Our website is evolving and our goal is to create a great user experience for our readers and authors. You will see regular enhancements to our site in the coming months.
Please visit our news site for further information.
We examined two crossed aldol condensations in pure liquid water at temperatures of 250, 300, and 350 °C. We synthesized benzalacetone from benzaldehyde and acetone, and chalcone from benzaldehyde and acetophenone. We provide evidence that these reactions are acid and base catalyzed in high-temperature water. Benzalacetone was always the major reaction product in its experiments and chalcone was almost always the major product in its synthesis experiments. At 350 °C and long reaction times (5 and 8 hours) the chalcone yields were surpassed by those of 3-phenylpropiophenone. The maximum molar yield from the benzalacetone synthesis was 24% at 250 °C and 5 hours, and the maximum yield of chalcone was 21% at 250 °C and 15 hours. At higher temperatures, the yield of the unsaturated ketone products was lower due to formation of degradation products such as benzoic acid, benzyl alcohol, benzylacetone, acetophenone, E-stilbene, propiophenone and diphenylethane. A reaction network with reversible formation of the unsaturated ketone, its degradation, and a path for benzaldehyde disproportion provided the basis for a quantitative reaction model. These results provide another illustration of the ability of HTW to facilitate acid- and base-catalyzed reactions without any added acid or base.
Fetching data from CrossRef. This may take some time to load.