Temperature coefficients of half-wave potentials and entropies of transfer of cations in aprotic solvents

Abstract

Temperature coefficients for the polarographic reductions of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Tl⁺, Cu⁺, Cu²⁺, Zn²⁺, Cd²⁺, Ba²⁺, Pb²⁺ bis(biphenyl) chromium(I) tetraphenylborate, ferrocene and perylene have been derived from measurements vs. the Ag/Ag⁺(0.01 mol dm^–3) electrodes kept at 25 °C in 0.1 mol dm^–3 solutions of tetrabutylammonium perchlorate in acetonitrile, N-methyl-2-pyrrolidone, N-methyl-2-thiopyrrolidone, pyridine and N,N-dimethylthioformamide. Data for Ag⁺ were obtained from potentiometric measurements. Entropies for the abovementioned redox couples and for Ag⁺ were calculated for reversible electrode reactions on the basis of the assumption of a negligible thermal diffusion potential. This assumption was also employed to calculate single-ion entropies of transfer from acetonitrile into N-methyl-2-pyrrolidone, N-methyl-2-thiopyrrolidone, pyridine and N,N-dimethylthioformamide.