Reactions between haemin and hydrogen peroxide. Part 1.—Ageing and non-destructive oxidation of haemin

Abstract

The absorption spectra of aqueous alkaline solutions of haemin, in contact with the atmosphere, change over a period of several hours. This “ageing” effect is an autoxidation, being first order with respect to haemin and approximately first order with respect to oxygen. pH effects indicate that haemin undergoes autoxidation much more rapidly than does haematin. Spectrophotometric measurements show that the product of ageing (designated haemin (A)) is also formed by the reaction of haemin with hydrogen peroxide. Failure to recognize formation of haemin(A) may lead to quantitative and, perhaps, qualitative errors in interpretation of kinetic data concerning the catalytic action of haemin.