Branched-chain mechanism in electrolytical reduction of some aryl alkyl ketones on mercury electrodes

• Published in: Journal of electroanalytical chemistry and interfacial electrochemistry 1971-01, Vol.32 (3), p.445-455
• Main Authors: Volke, J., Ryvolová-Kejharová, A., Manoušek, O., Wasilewski, L.
• Format: Article
• Language: English
• ISSN: 0022-0728
• DOI: 10.1016/S0022-0728(71)80147-X

The polarographic behaviour of simple aryl alkyl ketones, p-fluorinated aryl alkyl ketones, and complex p-fluorinated psychotropic aryl alkyl ketones confirms that, depending on pH and potential, after the uptake of the first electron the radical thus formed can either be further reduced to alcohol, or dimerize, or react with the electrode and form a mercury compound. Coulometric measurements at a stirred mercury electrode at pH 8.5 reveal a change in the number of electrons n app consumed at different potentials for the p-fluorinated aryl alkyl ketones. The values of n app vary from 1.01 at the potential of the foot of the wave to 1.54 on the limiting current for p-fluorobutyrophenone, and from 1.20 to 1.70 or 1.31 to 1.81 for p-fluoropropiophenone and p-fluoroacetophenone, respectively. Thus, in large scale reductions on the mercury pool, the two-electron reduction to alcohol prevails at the potential of the limiting current whereas at the potential of the rising portion of the wave dimer formation proceeds to an appreciable extent. However, the polarographic values of n obtained by measuring the limiting current with a dropping mercury electrode are lower since either the primary radical has more time for dimerization or dimer formation is supported by adsorption on the dropping mercury electrode.