Reactions of peroxyl radicals with Fe(H2O)62+

Corin Mansano-Weiss, Haim Cohen, Dan Meyerstein

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30 Scopus citations

Abstract

The reactions of RO2 radicals with Fe(H2O)62+ were studied, R=H; CH3; CH2COOH; CH2CN; CH2C(CH3)2OH; CH2OH; CHCl2/CCl3. All these processes involve the following reactions:(1)Fe(H2O)62+ +RO2⇄(H2O)5 FeIII-OOR2+K 1∼250 M-1(2)(H2O)5 FeIII-OOR2+ +H3O+/H2 O→Fe(H2O)63+ +ROOH+H2O/OH- (3)(H2O)5FeIII- OOR2++2Fe(H2O)62+→ 3Fe(H2O)63++ROH(4)2 RO2→ Products(5)RO2+(H2O)5 FeIII-OOR2+→ Fe(H2O)62++productsThe values of k1 and k3 [reaction (3) is clearly not an elementary reaction] approach the ligand exchange rate of Fe(H2O)62+, i.e. these reactions follow an inner sphere mechanism and the rate determining step is the ligand exchange step. The rate of reaction (3) is several orders of magnitude faster than that of the Fenton reaction.Surprisingly enough the K1 values are nearly independent of the redox potential of the radical and are considerably higher than calculated from the relevant redox potentials. These results indicate that the ROO- ligands considerably stabilise the Fe(III) complex, this stabilisation is smaller for radicals with electron withdrawing groups which raise the redox potential of the radical but decrease the basicity of the ROO- ligands, two effects which seem to nearly cancel each other. Finally, the results clearly indicate that reaction (5) is relatively fast and affects the nature of the final products. The contribution of these reactions to oxidation processes involving 'Fenton-like' processes is discussed.

Original languageEnglish
Pages (from-to)199-204
Number of pages6
JournalJournal of Inorganic Biochemistry
Volume91
Issue number1
DOIs
StatePublished - 25 Jul 2002

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