Quantitative description of the chloride effect on chlorine dioxide generation from the ClO<sub>2</sub>‐HOCl reaction

Yin, Guohong; Ni, Yonghao

doi:10.1002/cjce.5450760509

Cited by 8 publications

(11 citation statements)

References 10 publications

(18 reference statements)

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“…The actual parameters that we are able to calculate are the products of the equilibrium constant K 1 and the rate constants k 2 and k 2 ‘. Although elimination of the pH-dependent path does not increase the average deviation significantly (see Table ), we have kept this process in the final model, because decreasing the pH increases the rate of decomposition of chlorous acid even in solutions containing 0.5−4.5 M sulfuric acid. , Our fitted values for K 1 k 2 and K 1 k 2 ‘ yield a rate constant (0.00175 + 0.00244[H + ]) M -1 s -1 for reaction 2 that is below that of Kieffer and Gordon, 0.0117 M -1 s -1 , and close to that of Hong and Rapson, 0.00275 M -1 s -1 in the pH range of interest.…”

Section: Discussionmentioning

confidence: 99%

“…The two most comprehensive efforts 5,6 to unravel the mechanism of the noncatalytic decomposition of chlorous acid are based on initial rate studies, not on the complete concentration−time series. More recently, the decomposition of chlorous acid has been studied at high acidity (4.5 M sulfuric acid solution), and the effect of chloride ion on chlorine dioxide formation has been discussed. , Except in the studies of Kieffer and Gordon, only the concentration of chlorine dioxide was followed.…”

Section: Mechanismmentioning

confidence: 99%

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Kinetics and Mechanism of the Decomposition of Chlorous Acid

et al. 2003

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The kinetics of decomposition of aqueous chlorous acid has been reinvestigated at pH 0.7-1.9, ionic strength 1.0 M (HSO 4 -/SO 4 2-), and temperature 25.0 ( 0.1°C. Optical absorbances were collected in the 240-450 nm wavelength range for up to ∼90% decomposition for time series lasting as long as 2 days. The number of absorbing species was investigated by matrix rank analysis; no absorbing intermediate was formed in significant concentration during the decomposition. Of the many mechanistic models tested, the one that fit best included the following reactive intermediates: HOCl, explains the variation in stoichiometric ratio as well as the maximum observed in the initial rate of ClO 2 formation as a function of pH. The kinetics of chlorous acid decomposition cannot be quantitatively fit through the last stages of the reaction without postulating a first-order decomposition. Scission of chlorous acid to give short-lived hydroxyl and chlorine-(II) monoxide is a plausible route for this process. A set of best-fit and literature-derived parameters is presented for the complete mechanism.

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Section: Discussionmentioning

confidence: 99%

Section: Mechanismmentioning

confidence: 99%

Kinetics and Mechanism of the Decomposition of Chlorous Acid

et al. 2003

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“…The results presented here demonstrate a similar effect of the chloride ion in the chlorine dioxide−tetrathionate reaction. The effect of chloride ion on the chlorine dioxide−hypochlorous acid reaction is also well-established . More recently, the role of Cl - has been discussed in the aqueous chlorine−chlorite reaction .…”

Section: Discussionmentioning

confidence: 99%

Kinetics and Mechanism of the Chlorine Dioxide-Tetrathionate Reaction

2003

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The chlorine-dioxide-tetrathionate reaction was studied spectrophotometrically in the pH range 4.55-5.55 at 25.0 ( 0.2 °C and 0.5 M ionic strength adjusted with sodium acetate as a buffer component. The stoichiometry was found to be S 4 O 6 2-+ 4 • ClO 2 + 5H 2 O f 4SO 4 2-+ ClO 3 -+ 3Cl -+ 10H + with small deviations at high excess of chlorine dioxide with no chloride ion initially present. The initial presence of chloride not only affects the stoichiometry but also accelerates the reaction. A 14-step mechanism, including four known and two newly proposed intermediates, is suggested to describe the observed behavior of the system.

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“…There has been some debate in oxychlorine kinetics on the reaction of chlorite and chloride: 117,118 ClO 2 -+ Cl -+ 2H + → 2HOCl R4.16 Thus bromate oxidations are catalyzed by addition of bromide. Figure 4.14, however,…”

Section: Effect Of Chloridementioning

confidence: 99%

Biomimetic Tools in Oxidative Metabolism: Characterization of Reactive Metabolites from Antithyroid Drugs

Chipiso¹

2000

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Toxicities of sulfur-based drugs have been attributed to formation of highly reactive sulfur oxo-acids and depletion of glutathione by the formation of reactive metabolites. Metabolic activation of these sulfur centers to conceivably toxic reactive metabolites (RMs) that can covalently modify proteins is considered the initial step in drug-induced toxicity. Despite considerable effort and research, detection and characterization of these RMs during drug development and therapy remains a challenge. Methimazole (MMI) and 6-propyl-2-thiouracil (PTU) are two commonly used antithyroid, sulfur-based drugs. Though effective, these drugs are associated with idiosyncratic toxicity. PTU has acquired a black box warning and physicians are calling for its withdrawal. RMs resulting from bioactivation of these drugs have been implicated in the aforementioned adverse reactions. Unfortunately, isolating and detecting RMs using traditional analytical techniques has not been successful due to their high reactivity and short life span, typically less than a minute. Current approaches in drug metabolism studies use microsomal incubations to generate RMs, which are then trapped using nucleophiles. Antithyroid drugs, however, are known to deactivate enzymes involved in their oxidation. Moreover, due to the complex nature of biological matrices and low abundance of possible toxic conjugates, this technique results in poor selectivity and sensitivity. This study developed and optimized an analytical method based on coupling electrochemical redox reactions and mass spectrometry to generate, detect and identify RMs from antithyroid drugs. The metabolites were also compared to those that were generated using chemical oxidants and I would also want to thank the members of my dissertation committee: Drs.

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Quantitative description of the chloride effect on chlorine dioxide generation from the ClO₂‐HOCl reaction

Cited by 8 publications

References 10 publications

Kinetics and Mechanism of the Decomposition of Chlorous Acid

Kinetics and Mechanism of the Decomposition of Chlorous Acid

Kinetics and Mechanism of the Chlorine Dioxide-Tetrathionate Reaction

Biomimetic Tools in Oxidative Metabolism: Characterization of Reactive Metabolites from Antithyroid Drugs

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Quantitative description of the chloride effect on chlorine dioxide generation from the ClO2‐HOCl reaction

Cited by 8 publications

References 10 publications

Kinetics and Mechanism of the Decomposition of Chlorous Acid

Kinetics and Mechanism of the Decomposition of Chlorous Acid

Kinetics and Mechanism of the Chlorine Dioxide-Tetrathionate Reaction

Biomimetic Tools in Oxidative Metabolism: Characterization of Reactive Metabolites from Antithyroid Drugs

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Product

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Quantitative description of the chloride effect on chlorine dioxide generation from the ClO₂‐HOCl reaction