A stopped-flow study of the oxidation raction of ascorbic acid with chromic acid

Banaś, B.

doi:10.1016/s0020-1693(00)84725-8

Cited by 17 publications

(7 citation statements)

References 23 publications

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“…Hence, those two mechanisms may be considered for the oxidation of PEG by Cr(VI) with formation of either Cr V and/or Cr IV intermediate species 19,45,46 The decrease in the rates of oxidation on the addition of the Mn 2+ ion to the reaction mixtures may be considered as an indirect evidence for involvement of chromium(IV) as an intermediate species rather than that of chromium(V) species during the progress of such present redox reaction. 42,43 Under our experimental conditions of [H + ] used, the observed non-integral second-order dependence in [H + ] is reasonable when taking the protolytic equilibrium constant (K) values for Cr(VI) into consideration 45,47,48 as well as that the quantity of formation of the chromium dimer is negligibly small. This means that chromic acid can be assumed to be the main reactive species of the chromium ion, which confirmed by the calculated quantity of the formed H 2 CrO 4 using the values of K 45,47,48 (80−95% of [Cr(VI)] T ).…”

supporting

confidence: 53%

“…42,43 Under our experimental conditions of [H + ] used, the observed non-integral second-order dependence in [H + ] is reasonable when taking the protolytic equilibrium constant (K) values for Cr(VI) into consideration 45,47,48 as well as that the quantity of formation of the chromium dimer is negligibly small. This means that chromic acid can be assumed to be the main reactive species of the chromium ion, which confirmed by the calculated quantity of the formed H 2 CrO 4 using the values of K 45,47,48 (80−95% of [Cr(VI)] T ).…”

supporting

confidence: 53%

“…Generally, the values of activation entropies, Δ S ≠ , for redox reactions of innersphere nature were reported to be of negative signs, whereas that of positive Δ S ≠ values were usually refer to redox reactions of outersphere mechanisms. − Consequently, the observed negatively Δ S ≠ values in Table may indicate the predomination of the innersphere mechanism than that of the outersphere type for reduction of chromic acid by the PEG substrate.…”

Section: Discussionmentioning

confidence: 99%

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Promising Biocompatible, Biodegradable, and Inert Polymers for Purification of Wastewater by Simultaneous Removal of Carcinogenic Cr(VI) and Present Toxic Heavy Metal Cations: Reduction of Chromium(VI) by Poly(ethylene glycol) in Aqueous Perchlorate Solutions

et al. 2020

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A spectrophotometric technique has been applied for studying the reduction of chromium(VI) by poly(ethylene glycol) (PEG) as water-soluble and nontoxic synthetic polymer at a constant ionic strength of 4.0 mol dm −3 in the absence and presence of the ruthenium(III) catalyst. In the absence of the catalyst, the reaction orders in [Cr(VI)] and [PEG] were found to be unity and fractional first orders, respectively. The oxidation process was found to be acid-catalyzed with fractional second order in [H + ]. The addition of Ru(III) was found to catalyze the oxidation rates with observation of zero-order reaction in [CrO 42− ] and fractional orders in both [PEG] and [Ru(III)], respectively. The PEG reduces the soluble toxic hexavalent Cr(VI) as a model pollutant to the insoluble nontoxic Cr(III) complex, which is known to be eco-friendly and more safer from the environmental points of view. The acid derivative of PEG was found to possess high affinity for the removal of poisonous heavy metal ions from contaminant matters by chelation. Formation of the 1:1 intermediate complex has been kinetically revealed. A consistent reaction mechanism of oxidation was postulated and discussed.

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confidence: 53%

supporting

confidence: 53%

Section: Discussionmentioning

confidence: 99%

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Promising Biocompatible, Biodegradable, and Inert Polymers for Purification of Wastewater by Simultaneous Removal of Carcinogenic Cr(VI) and Present Toxic Heavy Metal Cations: Reduction of Chromium(VI) by Poly(ethylene glycol) in Aqueous Perchlorate Solutions

et al. 2020

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“…Of a special interest and relation to the present work, several papers have been published on kinetics study of oxidation by potassium dichromate in its different forms. In particular, kinetics of oxidation of various substrates by chromic acid has been reported [2][3][4][5][6][7][8][9][10][11][12]. Reaction kinetics of oxidation of atropine by alkaline potassium permanganate has been investigated recently [13].…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Oxidation of Atropine by K2Cr2O7 in Acidic Aqueous Solutions

Abdel-Halim¹,

Saleh²,

Al-Ghreizat³

2018

Asian J. Chem.

