A re-examination of temperature dependent reduction potentials of quinones from the point of view of the isokinetic relationship

Abstract

Temperature dependent half-wave potentials for the reversible reduction of 1,4-benzoquinone, 1,4-naphthoquinone, 9,10-anthraquinone, and 5,12-tetracenequinone in N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, propylene carbonate and acetonitrile are used as experimental examples for investigating the isokinetic relationship in heterogeneous electrochemical systems. Isokinetic behavior is found for each of the quinones on varying the solvent with the exception of acetonitrile. Based on results reported in previous papers of this series the isokinetic temperature is interpreted as being related to heat bath frequencies active in reactant solvent interactions and the significance of the absence of a matching frequency in the ir spectrum of acetonitrile is discussed. Thermodynamic arguments are applied to a relationship between the isokinetic half-wave potentials and gas phase electron affinities.