Free Radical Chlorination of Alkanes in Supercritical Carbon Dioxide:  The Chlorine Atom Cage Effect as a Probe for Enhanced Cage Effects in Supercritical Fluid Solvents

The chlorine atom cage effect was used as a highly sensitive probe for studying the effect of viscosity and the possible role of solvent clusters on cage lifetimes and reactivity for reactions carried out in supercritical fluid solvents. These experiments were conducted in supercritical carbon dioxide (SC-CO 2, 40 °C, at various pressures) with parallel experiments in conventional solvents and in the gas phase. The results of these experiments provide no indication of an enhanced cage effect near the critical point in SC-CO 2 solvent. The magnitude of the cage effect observed in SC-CO 2 at all pressures examined is well within what is anticipated on the basis of extrapolations from conventional solvents.