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Oxidation of atropine (ATN) by K2Cr2O7 has been studied kinetically in aqueous strongly acidic solutions. The kinetics of this reaction was investigated at different temperatures. A constant pH and constant ionic strength were maintained constant throughout all measurements. The concentration of atropine was around an order of magnitude greater than that of K2Cr2O7, that is under pseudo first order kinetics. Rate constants were obtained by monitoring change in absorbance of K2Cr2O7 with time at its predetermined maximum wavelength. Overall rate constant and the orders of the reaction in terms of concentrations of both atropine and K2Cr2O7 were determined. Reaction runs at different temperature allows activation energy of the process to be convoluted from temperature effect on the rate of the reaction. A resonable mechanism for the reaction was proposed in accordance with kinetics results.

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“…[6][7][8] As a result, the reactions of cellular components, including amino acids, ascorbic acid, carboxylic acids and other important low-molecular-weight substrates with chromate have since been researched and documented. [6][7][8][9][10] It is worthy of note that no previous work has utilised any co-ordinated chromium() ion for similar redox reactions. As a result, its oxidising properties while ligated have remained largely untested.…”

mentioning

confidence: 99%

Mechanism of oxidation of L-ascorbic acid by the pentaamminechromatocobalt(III) complex ion in aqueous solution

Dixon¹,

Dasgupta²,

Sadler³

1997

J. Chem. Soc., Dalton Trans.

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Oxidation of -ascorbic acid by pentaamminechromatocobalt() nitrate has been investigated over the ranges 6.1 р pH р 8.7, 21.0 р θ р 30.0 ЊC, in excess of -ascorbic acid at a constant ionic strength of 0.50 mol dm Ϫ3 (NaClO 4 ). Overall the reaction occurs in two distinct stages. The first, involving saturation kinetics, proceeds with an increase in absorbance at wavelengths 350-390 nm. During this stage the pentaamminechromato complex and the ascorbate anion react via an outer-sphere mechanism to form an ion pair. The rate equation for this stage is (i)with [A] T being total ascorbate, K 4 and k 5 are the equilibrium constant for adduct formation and first-order rate constant for its decomposition, respectively. At 25.0 ЊC, k 5 and K 4 have respective values of (3.5 ± 0.4) × 10 Ϫ2 s Ϫ1 and (8.5 ± 1.7) × 10 2 dm 3 mol Ϫ1 . The second stage involving a decrease in absorbance at similar wavelengths is the reduction of the free chromium() ion which is postulated to have been formed during the first stage of the reaction. The pseudo-first-order rate constant for this stage can be expressed as in equation (ii) where K 1 and K 6

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A stopped-flow study of the oxidation raction of ascorbic acid with chromic acid

Cited by 17 publications

References 23 publications

Promising Biocompatible, Biodegradable, and Inert Polymers for Purification of Wastewater by Simultaneous Removal of Carcinogenic Cr(VI) and Present Toxic Heavy Metal Cations: Reduction of Chromium(VI) by Poly(ethylene glycol) in Aqueous Perchlorate Solutions

Promising Biocompatible, Biodegradable, and Inert Polymers for Purification of Wastewater by Simultaneous Removal of Carcinogenic Cr(VI) and Present Toxic Heavy Metal Cations: Reduction of Chromium(VI) by Poly(ethylene glycol) in Aqueous Perchlorate Solutions

Kinetics of Oxidation of Atropine by K2Cr2O7 in Acidic Aqueous Solutions

Mechanism of oxidation of L-ascorbic acid by the pentaamminechromatocobalt(III) complex ion in aqueous solution

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