ELECTROCHEMICAL REDUCTION OF ALKALI METAL IONS IN PYRIDINE

Electrochemical reduction of pyridine solutions of the alkali metal ions was investigated, using polarography, cyclic voltammetry, coulometry and controlled potential electrolysis. Na(l), K(l), Rb(l) and Cs(l) are reversibly reduced at the DME and give a reversible cyclic voltammetric couple at the hanging mercury electrode. Reduction of Li(l), however, shows some degree of irreversibility at the DME, especially at higher concentrations. Cyclic voltammograms of Li(l) display a double reduction peak; the first peak height is directly proportional to Li(l) concentration and may involve reduction of a pyridine molecule in the Li(l) solvation sheath, rather than reduction of Li(l) to the metal amalgam; the second peak is proportional to the water and lithium contents and may involve reduction of pyridine in a (Pyr H,0) Li(l) species. The diffusion current constants are considerably smaller than those in water and can be correlated with the ionic conductance of alkali metal salts in pyridine. © 1969, American Chemical Society. All rights reserved.