Dicinnamalacetone
Chemical compound
From Wikipedia, the free encyclopedia
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]
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| Systematic IUPAC name
(1E,3E,6E,8E)-1,9-Diphenyl-1,3,6,8-nonatetraen-5-one | |
Other names
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| Properties | |
| 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).
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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]