Catalysis by zinc ion in the reactions of carcinogenic chromium(VI) with thiols

Perez‐Benito, Joaquin F.; Saiz, Natividad; Amat, E.

doi:10.1016/s1381-1169(97)00284-7

Cited by 12 publications

(13 citation statements)

References 37 publications

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“…In both cases the decrease of the rate as the reaction advanced was faster than expected for a reaction first order in chromate (L-cysteine was in large excess), the deviation from pseudo-first-order kinetics being more pronounced in the air-saturated reaction. This can be interpreted in terms of Scheme 1 [19][20][21][22], where I is the long-lived chromium(VI) thioester intermediate HRSCrO À 3 (HRSH being L-cysteine) [23][24][25], whose formation and decay can be followed at 430 nm (typical lifetime % 10 min). The rates of formation of this intermediate in the argon-saturated and air-saturated reactions were very similar, but its decay was much faster in the argon-saturated reaction (Figure 1, top).…”

Section: Kinetic Behaviormentioning

confidence: 99%

“…This sequence is the opposite of that corresponding to the yield of the intermediates HRSCrO À 3 in the same reactions, and it is coincident with the sequence DL-penicillamine (k 2 ¼ 9:62Â 10 À3 s À1 Þ > L-cysteine ðk 2 ¼ 1:66 Â 10 À3 s À1 Þ > glutathione ðk 2 ¼ 0:80 Â 10 À3 s À1 Þ, corresponding to the rate constants for the redox decay of those intermediates (k 2 in Scheme 1) measured under the same experimental conditions (acetate buffer, ionic strength 0.20 M, pH 5.60, 25.0°C) [22]. This correspondence between the reactivity of HRSCrO À 3 and the yield of CrOO 2+ suggests that the first intermediate is a precursor of the second.…”

Section: Formation Of the Intermediate Croo 2+mentioning

confidence: 99%

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Formation of Superoxochromium(III) by a Novel Mechanism

Perez‐Benito

2006

Transition Met Chem

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The reduction of chromate ion by L-cysteine in near-neutral aqueous solutions was studied by u.v.-vis spectroscopy. The rate constants for the formation, decomposition and redox degradation of a Cr VI thioester intermediate (both in the absence and in the presence of dissolved O 2 ) were determined by the use of a nonlinear least-squares regression to fit the experimental data to a double-exponential integrated rate law. Superoxochromium(III), CrOO 2+ , could be observed as a long-lived intermediate by the use of u.v. difference spectroscopy (peaks at 238 and 292 nm). The effects of several reaction variables on the yield of the intermediate CrOO 2+ were studied. A striking result was that the yield decreased as the concentration of dissolved O 2 increased. In the presence of phosphate buffer, the yield showed a maximum at pH 6.8. Formation of CrOO 2+ was suppressed by the additives Mn 2+ , H 2 O 2 , D-ribose, 2-deoxy-D-ribose and a high concentration of Ce 3+ , whereas a low concentration of the latter enhanced its appearance. A novel mechanism for the formation of CrOO 2+ from Cr VI and L-cysteine (involving the intramolecular formation of an O-O bond) is proposed, and the possible routes for the decay of this intermediate are discussed. This novel mechanism might offer new insights into the redox chemistry of chromate ions.

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Section: Kinetic Behaviormentioning

confidence: 99%

Section: Formation Of the Intermediate Croo 2+mentioning

confidence: 99%

Formation of Superoxochromium(III) by a Novel Mechanism

Perez‐Benito

2006

Transition Met Chem

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“…The former is highly toxic and carcinogenic to human and animals, while the latter is generally non-toxic [4] [5] [6]. Conse-gents including hydrogen sulfide [7], divalent iron [8] [9], Fe(II)-bearing minerals [5] [10], thios and thiols [11] [12], etc. Recently, zero-valent iron (Fe 0 ) has been tested for the remediation of polluted waters, and it is established that halogenated hydrocarbons such as nitro- [13] [14], and chloro-compounds [15], toxic metals nitrate and arsenate [16] [17] [18] [19] [20] are effectively transformed by the Fe 0 to relatively more benign products.…”

Section: Introductionmentioning

confidence: 99%

Pulsed Electrochemical Deposited Nano-Iron for Water Treatment

Fazakas¹,

Zsuzsanna²,

Bak³

et al. 2017

AJAC

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The application of nanotechnology in drinking water treatment and pollution cleanup is promising, as demonstrated by a number of field-based (pilot and full scale) and bench scale studies. In recent years, the use of zero-valent iron (ZVI) for the treatment of toxic contaminants in groundwater and wastewater has received wide attention and encouraging treatment efficiencies have been documented. In this review, nanoscale iron was prepared by pulse electrodeposition of nano iron by chemical reduction of iron chloride and iron sulfate. Our research focuses on iron nanoparticles preparation and its use for aqueous Cr(VI) reduction. The Cr(VI) reduction by the nFe 0 prepared by electrochemical and blasting method at neutral pH were carried. The results show that blasting-nFe 0 show lower reaction than the electrochemical-nFe 0 . It is because the blasting-nFe 0 surface contains more Fe 2 O 3 than the other one.

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“…This requires an increased understanding of how metals are absorbed, transported, and stored in vivo and of how chelating agents can arrest these processes and promote excretion of the toxic metal [8]. Therefore, the studies on the interaction of metal ions with amino acids increased in the recent years [9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…Although investigations on the interactions of Cr(VI) with thiol compounds have been extensively reported [9,10,[18][19][20][21], no electrochemical and spectroscopic studies dealing with the fotocatalytic effect of UV light on the interaction of Cr(VI) with cysteine have appeared in the literature. Therefore, in the present work, the role of UV irradiation in the reduction of Cr(VI) with cysteine has been investigated with cyclic voltammetry and electronic spectroscopy techniques.…”

Section: Introductionmentioning

confidence: 99%