Identification and Kinetic Study of the Peroxymalonyl Radical in the Aerobic Oxidation of Malonic Acid by Cerium(IV)

Neumann, Bettina; Mueller, Stefan C.; Hauser, M.; Steinbock, Oliver; Simoyi, Reuben H.; Dalal, N. S.

doi:10.1021/ja00128a033

Cited by 42 publications

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“…14 In the malonic acid system, molecular oxygen was considered as a fast kinetical switch, influencing mainly the kinetics of Ce(IV) and the peroxymalonyl radical. The slow decay of the primary malonyl radical revealed therefore no significant dependence on the initial …”

Section: Discussionmentioning

confidence: 99%

Oxidation of Glyoxylic Acid by Cerium(IV): Oxygen-Induced Enhancement of the Primary Radical Concentration

et al. 1996

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In order to help understand the role of oxygen in Ce(IV)-induced oxidation of small carbonic acids, we investigated the reaction of glyoxylic acid (HCOCOOH) and Ce(IV) in 1 M sulfuric acid. Spectrophotometric data showed that in excess of glyoxylic acid the consumption of Ce(IV) obeys pseudo-first-order kinetics, with a rate constant of 8.8 L mol -1 s -1 at 25°C and an activation energy of 80 kJ mol -1 . Rapid-flow EPR measurements revealed an approximately 1:2:1 triplet with a g value of 2.0071 ( 0.0005 and a hyperfine splitting of 7.1 ( 0.2 G, assignable to the primary radical formed by abstraction of a hydrogen atom from hydrated glyoxylic acid. The rate constant for the anaerobic self-decay of the radical was measured as approximately 3.7 × 10 9 L mol -1 s -1 . Surprisingly, oxygen had no effect on the Ce(IV) kinetics, while the radical decay was significantly inhibited under aerobic conditions (ratio of experimental rate constants ≈6.3). Amperometric measurements revealed accompanying oxygen consumption. Analyses based on numerical simulations show that the observed oxygen-induced increase in radical concentration cannot be explained in the framework of standard autooxidation mechanisms. An alternative reaction scheme is suggested which reproduces the observed aerobic radical kinetics and which thus could be relevant to similar oxidation reactions.

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Section: Discussionmentioning

confidence: 99%

Oxidation of Glyoxylic Acid by Cerium(IV): Oxygen-Induced Enhancement of the Primary Radical Concentration

et al. 1996

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“…Reactions M15 -M18. For the reactions M15 and M16, involving radicals, we used as estimates the available values of the rate constants of the analogous reactions with malonic acid [30]. We choose the rate constant of reaction M17 in analogy with that of reaction M14.…”

Section: M7mentioning

confidence: 99%

Experimental and mechanistic study of the bromomalonic acid/bromate oscillating system catalyzed by [Fe(phen)3]2+

Benini¹,

Cervellati²,

Fetto³

1998

Int. J. Chem. Kinet.

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The oscillatory behavior of a -catalyzed/bromomalonic acid/acidicbromate Belousov-Zhabotinsky system in aerated batch conditions has been reinvestigated. An 18-step skeleton mechanism is proposed. Reactions involving oxygen in the aqueous phase as well as reactions involving organic radicals are included in the skeleton mechanism. The numerical treatment of the corresponding differential equations leads to simulated behaviors in satisfactory agreement with the experimental ones.

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“…Our study aims to efficiently incorporate the essence of recent advances regarding the mechanism of the organic subset of the BZ reaction. [16][17][18] These include, for instance, the identification of the peroxymalonyl radical and the investigation of the structure of branching pathways in the aerobic oxidation of malonic acid by cerium(IV).…”

Section: Introductionmentioning

confidence: 99%

Oxygen Inhibition of Oscillations in the Belousov−Zhabotinsky Reaction

2000

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The inhibitory effect of molecular oxygen on chemical oscillations in a semiclosed Belousov-Zhabotinsky system is investigated. Comparison of experimental results obtained from anaerobic and aerobic reactions shows that the oxygen-induced increase of oscillation periods is most pronounced at low concentrations of sulfuric acid or bromate and at high concentrations of malonic acid. Under the given experimental conditions, oxygen inhibition is negligible Based on the classical Oregonator, we propose an extended model that accounts for the observed concentration dependencies. This model treats oxygen as a dynamic variable and is capable of describing oxygen oscillations as well as the striking increase in oxygen concentration for conditions in which oscillations are fully suppressed. The rate equations of the extended Oregonator model are presented in a dimensionless form and are, for anaerobic conditions, in exact correspondence to the classical model.

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Identification and Kinetic Study of the Peroxymalonyl Radical in the Aerobic Oxidation of Malonic Acid by Cerium(IV)

Abstract: There is currently considerable interest in definitive characterization of organoperoxy radicals in aqueous media because these radicals seem to play key roles in many chemical (e.g., autoxidation) and biochemical (e.g., lipid peroxidation) reac-

Cited by 42 publications

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Oxidation of Glyoxylic Acid by Cerium(IV): Oxygen-Induced Enhancement of the Primary Radical Concentration

Oxidation of Glyoxylic Acid by Cerium(IV): Oxygen-Induced Enhancement of the Primary Radical Concentration

Experimental and mechanistic study of the bromomalonic acid/bromate oscillating system catalyzed by [Fe(phen)3]2+

Oxygen Inhibition of Oscillations in the Belousov−Zhabotinsky Reaction

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