Photo-Fries Rearrangement of Naphthyl Acetate in Supercritical Carbon Dioxide: Chemical Evidence for Solvent—Solute Clustering

摘要

The critical temperature (T_c) of a substance defines the last point on the liquid-vapor curve of its phase diagram; below this temperature the gas and liquid phases can exist in equilibrium, and compression of the gas ultimately results in liquefaction. Above T_C, the fluid is said to be in its supercritical phase, and compression results in increased density but does not lead to phase separation. Sufficiently dense supercritical fluids have the ability to dissolve relatively nonvolatile solutes, and this has led to their development as alternatives to organic solvents for extraction in chemical and biotechnological processes and as mobile phases for chromatography. For the chemist, supercritical fluids offer exciting possiblities because variations in the density, viscosity, diffusivity, and dielectric properties can be induced simply by varying the pressure or the temperature; these variations are particularly dramatic in the region just above the critical point and potentially can alter the rate or course of chemical processes.