ELECTROCHEMICAL DISK GENERATION AND RING IDENTIFICATION OF CARBANIONS FROM ORGANOMERCURIALS IN ACETONITRILE

A rotating disk-ring electrode was used for study of a series of organomercury compounds R2Hg, where R = CN, CF(NO2)2, C6F5, PhCC, p-NO2C6H4OCC, PhSCH2CC, PhCOCH2, CH2CN, CCl2CCl, 2-phenyl-o-carboranyl. Reduction of these compounds at a Pt-disk in acetonitrile is a two-electron process and results in generation of the carbanion R-. The carbanions generated at the disk interact with the solvent during their convective diffusion to the ring electrode where there may be oxidized. The main reaction in solution, shown using chromatography-mass spectrometry techniques, is acid-base interaction of carbanions with the solvent acetonitrile, which acts as a Brönsted acid. Reaching the ring, the carbanions may be oxidized at anodic potentials of the ring; oxidation potentials depend significantly on carbanion structure (e.g.+0.28 V (vs. SCE), for PhCC- and +2.20 V for CN-. It is shown that PKa value of the carbanions do not correlate with the oxidation potentials, however, a linear correlation is observed between pKa values and a special parameter called the efficiency coefficient. © 1979.