio - Golpo do thogalo heat -H20 2nd molecule of benzaldehyde Na 0 H20 heat -H20 dibenzylideneacetone In the first step, acetone on reaction with sodium hydroxide give sodium enolate which on reaction with benzaldehyde followed by protonation give addition product B-hydroxy aldehyde. This product on heating undergo dehydration to give alkene product. Reaction of alkene on second side with NaOH followed by reaction of enolate with 2nd molecule of benzaldehyde give second addition product, which on protonation followed by dehydration give dibenzylideneacetone as shown above. if one uses a 1:1 mixture of benzaldehyde and acetone in this reaction, the reaction stops at the first alkene product statge as there is no other reactant available for the formation of second side product