Fenton-like Chemistry in Water: Oxidation Catalysis by Fe(III) and H2O2

The formation of active intermediates from the Fenton-like reagent (a mixture of iron(III) ions and hydrogen peroxide) in aqueous solution has been investigated using static DFT calculations and Car−Parrinello molecular dynamics simulations. We show the spontaneous formation of the iron(III) hydroperoxo intermediate in a first step. The Fenton-like reaction thus proceeds very differently compared to Fenton's reagent (i.e., the FeII/H2O2 mixture), for which we have recently shown that the first step is the spontaneous O−O lysis of hydrogen peroxide when coordinated to iron(II) in water. For the second step in the reaction mechanism of the Fenton-like reagent, we compare the possibilities of homolysis and heterolysis of the O−O bond and the Fe−O bond of the produced [(H2O)5FeIIIOOH]2+ intermediate. We find that concomitant hydrolysis of the reacting species plays a crucial role and, taking this into account, that O−O homolysis ([(H2O)4(OH)FeIIIOOH]+ → [(H2O)4(OH)FeIVO]+ + OH•) in vacuo is a likely second st...