Kinetics and mechanism of the reduction of CrVI and CrV by d-lactobionic acid

Roldán, Viviana; Santoro, Mabel; González, Juan Carlos; Salas-Peregrín, J.M.; Signorella, Sandra; Sala, Luis F.

doi:10.1016/j.jinorgbio.2003.11.005

Cited by 10 publications

(12 citation statements)

References 41 publications

(58 reference statements)

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“…2b and Table 1. The presence of the weak 53 Cr hyperfine peaks with A iso = 16.9(3) × 10 −4 cm −1 , Table 1, demonstrated that each of these components originated from Cr. At pH 7.5 (Hepes buffer) only a very weak EPR signal was observed for oxo-Cr V -Glucar, which may point to instability of complexes at this pH value.…”

Section: Resultsmentioning

confidence: 94%

“…This spectrum consisted of a major signal, 86%, (from 52 Cr) centered at g iso = 1.9784, flanked by a weak quartet from the 53 Cr isotope (I = 3/2, natural abundance 9.5%), 53 CrA iso = 16.7 (2) × 10 −4 cm −1 , Fig. 1.…”

Section: Resultsmentioning

confidence: 98%

“…Assignment of the probable structures of the oxo-Cr V species in solution have, therefore, been made on the basis of the isotropic EPR parameters g iso , A iso and 1 Ha iso together with any proton shfs. An empirical relationship between the nature and number of donor groups and the EPR spectral parameters of oxo-Cr V complexes has been established, and five-coordinated oxo-Cr V species have higher g iso and lower 53 CrA iso values than the corresponding six-coordinated species. 20,21 It is known that the five-membered oxo-Cr V chelates are more stable than the six-membered ones 21,44,45 and, in addition, Glucar is well suited for stabilization of five-membered oxo-Cr V chelates since it has α-hydroxycarboxylate and vic-diolate sites for potential chelation.…”

Section: Discussionmentioning

confidence: 99%

“…a t = triplet. 1 Ha iso and 53 CrA iso parameters are in 10 −4 cm −1 . Isotropic spectra were simulated using the WinSim program.…”

Section: Detection Of Cr VI Estersmentioning

confidence: 99%

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Redox and complexation chemistry of the CrVI/CrV-d-glucaric acid system

et al. 2014

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When an excess of uronic acid over Cr(VI) is used, the oxidation of D-glucaric acid (Glucar) by Cr(VI) yields D-arabinaric acid, CO2 and Cr(III)-Glucar complex as final redox products. The redox reaction involves the formation of intermediate Cr(IV) and Cr(V) species. The reaction rate increases with [H(+)] and [substrate]. The experimental results indicated that Cr(IV) and Cr(V) are very reactive intermediates since their disappearance rates are much faster than Cr(VI). Cr(IV) and Cr(V) intermediates are involved in fast steps and do not accumulate in the redox reaction of the mixture Cr(VI)-Glucar. Kinetic studies show that the redox reaction between Glucar and Cr(VI) proceeds through a mechanism combining one- and two-electron pathways: Cr(VI) → Cr(IV) → Cr(II) and Cr(VI) → Cr(IV) → Cr(III). After the redox reaction, results show a slow hydrolysis of the Cr(III)-Glucar complex into [Cr(OH2)6](3+). The proposed mechanism is supported by the observation of free radicals, CrO2(2+) (superoxo-Cr(III) ion) and oxo-Cr(V)-Glucar species as reaction intermediates. The continuous-wave electron paramagnetic resonance, CW-EPR, spectra show that five-coordinate oxo-Cr(V) bischelates are formed at pH ≤ 4 with the aldaric acid bound to oxo-Cr(V) through the carboxylate and the α-OH group. A different oxo-Cr(V) species with Glucar was detected at pH 6.0. The high g(iso) value for the last species suggests a mixed coordination species, a five-coordinated oxo-Cr(V) bischelate with one molecule of Glucar acting as a bi-dentate ligand, using the 2-hydroxycarboxylate group, and a second molecule of Glucar with any vic-diolate sites. At pH 7.5 only a very weak EPR signal was observed, which may point to instability of these complexes. This behaviour contrasts with oxo-Cr(V)-uronic species, and must thus be related to the Glucar acyclic structure. In vitro, our studies on the chemistry of oxo-Cr(V)-Glucar complexes can provide information on the nature of the species that are likely to be stabilized in vivo.

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

“…a t = triplet. 1 Ha iso and 53 CrA iso parameters are in 10 −4 cm −1 . Isotropic spectra were simulated using the WinSim program.…”

Section: Detection Of Cr VI Estersmentioning

confidence: 99%

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Redox and complexation chemistry of the CrVI/CrV-d-glucaric acid system

et al. 2014

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“…Cr IV ! Cr III pathways was proposed for the oxidation of D-lactobionic [21] and D-galacturonic [22] acids by HCrO À 4 . In view of these results, we decided to check the possibility that the combination of one-and two-electron pathways for the reduction of intermediate Cr IV by the organic substrate could be generalized.…”

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confidence: 99%

Evidence for the involvement of CrII and free radicals as intermediates in the reduction of by saccharides, alcohols and hydroxyacids

González

Garcı́a

Mamana

et al. 2006

Inorganic Chemistry Communications

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Kinetics and mechanism of oxidation of apple pectin by Cr^VI in aqueous acid medium

Bellú

González

Garcı́a

et al. 2008

J of Physical Organic Chem

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Selective oxidation of galacturonic acid residues of apple pectin by CrVI affords CO2/HCO2H, oxidized pectin, and CrIII as final redox products. The reaction shows first‐order kinetics in [pectin], [CrVI], and [H+], at fixed ionic strength and temperature. Kinetic studies show that the redox reaction proceeds through a mechanism combining CrVI → CrIV → CrII and CrVI → CrIV → CrIII pathways. The mechanism is supported by the observation of free radicals, CrO (the formation of which implies involvement of CrII and CrIV) and CrV (formed in monoelectronic redox processes) as reaction intermediates. The reduction of CrIV and CrV by pectin was independently studied and found to occur more than 103 times faster than pectin + CrVI reaction, in acid medium. At pH 3–5, apple pectin + CrVI redox reaction is slow, oxo‐chromate(V)–pectin species stabilize and remain in solution during several hours. The present results show that these abundant and ubiquitous components of the cell walls of all land plants are able to reduce CrIV–VI or stabilize high‐valent chromium depending on pH. Copyright © 2008 John Wiley & Sons, Ltd.

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Kinetics and mechanism of the reduction of CrVI and CrV by d-lactobionic acid

Cited by 10 publications

References 41 publications

Redox and complexation chemistry of the CrVI/CrV-d-glucaric acid system

Redox and complexation chemistry of the CrVI/CrV-d-glucaric acid system

Evidence for the involvement of CrII and free radicals as intermediates in the reduction of by saccharides, alcohols and hydroxyacids

Kinetics and mechanism of oxidation of apple pectin by Cr^VI in aqueous acid medium

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Kinetics and mechanism of the reduction of CrVI and CrV by d-lactobionic acid

Cited by 10 publications

References 41 publications

Redox and complexation chemistry of the CrVI/CrV-d-glucaric acid system

Redox and complexation chemistry of the CrVI/CrV-d-glucaric acid system

Evidence for the involvement of CrII and free radicals as intermediates in the reduction of by saccharides, alcohols and hydroxyacids

Kinetics and mechanism of oxidation of apple pectin by CrVI in aqueous acid medium

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Kinetics and mechanism of oxidation of apple pectin by Cr^VI in aqueous acid medium