The Fenton Reaction in Aerated Aqueous Solutions Revisited

Abstract

The oxidation of alcohols in aerated acidic aqueous solutions by the Fenton reagent is a chain reaction. The length of the chain depends linearly on the number of CHnOR (n = 1 or 2) groups in the alcohol. The reaction is accelerated by increasing the concentration of Fe(H2O)62+, but this cation is also active in at least one of the termination steps of the chain reaction. Addition of ethanol to a solution containing sucrose shortens the chain length. Saturation with dioxygen, instead of air, increases the chain length. An increase in alcohol concentration increases the chain length up to a limiting value. A complicated mechanism, which is in agreement with all these observations, is proposed. However, efforts to simulate the mechanism succeed only in simulating the Fe(H2O)63+ yield, but indicate that the observed process is considerably faster than the predicted one. In the latter the rate‐determining step is the Fenton reaction, the rate constant of which is well known. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Avoiding high-valent iron intermediates: Superoxide reductase and rubrerythrin

“…An investigation under more physiologically relevant conditions showed that the reaction between Fe II ðaqÞ and H 2 O 2 apparently occurs rapidly enough (within the range of 10 3 -10 4 M À1 s À1 at pH 7 and 37°C) to be capable of causing significant, and even lethal damage if DNA repair enzymes are knocked out and/or the steady-state level of H 2 O 2 is not controlled [21]. Whether this higher second-order rate constant represents reaction (2) only and excludes autocatalytic oxidation of Fe II ðaqÞ is unclear, however [25,26]. In any case, iron-sulfur cluster and DNA damage due to this ''in vivo superoxide-driven Fenton chemistry'' is believed to be the predominant contributor to intracellular oxidative stress in bacteria [27][28][29].…”

Products of Cu(II)-catalyzed oxidation of the N-terminal fragments of α-synuclein in the presence of hydrogen peroxide

“…It is assumed that hydrogen peroxide reduces peptide-Cu(II) to peptide-Cu(I), this is followed by the reaction of Cu(I) with hydrogen peroxide to give Å OH [28]. However, it should be mentioned that the study clearly demonstrates that the mechanism of the Fenton reaction and Fenton-like reactions, in aerated solutions containing organic substrates, is considerable more complex than assumed earlier [29,30].…”

Nonheme Iron‐Oxo‐Catalyzed Methane Formation from Methyl Thioethers: Scope, Mechanism, and Relevance for Natural Systems

“…[7] That is, the second approximately 400-fold slower reactionh as, under the given experimental conditions, ah alf-life in the region of seconds. Assuming that the first ap-proximately 260 nmol mL À1 of CH 3 radicals produced are quenched by O 2 to yield to al arge extent the observedM eOH (see also MeOH quantification below), [54] the effective yield of CH 3 radicals in the reactions reported in Ta ble 1i sm uch larger (over 50 %). Assuming that the first ap-proximately 260 nmol mL À1 of CH 3 radicals produced are quenched by O 2 to yield to al arge extent the observedM eOH (see also MeOH quantification below), [54] the effective yield of CH 3 radicals in the reactions reported in Ta ble 1i sm uch larger (over 50 %).…”