Publication Date

8-1978

Advisor(s) - Committee Chair

Robert Farina, Norman Holy, Curtis Wilkins

Degree Program

Department of Chemistry

Degree Type

Master of Science

Abstract

The rate of reduction of [Co(dipy)3]3+ by [Co(tripy)2]2+ has been examined in six nonaqueous solvents and water. The kinetic results in these solvents were compared with those obtained in nine other solvents where the same reaction was investigated. Activation parameters were obtained over a temperature range of 5° to 50°C with the ionic strength at 0.0027 or 0.0046 M. The slowest rate of electron transfer was found in acetonitrile while the fastest occurred in acetophenone, the solvent of lowest dielectric constant. A linear correlation between ln k and the reciprocal dielectric constant of the solvent was obtained for most solvents when corrections for differences in ionic strength and free energy drive were made. Only nitromethane and acetonitrile exhibited marked deviations from linearity. Solvent properties such as viscosity, refractive index, surface tension, and density had little if any effect on the redox rate. The redox rate constants in the aprotic aromatic solvents, nitrobenzene, benzonitrile, and acetophenone paralleled the free energy drive of their respective reactions. No such trend was found with the other solvent groups. In fact, the polar solvents exhibited nearly the reverse trend. The kinetic results of this study have been interpreted in terms of the theoretical predictions of Marcus. The effects of ionic strength and ion pairing in the different solvents have also been discussed.

Disciplines

Chemistry | Physical Sciences and Mathematics

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