Dicinnamalacetone

Dicinnamalacetone is a conjugated organic compound. It is used as an indicator for the presence of hydrogen halides in solvents,^[1][2] and its preparation is used as an example of the aldol condensation in organic chemistry teaching labs.^[3][4]

Dicinnamalacetone

Names
Systematic IUPAC name (1E,3E,6E,8E)-1,9-Diphenyl-1,3,6,8-nonatetraen-5-one
Other names Dicinnamylideneacetone 1,9-diphenyl-1,3,6,8-nonatetraen-5-one
Identifiers
CAS Number	622-21-9
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL388544
ChemSpider	4527132
EC Number	210-724-0
PubChem CID	5378259
InChI InChI=1S/C21H18O/c22-21(17-9-7-15-19-11-3-1-4-12-19)18-10-8-16-20-13-5-2-6-14-20/h1-18H/b15-7+,16-8+,17-9+,18-10+ Key: RLJALOQFYHCJKG-FVRNMFRHSA-N
SMILES C1=CC=C(C=C1)/C=C/C=C/C(=O)/C=C/C=C/C2=CC=CC=C2
Properties
Chemical formula	C21H18O
Molar mass	286.374 g·mol−1
Appearance	Yellow crystalline solid
Melting point	143 °C (289 °F; 416 K) [1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation

Dicinnamalacetone (specifically the all-trans isomer) may be prepared by the reaction of acetone and trans-cinnamaldehyde catalyzed by a strong base, such as potassium hydroxide. The reaction is typically conducted in a mixture of water and ethanol.^[1][3]

Clock reaction

The preparation of dicinnamalacetone is an example of a clock reaction. Upon the addition of acetone to a solution of trans-cinnamaldehyde and potassium hydroxide in ethanol and water, a precipitate of dicinnamalacetone forms spontaneously after a delay.

The formation of dicinnamalacetone constitutes two separate aldol condensations. In the first, one molar equivalent of trans-cinnamaldehyde and one molar equivalent of acetone condense to form a soluble intermediate compound:

This intermediate compound then condenses with another molar equivalent of trans-cinnamaldehyde to form dicinnamalacetone, which is insoluble in the reaction mixture:

The first condensation is believed to be relatively slow compared to the second, hence the delay between the addition of all of the reactants and the formation of a precipitate.^[3]