Redox properties of naturally occurring naphthoquinones: Vitamin K2(20) and lapachol
Redox properties of two naturally occurring naphthoquinones, vitamin K2(20) and lapochol, are examined by thin-layer voltammetry on a pyrolytic graphite electrode. The pH-potential diagrams of these compounds are plotted. In aqueous solutions, the quinones are shown to exist each in five forms. Thermodynamic parameters for all redox and acid-base equilibria between conjugated forms are determined. In contrast to lapachol, vitamin K2(20) forms, during its reduction, a large amount of stable semiquinone in a wide pH interval
KeywordsQuinone Redox Property Naphthoquinones Pyrolytic Graphite Electrode Lapachol
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