Oxidation of uranium(IV) by chromium(VI) and the induced oxidation of iodide ions

Espenson, James H.; Wang, Robert T.

doi:10.1021/ic50111a007

Cited by 15 publications

(6 citation statements)

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“…Although, chromic acid has been extensively used for oxidation of inorganic [7,8,[11][12][13][14][15] and organic compounds [16][17][18][19][20][21][22][23][24], a little attention has been focused on the oxidation of amino acids by this oxidant [17,24]. This fact may be attributed to the complexity resulting from the existence of various species of chromium(VI) in acidic medium as well as the instability of Cr V and Cr IV oxidation states through the reduction of chromium ion from hexavalent to trivalent state.…”

Section: Introductionmentioning

confidence: 99%

Kinetics and mechanistic approach to the chromic acid oxidation of l-tryptophan with a spectral detection of chromium(III) product

Fawzy

Ashour

Musleh

et al. 2016

Journal of Saudi Chemical Society

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The kinetics of chromic acid oxidation of L-tryptophan in H 2 SO 4 medium at a constant ionic strength of 0.6 mol dm À3 and at 25°C have been investigated spectrophotometrically. The reaction exhibits a 3:2 stoichiometry (tryptophan:chromic acid). The reaction shows a first order dependence on [chromic acid], a fractional-first order dependence on [tryptophan] and fractionalsecond order dependence on [acid]. Increasing ionic strength and dielectric constant had no significant effect on the oxidation rate. The final oxidation products of tryptophan were identified as the corresponding aldehyde (indole-3-acetaldehyde), ammonium ion and carbon dioxide. A spectral evidence for the formation of chromium(III) product was obtained. The experimental results suggest formation of an intermediate complex between the protonated tryptophan and chromic acid which decomposes in the rate-determining step to yield the products. The mechanism of such reaction has been proposed. The thermodynamic parameters with respect to the first step of the suggested mechanism were evaluated and discussed. ª 2014 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

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Section: Introductionmentioning

confidence: 99%

Kinetics and mechanistic approach to the chromic acid oxidation of l-tryptophan with a spectral detection of chromium(III) product

Fawzy

Ashour

Musleh

et al. 2016

Journal of Saudi Chemical Society

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“…It has been demonstrated that the oxidation of uranium(IV) by multiequivalent oxidants such as MnO 4 – as an oxyanion and VO 2 + as an oxycation occurred by successive one-electron transfer mechanism in a sequence with the formation of ion-pairs, but the oxidation of U IV by oxyanion chromate, CrO 4 2– , was proceeding by a simultaneous two-electron changes in a single step. The transfer of one and/or two oxygen atoms from the oxidant to form single or doubly bridged transition states between the reactants was postulated in those redox reactions.…”

Section: Introductionmentioning

confidence: 99%

A Mechanistic Approach to the Kinetics of Oxidation of Uranium(IV) by Hexachloroplatinate(IV) in Aqueous Perchlorate Solutions. Evidence of the Formation of a Binuclear Intermediate Complex

Hassan

2011

J. Phys. Chem. A

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The kinetics of hexachloroplatinate(IV) oxidation of uranium(IV) ion in aqueous perchloric acid solutions at a constant ionic strength of 1.0 mol dm(-3) has been investigated using the stopped-flow and conventional spectrophotometric techniques. The oxidation reaction was found to proceed through two distinct stages. The initial stage was found to be relatively fast corresponding to the formation of [(H(2)O)(n)U(IV)·Cl(6)Pt(IV)](2+) binuclear intermediate complex (with the rate constant k(1) = 1.75 × 10(4) dm(3) mol(-1)s(-1), k(-1) = 6.8 s(-1), and the formation constant K = 2.6 × 10(3) dm(3) mol(-1) at [H(+)] = 1.0 mol dm(-3) and 25 °C for binuclear formation). This stage was followed by a much slower stage corresponding to the transfer of two electrons from U(IV) to Pt(IV) in the rate-determining step (with the rate constant k = 5.32 × 10(-5) s(-1) at [H(+)] = 1.0 mol dm(-3) and 25 °C). The reaction stoichiometry was found to depend on the molar ratio of the reactants concentration. The experimental results indicated the decrease of the observed first-order rate constants with increasing the [H(+)] for the decomposition of the binuclear intermediate complex through the slow-second stage, whereas no change was observed with respect to the rate of formation of the binuclear complex at the initial rapid part. A tentative reaction mechanism consistent with the kinetic results is discussed.

