REDOX PROPERTIES OF NAPHTHAZARIN AND ISONAPHTHAZARIN

Redox properties of naphthazarin, polyhydroxynaphthoquinone originated from plants, and its isomer are studied by thin layer voltammetry on a pyrographite electrode. The experimental data are presented in the f orm of the pH vs. potential diagrams. Five forms of naphthazarin and f our forms of isonaphthazarin are found in aqueous solutions. Thermodyn amic parameters of redox and acid-base equilibria between conjugated f orms of these compounds are determined. During electrochemical oxidati on, naphthazarin and its isomer yield different products: naphthodiqui none and tetraketotetralin, respectively.