Kinetics of ligand-substitution in glycerol at high pressures, by a laser temperature-jump method
Abstract
The kinetics of the reactions of the ligand pyridine-2-azo-p-dimethylaniline with CoII, NiII, CuII and ZnII ions in glycerol have been studied, at pressures up to 2760 b over a range of temperatures. Activation enthalpies and volumes are reported for CoII and ZnII. The rate constants for the four cations at 1 b and 20°C are the same within a factor of 4; they are smaller than the value calculated for diffusion control, by a factor of 102 to 103. The activation enthalpies for CoII and ZnII are close to that expected for diffusion control. The activation volume for ZnII is fairly close to the diffusion-controlled value, but that for CoII is smaller. The results are discussed in relation to a model which takes into account diffusion, steric factors and ring closure.