Pressure Effects on the Aquation of $cis-[Co(en)(NH_3)_2Cl_2]Cl$ in Acetone-Water Mixtures

TLDR: In this paper, the rates for the aquation of in acetone-water mixtures have been measured at various pressures and temperatures by the electric conductivity method and the activation volumes and other activation parameters are calculated from these rate constants.

Abstract: The rates for the aquation of in acetone-water mixtures have been measured at various pressures and temperatures by the electric conductivity method. The rate constant measured at 25C in pure water solvent is 3.47 /sec. Rate constants are increased with increasing temperature, and decreased with increasing pressure and mole fraction of acetone. Activation volumes and other activation parameters are calculated from these rate constants. The activation volumes are all positive and lie in the limited range +2.82~+/mole. The rate constants in aqueous acetone solution are analyzed with the solvent compositions. Plots of log vs. Grunwald-Winstein Y values show that log varies linearly and the gradients are about 0.25. The applications of a free energy cycle relating the process initial state transition state in water to that in acetone-water mixture show that the changes in solvation of the transition state have a dominant effect on the rate. From these results the aquation of this complex would be discussed in terms of dissociative mechanism ().