TY - JOUR
T1 - Reactions of peroxyl radicals with Fe(H2O)62+
AU - Mansano-Weiss, Corin
AU - Cohen, Haim
AU - Meyerstein, Dan
N1 - Funding Information:
This study was supported in part by grants from the Israel Science Foundation and from the Budgeting and Planning Committee of The Council of Higher Education and the Israel Atomic Energy Commission. D. M. wishes to express his thanks to Mrs. Irene Evens for her ongoing interest and support.
PY - 2002/7/25
Y1 - 2002/7/25
N2 - 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.
AB - 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.
UR - https://www.scopus.com/pages/publications/0037173577
U2 - 10.1016/S0162-0134(02)00460-9
DO - 10.1016/S0162-0134(02)00460-9
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C2 - 12121776
AN - SCOPUS:0037173577
SN - 0162-0134
VL - 91
SP - 199
EP - 204
JO - Journal of Inorganic Biochemistry
JF - Journal of Inorganic Biochemistry
IS - 1
ER -