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“…43 Moreover, the establishment of Cr III was emphasized by the rebate in the reactions’ rates after addition of Mn II ions to the reaction sets. 26 , 33 …”

Section: Resultsmentioning

confidence: 99%

“…The byproducts were identified as NH 4 + and CO 2 as described elsewhere . Moreover, the establishment of Cr III was emphasized by the rebate in the reactions’ rates after addition of Mn II ions to the reaction sets. , …”

Section: Resultsmentioning

confidence: 99%

“…Consequently, various reductants are used to transform toxic chromium(VI) compounds into safe chromium(III) compounds. A literature survey illuminated that a variety of studies were published on chromic acid oxidation of distinctive inorganic , and organic − compounds, whereas there are not much reports about oxidation by chromium trioxide. − …”

Section: Introductionmentioning

confidence: 99%

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Unprecedented Treatment Strategy of Aquatic Environments: Oxidative Degradation of Penicillin G by Chromium Trioxide in Acidic Media and the Impact of Metal Ion Catalysts: Kinetics and Mechanistic Insights

Fawzy

Toghan

2020

ACS Omega

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Degradation kinetics and pathways of the antibiotic penicillin G (Pen) have been examined via oxidation by chromium trioxide (Cr VI ) in aqueous sulfuric and perchloric acid media. The oxidation reactions were monitored by spectrophotometry at 298 K. In both acidic media, penicillin G oxidation was set to proceed through acid catalysis. The stoichiometry of the reactions designated that 3 moles of Pen required 2 moles of Cr VI . The kinetics of Pen oxidation in both acids was of the first order with regard to [Cr VI ] and less-than unity order with regard to [Pen] and [H + ] in their variation. The rates of reactions displayed negligible impacts upon altering ionic strengths or dielectric constants of the reaction media. There was no intrusion of free radicals throughout the redox reactions. Addition of low concentrations of Ni 2+ , Cu 2+ , and Zn 2+ ions enhanced the oxidation rates, while addition of Cr 3+ as a described product did not noteworthily alter the rates. Under comparable investigational circumstances, the oxidation rates in HClO 4 were almost 2-fold greater than in H 2 SO 4 . The oxidation products of penicillin G were identified by spectral analysis and spot tests as phenyl acetic acid, 2-formyl-5,5-dimethyl-thiazolidine-4-carboxlate ion, ammonium ion, and carbon dioxide. Reliance of reaction rates on temperature has been explored, and the activation and thermodynamic parameters were estimated and debated. In view of the noted reactions’ orders and products’ identification, a plausible mechanism for the oxidation reactions was suggested. The derived rate law was set to be in accordance with the acquired results. This study offers an unprecedented simple and low-cost treatment method for removal or degradation of certain pollutants for protecting the environment and human health.

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Oxidation of uranium(IV) by chromium(VI) and the induced oxidation of iodide ions

Cited by 15 publications

References 1 publication

Kinetics and mechanistic approach to the chromic acid oxidation of l-tryptophan with a spectral detection of chromium(III) product

Kinetics and mechanistic approach to the chromic acid oxidation of l-tryptophan with a spectral detection of chromium(III) product

A Mechanistic Approach to the Kinetics of Oxidation of Uranium(IV) by Hexachloroplatinate(IV) in Aqueous Perchlorate Solutions. Evidence of the Formation of a Binuclear Intermediate Complex

Unprecedented Treatment Strategy of Aquatic Environments: Oxidative Degradation of Penicillin G by Chromium Trioxide in Acidic Media and the Impact of Metal Ion Catalysts: Kinetics and Mechanistic Insights

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