Benzylideneacetone

Benzylideneacetone is the organic compound described by the formula C6H5CH=CHC(O)CH3. Although both cis and trans isomers are possible for the &alpha;,&beta;-unsaturated ketone, only the trans isomer is observed. Its original preparation demonstrated the scope of condensation reactions to construct new, complex organic compounds.

Preparation
Benzylideneacetone can be efficiently prepared by the NaOH-induced condensation of the readily available reagents acetone and benzaldehyde:
 * CH3C(O)CH3 +  C6H5CHO  &rarr;  C6H5CH=CHC(O)CH3  +  H2O

Reactions
The compound undergoes the reactions expected for its collection of functional groups: e.g., the double bond adds bromine, the heterodiene adds electron-rich alkenes in Diels-Alder reactions to give dihydropyrans, the methyl group undergoes further condensation with benzaldehyde to give dibenzylideneacetone, and the carbonyl forms hydrazones. Treatment of benzylideneacetone with the Grignard reagent methyl magnesium bromide followed by acid-induced dehydration gives 1-phenyl-1,3-butadiene. It reacts with Fe2(CO)9 to give (benzylideneacetone)Fe(CO)3, a reagent for transferring the Fe(CO)3 unit to other organic molecules.

Safety
Benzylideneacetone is a skin irritant.