Reactions of peroxyl radicals with Fe(H2O)62+

Corin Mansano-Weiss; Haim Cohen; Dan Meyerstein

doi:10.1016/s0162-0134(02)00460-9

Reactions of peroxyl radicals with Fe(H₂O)₆²⁺

Corin Mansano-Weiss, Haim Cohen, Dan Meyerstein

Research output: Contribution to journal › Article › peer-review

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 Fe^III-OOR²⁺K ₁∼250 M^-1(2)(H₂O)₅ Fe^III-OOR²⁺ +H₃O⁺/H₂ O→Fe(H₂O)₆³⁺ +ROOH+H₂O/OH^- (3)(H₂O)₅Fe^III- OOR²⁺+2Fe(H₂O)₆²⁺→ 3Fe(H₂O)₆³⁺+ROH(4)2 RO₂^•→ Products(5)RO₂^•+(H₂O)₅ Fe^III-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 language	English
Pages (from-to)	199-204
Number of pages	6
Journal	Journal of Inorganic Biochemistry
Volume	91
Issue number	1
DOIs	https://doi.org/10.1016/s0162-0134(02)00460-9
State	Published - 25 Jul 2002
Externally published	Yes

Bibliographical note

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.

Funding

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.

Funders	Funder number
Israel Science Foundation
Planning and Budgeting Committee of the Council for Higher Education of Israel
Israel Atomic Energy Commission

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10.1016/s0162-0134(02)00460-9

Cite this

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title = "Reactions of peroxyl radicals with Fe(H2O)62+",

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.",

author = "Corin Mansano-Weiss and Haim Cohen and Dan Meyerstein",

note = "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.",

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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.

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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.

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