Reactions of peroxy acids with deuteroferrihaem

Abstract

Deuteroferrihaem reacts with m-chloroperoxybenzoic acid and monoperoxosulfate in a 2 : 1 stoichiometry whilst it reacts with peroxyacetic acid in a 4 : 1 stoichiometry. The UV/VIS spectra of the haem intermediates appear to be the same in all cases despite the different stoichiometries. The reaction of deuteroferrihaem and monoperoxosulfate is slow enough to obtain repetitive UV/VIS spectrophotometric scans during the formation of the intermediate as well as the regeneration of the ferrihaem. It is notable that, even with a significant initial excess of peroxy acid, ferrihaem regeneration proceeds immediately after intermediate formation. Thus there is no peroxy acid turnover phase. Instead the build up of a primary degradation product characterised by a broad absorbance band in the visible is observed at higher peroxy acid concentrations. A kinetic scheme for the formation of the intermediate and regeneration of ferrihaem is described that explains the amount of intermediate formation and the rate and extent of haem regeneration as a function of the nature and concentration of the peroxy acid.