Unique Pressure Effects on the Absolute Kinetics of Triplet Benzophenone Photoreduction in Supercritical CO2

Article abstract of DOI:10.1021/ja00048a016

Laser flash photolysis studies of the hydrogen atom abstraction reaction of triplet benzophenone from 2-propanol and 1,4-cyclohexadiene in supercritical CO2 reveal unusual pressure effects on absolute rate constants.Monitoring reactivity close to the critical temperature (T_c) revealed that bimolecular rate constants increase sharply with a decrease in pressure, approaching the critical point.Kinetic investigations along an isotherm further removed from T_c and predictive calculations on the pressure effect expected in supercritical CO2 indicate that enhanced reactivity is due to local substrate clustering.