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001-es BibID:BIBFORM062911
Első szerző:Dóka Éva (vegyész)
Cím:Kinetics of the autoxidation of sulfur(iv) co-catalyzed by peroxodisulfate and silver(i) ions / Éva Dóka, Gábor Lente, István Fábián
Dátum:2014
ISSN:1477-9226
Megjegyzések:The kinetics and mechanism of the reaction between dissolved oxygen and sulfur(IV) was studied inaqueous acidic medium using co-catalysts peroxodisulfate and silver(I) ions. The presence of both catalystswas required to observe measurable rates in the studied process. The reaction rate was determinedthrough following the UV-absorption of hydrated sulfur dioxide, and the trends were determined as afunction of pH, reactant and catalyst concentrations. Individual kinetic curves under conditions where dissolvedoxygen was the limiting reagent were close to zeroth-order. A chain mechanism with four chaincarriers, sulfite, sulfate, peroxomonosulfate ion radical and silver(II) ion, is proposed to interpret all thekinetic and stoichiometric findings, and an explicit formula was obtained for the rate law. The role of theco-catalysts is to produce chain carriers, whereas silver(I) and silver(II) ions also participate in chain propagationsteps. Further supporting evidence for the proposed mechanism was gained in laser flash photolysisstudies, which showed that sulfate ion radical reacts quite rapidly with silver(I) ion.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
kén(IV)
autooxidáció
katalízis
Megjelenés:Dalton Transactions. - 43 : 25 (2014), p. 9596-9603. -
További szerzők:Lente Gábor (1973-) (vegyész) Fábián István (1956-) (vegyész)
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2.

001-es BibID:BIBFORM062914
Első szerző:Kalmár József (vegyész)
Cím:Aqueous photochemical reactions of chloride, bromide, and iodide ions in a diode-array spectrophotometer. Autoinhibition in the photolysis of iodide ions / József Kalmár, Éva Dóka, Gábor Lente, István Fábián
Dátum:2014
ISSN:1477-9226
Megjegyzések:The aqueous photoreactions of three halide ions (chloride, bromide and iodide) were studied using adiode array spectrophotometer to drive and detect the process at the same time. The concentration andpH dependences of the halogen formation rates were studied in detail. The experimental data were interpretedby improving earlier models where the cage complex of a halogen atom and an electron has acentral role. The triiodide ion was shown to exert a strong inhibiting effect on the reaction sequenceleading to its own formation. An assumed chemical reaction between the triiodide ion and the cagecomplex interpreted the strong autoinhibition effect. It is shown that there is a real danger of unwantedinterference from the photoreactions of halide ions when halide salts are used as supporting electrolytesin spectrophotometric experiments using a relatively high intensity UV light source.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
iodide
photochemistry
autoinhibition
Megjelenés:Dalton Transactions. - 43 : 12 (2014), p. 4862-4870. -
További szerzők:Dóka Éva (1988-) (vegyész) Lente Gábor (1973-) (vegyész) Fábián István (1956-) (vegyész)
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3.

001-es BibID:BIBFORM062162
035-os BibID:(WoS)000351483700013 (Scopus)84925484963
Első szerző:Vasas Anita (környezetkutató)
Cím:Kinetic and thermodynamic studies on the disulfide-bond reducing potential of hydrogen sulfide / Anita Vasas, Éva Dóka, István Fábián, Péter Nagy
Dátum:2015
ISSN:1089-8603
Megjegyzések:The significance of persulfide species in hydrogen sulfide biology is increasingly recognized. However,the molecular mechanisms of their formation remain largely elusive. The obvious pathway of the reduction of biologically abundant disulfide moieties by sulfide was challenged on both thermodynamicand kinetic grounds. Using DTNB (5,5·-dithiobis-(2-nitrobenzoic acid), also known as Ellman's reagent)as a model disulfide we conducted a comprehensive kinetic study for its reaction with sulfide. The bimolecular reaction is relatively fast with a second-order rate constant of 889 ? 12 M?1s?1 at pH = 7.4. pHdependence of the rate law revealed that the reaction proceeds via the bisulfide anion species with aninitial nucleophilic thiol-disulfide exchange reaction to give 5-thio-2-nitrobenzoic acid (TNB) and TNBpersulfide with a pH independent second-order rate constant of 1090 ? 12 M?1s?1. However, kinetic studiesand stoichiometric analyses in a wide range of reactant ratios together with kinetic simulations revealed that it is a multistep process that proceeds via kinetically driven, practically irreversible reactionsalong the disulfide ? persulfide ? inorganic polysulfides axis. The kinetic model postulated here, whichis fully consistent with the experimental data, suggests that the TNB-persulfide is further reduced bysulfide with a second-order rate constant in the range of 5 ? 103 ? 5 ? 104 M?1s?1 at pH 7.4 and eventually yields inorganic polysulfides and TNB. The reactions of cystine and GSSG with sulfide were foundto be significantly slower and to occur via more complicated reaction schemes. 1H NMR studies suggestthat these reactions also generate Cys-persulfide and inorganic polysulfide species, but in contrast withDTNB, in consecutive equilibrium processes that are sensitive to changes in the reactant and productratios. Collectively, our results demonstrate that the reaction of disulfides with sulfide is a highly systemspecific process from both thermodynamic and kinetic aspects, which together with the considerablesteady-state concentrations of the reactants in biological systems signifies physiological relevance.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Hydrogen sulfide
Disulfide reduction
Persulfide
Kinetics and mechanisms
Speciation
Megjelenés:Nitric Oxide-Biology And Chemistry. - 46 (2015), p. 93-101. -
További szerzők:Dóka Éva (1988-) (vegyész) Fábián István (1956-) (vegyész) Nagy Péter (1976-) (vegyész)
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