ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 29, Number 5
JKCSEZ 29(5)
October 20, 1985 

The rates for the aquation of cis-[Co(en)(NH3)2Cl2]Cl in acetone-water mixtures have been measured at various pressures and temperatures by the electric conductivity method. The rate constant measured at 25℃ in pure water solvent is 3.47 × 10-4/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∼+8.2cm3/mole. The rate constants in aqueous acetone solution are analyzed with the solvent compositions. Plots of log kobs vs. Grunwald-Winstein Y values show that log kobs 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 (Id).