A kinetic and ESR investigation of iron(II) oxalate oxidation by hydrogen peroxide and dioxygen as a source of hydroxyl radicals
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A kinetic and ESR investigation of iron(II) oxalate oxidation by hydrogen peroxide and dioxygen as a source of hydroxyl radicals. / Park, J S; Wood, P M; Davies, Michael Jonathan; Gilbert, B C; Whitwood, A C.
In: Free Radical Research, Vol. 27, No. 5, 11.1997, p. 447-58.Research output: Contribution to journal › Journal article › peer-review
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TY - JOUR
T1 - A kinetic and ESR investigation of iron(II) oxalate oxidation by hydrogen peroxide and dioxygen as a source of hydroxyl radicals
AU - Park, J S
AU - Wood, P M
AU - Davies, Michael Jonathan
AU - Gilbert, B C
AU - Whitwood, A C
PY - 1997/11
Y1 - 1997/11
N2 - The reaction of Fe(II) oxalate with hydrogen peroxide and dioxygen was studied for oxalate concentrations up to 20 mM and pH 2-5, under which conditions mono- and bis-oxalate complexes (Fe[II](ox) and Fe[II](ox)2[2-]) and uncomplexed Fe2+ must be considered. The reaction of Fe(II) oxalate with hydrogen peroxide (Fe2+ + H2O2 --> Fe3+ + .OH + OH-) was monitored in continuous flow by ESR with t-butanol as a radical trap. The reaction is much faster than for uncomplexed Fe2+ and a rate constant, k = 1 x 10(4) M(-1) s(-1) is deduced for Fe(II)(ox). The reaction of Fe(II) oxalate with dioxygen is strongly pH dependent in a manner which indicates that the reactive species is Fe(II)(ox)2(2-), for which an apparent second order rate constant, k = 3.6 M(-1) s(-1), is deduced. Taken together, these results provide a mechanism for hydroxyl radical production in aqueous systems containing Fe(II) complexed by oxalate. Further ESR studies with DMPO as spin trap reveal that reaction of Fe(II) oxalate with hydrogen peroxide can also lead to formation of the carboxylate radical anion (CO2-), an assignment confirmed by photolysis of Fe(II) oxalate in the presence of DMPO.
AB - The reaction of Fe(II) oxalate with hydrogen peroxide and dioxygen was studied for oxalate concentrations up to 20 mM and pH 2-5, under which conditions mono- and bis-oxalate complexes (Fe[II](ox) and Fe[II](ox)2[2-]) and uncomplexed Fe2+ must be considered. The reaction of Fe(II) oxalate with hydrogen peroxide (Fe2+ + H2O2 --> Fe3+ + .OH + OH-) was monitored in continuous flow by ESR with t-butanol as a radical trap. The reaction is much faster than for uncomplexed Fe2+ and a rate constant, k = 1 x 10(4) M(-1) s(-1) is deduced for Fe(II)(ox). The reaction of Fe(II) oxalate with dioxygen is strongly pH dependent in a manner which indicates that the reactive species is Fe(II)(ox)2(2-), for which an apparent second order rate constant, k = 3.6 M(-1) s(-1), is deduced. Taken together, these results provide a mechanism for hydroxyl radical production in aqueous systems containing Fe(II) complexed by oxalate. Further ESR studies with DMPO as spin trap reveal that reaction of Fe(II) oxalate with hydrogen peroxide can also lead to formation of the carboxylate radical anion (CO2-), an assignment confirmed by photolysis of Fe(II) oxalate in the presence of DMPO.
KW - Cyclic N-Oxides
KW - Electron Spin Resonance Spectroscopy
KW - Ferrous Compounds
KW - Hydrogen Peroxide
KW - Hydrogen-Ion Concentration
KW - Hydroxyl Radical
KW - Kinetics
KW - Oxalates
KW - Oxalic Acid
KW - Oxidation-Reduction
KW - Oxygen
KW - Spin Labels
KW - Spin Trapping
KW - tert-Butyl Alcohol
M3 - Journal article
C2 - 9518062
VL - 27
SP - 447
EP - 458
JO - Free Radical Research
JF - Free Radical Research
SN - 1071-5762
IS - 5
ER -
ID: 138284996