Extreme solvent effects on reaction rate constants at supercritical fluid conditions



The reaction rate constant was adjusted continuously over two orders of magnitude for the unimolecular decomposition of α-chlorobenzyl methyl ether using the supercritical fluid solvent 1, 1 diffluoroethane. Activation volumes were observed as low as −6,000 cm3/mol, which is about an order of magnitude more negative than those reported previously in the literature for a homogeneous reaction. Spectral shift (solvatochromic) data were measured for phenol blue in the same fluid in order to interpret the rate data. A method is presented to predict solvent effects on rate constants at supercritical fluid conditions.