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Simultaneous electrochemical and EPR studies of flavin radical equilibria
Author(s) -
Male Roxanne,
Samotowka Michael A.,
Allendoerfer Robert D.
Publication year - 1989
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.1140010409
Subject(s) - comproportionation , chemistry , electron paramagnetic resonance , aqueous solution , electrolysis , nitrobenzene , inorganic chemistry , solvent , equilibrium constant , radical , standard electrode potential , photochemistry , flavin group , electrochemistry , electrode , organic chemistry , physics , nuclear magnetic resonance , electrolyte , enzyme , catalysis
The comproportionation reaction of the oxidized and reduced forms of both riboflavin and lumiflavin to form their respective radicals is studied over a range of pHs in aqueous solution and in the aprotic solvent methylene chloride. The comproportionation equilibrium constant is reported for basic solutions reduced at an amalgamated Au electrode, where adsorption does not interfere with equilibrium measurements, with both Na + and Ca 2+ as the counterion. The basic and nonaqueous solution voltammetries of riboflavin and lumiflavin are shown to be similar by measuring the radical concentration by electron paramagnetic resonance (EPR) during an in situ electrolysis as a function of potential. In both solvent systems the first of the two reduction waves corresponds to a two‐electron reduction with the radical present formed by comproportionation.