The electrochemical behaviour of 1-Phenyl-3-pyrazolidone (Phenidone) has been investigated with different techniques (voltammetry, microcoulometry, potential-sweep chronoamperometry). The compound undergoes a monoelectronic oxidation on Hg electrodes. A second oxidation step is observed at Pt electrodes. The two oxidation waves merge at pH = 1.5. In order to ascertain the nature of the electrolysis products, macroscale electrolytic oxidation were performed potentiostatically and the electrolysed solutions analysed spectro-photometrically. It has thus been shown that the final oxidation product is 3-hydroxy-pyrazole, independently from the electrode potential; during electrolysis the red colour characteristic of the Phenidone free radical is formed. A direct proof that the primary oxidation product of Phenidone is a free radical, has been obtained by E. S. R. measurements. Potential sweep chronoamperometric curves of Phenidone show a kinetic character in suitable experimental conditions. This fact and the results of controlled potential electrolysis are in agreement with the hypothesis that the free radical undergoes a dismutation reaction.
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Con il contributo del Ministero per i Beni e le Attività Culturali