Photodimerization of isophorone in supercritical trifluoromethane and carbon dioxide

An examination of the regio- and stereoselectivity for the photodimerization of isophorone in both supercritical CHF{sub 3} and CO{sub 2} as a function of pressure is presented. This selectivity is discussed in terms of solvent polarity and differential solvent reorganization. The stereoselectivity is influenced mostly by solvent reorganization, and the regioselectivity is influenced by both solvent polarity and solvent reorganization. Differential solvent reorganization is shown to exert the dominant effect on the selectivity, and the viability of a supercritical medium as a mechanistic probe is thereby demonstrated.