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

González, Juan Carlos; Garcı́a, Silvia; Mamana, Nadia; Sala, Luis F.; Signorella, Sandra

doi:10.1016/j.inoche.2006.02.002

Cited by 13 publications

(7 citation statements)

References 29 publications

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“…The intensity ratio between the absorption bands at 245 and 290 nm was 2.2, which conrmed . 18,55,56,63 As occurred with other substrates studied previously, 18,[25][26][27]37 the monotonic growth at 290 nm was found to follow rst-order kinetics (Fig. 6B).…”

Section: Rate Studiessupporting

confidence: 82%

Quinic acid and hypervalent chromium: a spectroscopic and kinetic study

et al. 2018

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Section: Rate Studiessupporting

confidence: 82%

Quinic acid and hypervalent chromium: a spectroscopic and kinetic study

et al. 2018

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“…In both the Watanabe-Westheimer mechanism [37] (i.e. Path I) and the Perez-Bennito mechanism [1,38,39] (i.e. Path III), the title organic substrate acts in all steps as a 2e reductant, while it acts both as a 2e-reductant and 1e-reductant in the Rocek mechanism [40] (i.e.…”

Section: Catalysed Pathmentioning

confidence: 99%

“…Previously, the Rocek mechanism [40] was accepted widely in explaining the Cr(VI) oxidation of different organic substrates and the Perez-Bennito mechanism [1,38,39] was discarded because of the instability of Cr(II). But recently, it has been proved [1,38,39] that for the oxidation of different 2e-organic reductants, Cr(II) is produced from Cr(IV) through hydride transfer. Thus, the carbocationic centre generated is responsible for acrylonitrile polymerization [41].…”

Section: Catalysed Pathmentioning

confidence: 99%

“…To understand the mechanistic aspects of reduction of Cr(VI) to Cr(III), several kinetic studies of chromic acid oxidation of different types of organic substrates have been carried out by different workers [1][2][3]. Kinetic studies of oxidation of different types of organic substrate by halochromate have also been investigated by different workers [4,5] to explore the effect of the substituent on the redox activity of Cr(VI).…”

Section: Introductionmentioning

confidence: 99%

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Kinetics and Mechanism of Oxidation of D-Galactose by Chromium(VI) in Presence of 2,2’-Bipyridine Catalyst in Aqueous Micellar Media

Bayen¹,

K.²

2009

TOCATJ

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In aqueous H 2 SO 4 media, the chromic acid oxidation of D-galactose in the presence and absence of 2,2´bipyridine (bpy) has been carried out under the conditions, [D-galactose] T >> [Cr(VI)] T at different temperatures. The monomeric species of Cr (VI) has been found to be kinetically active in the absence of bpy whereas in the bpy-catalysed path, the Cr(VI)-bpy complex has been suggested as the active oxidant. In the bpy-catalysed path, Cr(VI)-bpy complex receives a nucleophilic attack by the substrate to form a ternary complex, which subsequently experiences a redox decomposition (through 2e transfer) at the rate-determining step leading to the product lactone and Cr(IV)-bpy complex. Then the Cr(IV)-bpy complex participates in faster steps in further oxidation of D-galactose and ultimately it is converted into Cr(III)-bpy complex. In the uncatalysed path, Cr(VI)-substrate ester experiences acid catalysed redox decomposition (2e-transfer) at the rate determining step. The uncatalysed path shows second order dependence on [H + ] while the bpycatalysed path shows a first order dependence on [H + ]. Both the uncatalysed path and bpy-catalysed path show the first order dependence on both [D-galactose] T and [Cr(VI)] T. The bpy-catalysed path is first order in [bpy] T. These observations remain unaltered in the presence of externally added surfactants. Effect of the surfactants like N-cetylpyridinium chloride (CPC, a cationic surfactant) and sodium dodecyl sulfate (SDS, an anionic surfactant), on both the uncatalysed and bpycatalysed paths has been studied. CPC inhibits both the uncatalysed and bpy-catalysed path, while SDS accelerates the reactions. In the catalysed path, cationic Cr(VI)-bpy complex is the reactive species which is attracted by the anionic micellar head groups of SDS but repelled by the cationic micellar head groups of CPC. The neutral substrate is accumulated in the Stern layer of both types of micelles. Thus the observed micellar effects have been explained by considering the hydrophobic and electrostatic interactions between the reactants and surfactants in terms of the proposed mechanism.

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“…Chromates are important agents for the oxidation of organic species, but questions about the active mechanisms remain. − Many reaction mechanisms have been suggested to describe the chromate-induced oxidation of alcohols including the formation of cyclic chromate esters and various electron-transfer pathways . Chromate esters have been of interest since they were first observed in the late 1800s, and much work has been done to improve our understanding of their chemistry in solution.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopy and Photochemistry of Sodium Chromate Ester Cluster Ions

Kaufman

Weber

2013

J. Phys. Chem. A

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In the present study, we investigate the spectroscopy and photochemical behavior of chromate ester cluster ions in vacuo in the visible and near-UV. Chromate ester cluster ions Na(n)[CrO3(OCH3)](n+1)(-) (n = 1, 2) are generated by electrospray ionization of sodium dichromate in water and methanol. Upon irradiation with photon energies between 2 and 5.6 eV, dissociation occurs. The photodissociation spectra of these ions are very similar to the UV/vis absorption spectra of the sample solution with solvatochromic shifts less than 0.1 eV. The electronic excitations in this photon energy range are assigned to ligand-to-metal charge transfer from the oxygen ligands to the chromium within the chromate ester. Fragment channels corresponding to intracluster reactions involving reduction of the metal centers as well as evaporative processes leading to the loss of a neutral Na[CrO3(OCH3)] salt unit are observed. The results are discussed in the framework of organometallic redox mechanisms and density functional theory.

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

Cited by 13 publications

References 29 publications

Quinic acid and hypervalent chromium: a spectroscopic and kinetic study

Quinic acid and hypervalent chromium: a spectroscopic and kinetic study

Kinetics and Mechanism of Oxidation of D-Galactose by Chromium(VI) in Presence of 2,2’-Bipyridine Catalyst in Aqueous Micellar Media

Spectroscopy and Photochemistry of Sodium Chromate Ester Cluster Ions

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