Behavior of carbon trioxide (-) radicals generated in the flash photolysis of carbonatoamine complexes of cobalt(III) in aqueous solution

Chen, Schoen‐Nan; Cope, Virgil W.; Hoffman, Morton Z.

doi:10.1021/j100628a006

Cited by 139 publications

(50 citation statements)

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“…This indicates that either the proton hyperfine splitting constant of the carbonate radical is lower than 1 G or that the species is not protonated (see Reaction 11) over the studied pH range of 6 -9. Although the literature contains conflicting evidence regarding the protonated state of the carbonate radical over the 6 -12 pH range (36,37), recent studies by time resolved RAMAN spectroscopy have found no evidence for its protonation at pHs between 7.5 and 12.3 (38). These studies are in agreement with our EPR data indicating that the radical is not protonated at physiological pHs.…”

Section: Table I Epr Parameters Of the Carbonate Radical In Various Msupporting

confidence: 89%

Direct EPR Detection of the Carbonate Radical Anion Produced from Peroxynitrite and Carbon Dioxide

Bonini¹,

Radí²,

Ferrer-Sueta

et al. 1999

Journal of Biological Chemistry

295

220

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The biological effects of peroxynitrite have been recently considered to be largely dependent on its reaction with carbon dioxide, which is present in high concentrations in intra-and extracellular compartments. Peroxynitrite anion (ONOO ؊ ) reacts rapidly with carbon dioxide, forming an adduct, nitrosoperoxocarboxylate (ONOOCO 2 ؊ ), whose decomposition has been proposed to produce reactive intermediates such as the carbonate radical (CO 3 . ). Here, by the use of rapid mixing continuous flow electron paramagnetic resonance (EPR), we directly detected the carbonate radical in flow mixtures of peroxynitrite with bicarbonate-carbon dioxide over the pH range of 6 -9. The radical was unambiguously identified by its EPR parameters (g ‫؍‬ 2.0113; line width ‫؍‬ 5.5 G) and by experiments with bicarbonate labeled with 13 C. In this case, the singlet EPR signal obtained with 12 C bicarbonate splits into the expected doublet because of 13 C (a( 13 C)‫؍‬ 11.7 G). The singlet spectrum of the unlabeled radical was invariant between pH 6 and 9, confirming that in this pH range the detected radical is the carbonate radical anion (CO 3 . ).Importantly, in addition to contributing to the understanding of nitrosoperoxocarboxylate decomposition pathways, this is the first report unambiguously demonstrating the formation of the carbonate radical anion at physiological pHs by direct EPR spectroscopy.Peroxynitrite 1 is formed from the very fast reaction between nitric oxide and superoxide anion (k ϭ (6.7 Ϫ 19) ϫ 10 9 M Ϫ1 s Ϫ1 ) (see Reaction 1) (1, 2). The compound is a potent oxidant that has been receiving increasing attention as a potential pathogenic mediator in human diseases and as a cellular toxin in host defense mechanisms against invading microorganisms (3-6). At present, a significant part of the biological reactivity of peroxynitrite is ascribed to the adduct produced by its reaction with carbon dioxide (7-13). The peroxynitrite anion (ONOO Ϫ ), which is the predominant form at physiological pHs (pK a ϭ 6.8) (see reaction 2, Table II) (2, 3), reacts fast with carbon dioxide (pH-independent k ϭ 5.8 ϫ 10 4 M Ϫ1 ⅐ s Ϫ1 at 37°C) (11), producing an adduct whose structure is proposed to be ([ONOOCO 2 ] Ϫ , nitrosoperoxocarboxylate) (see reaction 3, Table II) (7). Taking into account the concentrations of carbon dioxide in equilibrium with bicarbonate present in physiological fluids, model calculations have suggested that most of the peroxynitrite that might be formed in these fluids will produce the carbon dioxide adduct before reacting with other biological targets (5, 13).Carbon dioxide modulates the reactivity of peroxynitrite by altering reaction rates, product yields, and product distribution (7-13). In these reactions, formation of the adduct nitrosoperoxocarboxylate is rate-limiting, as first proposed by Lymar and Hurst (7). This suggestion was confirmed by other authors (8 -13), and the current proposal is that in the absence of substrates, the carbon dioxide adduct decomposes to nitrate and carbon dioxide, but in ...

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Section: Table I Epr Parameters Of the Carbonate Radical In Various Msupporting

confidence: 89%

Direct EPR Detection of the Carbonate Radical Anion Produced from Peroxynitrite and Carbon Dioxide

Bonini¹,

Radí²,

Ferrer-Sueta

et al. 1999

Journal of Biological Chemistry

295

220

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“…The carbonate radical is characterized by a relatively high one‐electron reduction potential (1.59 V vs NHE [69]) but is generally much less reactive and more selective than · OH. Uncertainty has long existed whether its conjugated acid, the bicarbonate radical, could be important at pH values usually occurring in natural waters (its p K a was indirectly estimated to be 9.6 [70] and 7‐8.2 [71]), but a recent pulse‐radiolysis study provided convincing evidence that the bicarbonate radical's p K a is less than 0 [72]. Therefore, we will consider only the carbonate radical.…”

Section: Qsars Of Oxidants In Aqueous Solutionmentioning

confidence: 99%

Quantitative structure‐activity relationships for oxidation reactions of organic chemicals in water

Canonica

Tratnyek

2003

Enviro Toxic and Chemistry

109

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Abstract-Even in the absence of microbiological mediation, oxidation is one of the most important chemical processes contributing to the degradation of organic contaminants in the aquatic environment. The oxidants that are responsible for these reactions include hydroxyl radical, carbonate radical, organic oxyl and peroxyl radicals, peroxides, excited triplet states of organic chromophores, singlet molecular oxygen, ozone, chlorine dioxide, permanganate, and chromate. Some of these oxidants contribute to natural attenuation of organic contaminants, but many are of greater interest because of their role in engineered remediation technologies. Kinetic studies of these processes have lead to numerous quantitative structure-activity relationships (QSARs). Many of these QSARs are simple empirical correlations to common convenient descriptor variables like Hammett constants (), half-wave oxidation potentials (E ½ ), energies of the highest occupied molecular orbital (E HOMO ) or rate constants for other oxidation reactions. However, several environmentally relevant, aqueous-phase oxidation reactions have been described with QSARs based on theoretical models for electron transfer that were developed by Marcus-Hush and Rehm-Weller. This review summarizes many of the reported QSARs for aquatic oxidations of organic compounds with emphasis on the interrelation between traditional empirical models and the potential for future development of QSARs based on theoretical models.

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“…[2] with the permission of IUBMB). The methods include the radiolysis of solid salt matrices and aqueous solutions, oxidation of HCO 3 − by the sulfate radical anion, photolysis of carbonatoamine complexes, and flash photolysis of carbonate solutions [25][26][27][28][29][30][31]. 3.…”

Section: Oxidative Damagementioning

confidence: 99%

Reactive Inorganic Oxy‐Species of C, N, S, and P

Sharma¹

2012

Oxidation of Amino Acids, Peptides, and Proteins

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Behavior of carbon trioxide (-) radicals generated in the flash photolysis of carbonatoamine complexes of cobalt(III) in aqueous solution

Cited by 139 publications

References 3 publications

Direct EPR Detection of the Carbonate Radical Anion Produced from Peroxynitrite and Carbon Dioxide

Direct EPR Detection of the Carbonate Radical Anion Produced from Peroxynitrite and Carbon Dioxide

Quantitative structure‐activity relationships for oxidation reactions of organic chemicals in water

Reactive Inorganic Oxy‐Species of C, N, S, and P

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