The reaction of superoxide radical with iron complexes of EDTA studied by pulse radiolysis.
The reactions of Fe3+-EDTA and Fe2+-EDTA with O2- and CO2- were investigated in the pH range 3.8--11.8. Around neutral pH O2- reduces Fe3+-EDTA with a rate constant which is pH dependent kpH 5.8--8.1 = 2 - 10(6)--5 - 10(5) M-1 - s-1. At higher pH values this reaction becomes much slower. The CO2- radical reduces Fe3+-EDTA with kpH 3.8--1- = 5 +/- 1 - 10(7) M-1 - s-1 independent of pH. At pH 9--11.8, Fe2+-EDTA forms a complex with O2- with kFe2+-EDTA + O2 = 2 - 10(6)--4 - 10(6) M-1 - s-1 which is pH dependent. We measured the spectrum of Fe2+-EDTA-O2- and calculated epsilon 290 over max = 6400 +/- 800 M-1 - cm-1 in air-saturated solutions. In O2-saturated solutions another species is formed with a rate constant of 7 +/- 2 s-1. This intermediate absorbs around 300 nm but we were not able to identify it.
D004492:Edetic Acid; D005609:Free Radicals; D006863:Hydrogen-Ion Concentration; D007501:Iron; D007700:Kinetics; D008433:Mathematics; D010084:Oxidation-Reduction; D010100:Oxygen; D011675:Pulse Radiolysis; D013056:Spectrophotometry, Ultraviolet; D013481:Superoxides
D005609:Free Radicals; D013481:Superoxides; D004492:Edetic Acid; D007501:Iron; D010100:Oxygen