ELECTROCHEMICAL REDUCTION OF N-ALKYLPYRIDINIUM SALTS AND THEIR METHYL-SUBSTITUTED DERIVATIVES IN SINGLE-PHASE AND 2-PHASE SYSTEMS

The electroreduction of N-alkylpyridinium cations and their methyl-sub stituted derivatives N-R1C5H4R2N+ (R1 = CH3, C2H5, C4H9, and C10H21; R 2 = H and CH3) in water-alcohol alkaline solutions was studied by the rotating ring-disc electrode method together with potentiodynamic meas urements on individual electrodes (glassy carbon) of the disc-ring sys tem. It was shown that in each case the process leads to the formation of a single dimeric product with a quantitative yield of the charge-t ransfer complex type. Dimers synthesized in a polar medium have a limi ted solubility; they can be formed on the cathode as a solid deposit a nd easily oxidized on the anode to initial alkylpyridinium cations. Pr eparative electrolysis was accomplished for an N-ethylpyridinium salt in a two-phase system in NaOH aqueous solution-benzene on cadmium, cop per, and lead cathodes. In contrast to electrolysis products with a ba se of single-phase aqueous solution, the liquid product that was separ ated from the organic phase after the solvent was removed by distillat ion is also dimeric, but with the following composition: 1,1'-diethyl- 1, 1',4,4'-tetrahydro-4,4'-dipyridyl. The latter is oxidized by sulfur dioxide to dipyridyl cations without breaking the carbon-carbon bond. A similar result was obtained at the reduction of an ethylpyridinium salt by a sodium amalgam.