Phenidone (1-Phenyl-3-Pyrazolidone): Oxidation

Analysis of polarographic data in the range pH 2-12 shows that Phenidone is oxidized to the neutral radical obtained by abstraction of one hydrogen atom. Phenidone is a monobasic weak acid of pK 9.35 (K=4.5x10^-10). The oxidation-reduction potential is given by $$E_{1/2}=E_{\circ }+\frac{RT}{F}in\left(K+[H+]\right)$$ where E_˚-0.688 on the normal hydrogen scale at 20° C. Electron Spin Resonance spectra confirm that the oxidation product is a free radical.