关键词: 马蔺子素, 极谱催化波, 半醌自由基, K₂S₂O₈

Abstract: The voltammetric behavior and the production mechanism of polarographic catalytic wave of irisquinone were studied by linear potential scan polarography, cyclic voltammetry, UV spectroscopy and constant potential electrolysis in both aqueous and N,N dimethyl formamide(DMF) media. In Na₂B₄O₇ KH₂PO₄(pH=7.7) buffer, the quinonyl group of irisquinone was first reduced in a 1e^-, 1H⁺ process to produce an intermediate free radical semiquinone, and the further reduction of the free radical semiquinone to the corresponding hydroquinone anion in the same way was accompanied by its chemical reaction. In DMF tetraethyl ammonium bromide(TEAB) media, the reduction of irisquinone was two successive single electron processes without the chemical reaction of the free radical semiquinone. All these processes yield the reversible reduction wave of irisquinone. When S₂O₈^2- was present, the free radical semiquinone of irisquinone was oxidized to regenerate the original quinonyl group, which resulted in the production of a polarographic catalytic wave. The apparent first order rate constant k_f of the oxidation reaction of the free radical semiquinone of irisquinone with S₂O₈^2- was 3.3×10⁶ L·mol^-1 ·s^-1.

Key words: Irisquinone, Polarographic catalytic wave, Semiquinone free radical, Persulfate