A Unique Feature of Ionic Diffusion-Controlled Reactions in Supercritical Fluid

Abstract

Density dependence of the rate constants of diffusion-controlled ionic recombination reactions in supercritical (SC) fluoroform was investigated to explore the effect of the local density enhancement on diffusion-controlled reactions. For the ionic recombination, the effect was clearly detected as strong retardation of reaction rate near the critical density. On the other hand, for the radical self-termination, the effect was not detected. This difference must be due to the strong solute-solvent interaction between ionic species and solvent molecules. The local density around the charged molecules should be drastically enhanced by Coulomb interactions.