Studies of the reactions of iron(II) ascorbate mixtures with molecular oxygen in solution

Abstract

Mijssbauer and electronic absorbance spectrossopic studies on the reactions of iron(II):ascorbic acid with molecular oxygen in aqueous and methanolic solutions are reported. Both spectroscopic techniques show that in the starting mixtures there are no iron(II):ascorbate complexes. On mixing the iron- (II)/ascorbate solution with solutions containing molecular oxygen at pH 6-7 high spin iron(II1) is observed in the Mijssbauer spectrum. Coloured intermediates, the lifetimes of which are solvent dependent, are seen by stopped-flow spectrophotometry. We assign these coloured intermediates as iron(II1) ascorbate complexes. The stoichiometry of the initial reaction between iron(I1) and oxygen is shown to be 2Fe(II):02 by stopped-flow methods. A scheme for the overall reactions is discussed.