Enhancing the rate of the Diels-Alder reaction using CO(sub 2)+ ethanol and CO(sub 2)+ n-hexane mixed solvents of different phase regions

The reaction rate of the Diels-Alder reaction between N-ethylmaleimide and 9-hydroxymethylanthrance in CO(sub 2) + ethanol and CO(sub 2) + hexane mixed solvents of different compositions were determined by in situ UV/vis spectroscopy at 318.15 K and different pressures. The result states that at the same temperature the reaction can not be conducted in pure supercritical CO(sub 2) in the highly compressible region due to the solubility limitation of 9-hydroxymethylanthrance in supercritical CO(sub 2) at the lower pressures, while the reaction can be carried out in the highly compressible mixed solvents, and reaction rate is effective by pressure.