J. Rusling, P. Zuman
Nov 25, 1986
Citations
0
Influential Citations
15
Citations
Journal
Journal of Electroanalytical Chemistry
Abstract
Abstract The electroreductions and electrooxidations of 2-, 3-, and 4-pyridinecarboxaldehyde have been investigated in solutions of sodium hydroxide of concentration up to 10 M (J = 16.7) using dc and differential pulse polarography, linear sweep voltammetry, and controlled potential electrolysis. Both reductions and oxidations of these compounds were influenced by the formation of geminal diol anions (PyCH(OH)O−) in the bulk of the solution and in the vicinity of the electrode. The electroreductions of the 3- and 4-aldehydes proceed by a one-electron uptake, followed by a radical dimerization yielding pinacols. The two-electron reduction of the 2-aldehyde is complicated by competing dimerization and polymerization. In strongly alkaline solutions, the Cannizzaro reaction completes with bulk electrolysis. To undergo a two-electron oxidation in alkaline media to pyridinecarboxylic acids, pyridinecarboxaldehydes must be converted into PyCH(OH)O−. At J− At J−> 14 the geminal diol anion reacts with another hydroxide ion. This reaction results in a shift of half-wave potentials of the anodic wave to more negative values with incrasing aOH−.