Separation of americium(III) from lanthanides(III) by nanofiltration-complexation in aqueous medium

The separation of Am(III) from a mixture of lanthanides(III) was performed in aqueous medium by nanofiltration combined with a complexation step using a DTPA derivative as selective complexing agent.     

Solvent extraction of lanthanum(III) and cerium(III) with dialkyldithiophosphoric acids. Separation from thorium(IV)

The extraction of lanthanum(III) and cerium(III) with dialkyldithiophosphoric acids, Hdtp, into different polar and nonpolar solvents (cyclohexane, benzene, carbon tetrachloride, chloroform, diethyl ether, dibutyl ether, n-butanol and cyclohexanone) from aqueous solutions containing perchlorate, nitrate and chloride anions has been investigated. The effect of various factors, such as nature of the solvent, pH, metal concentration and foreign anions present in the aqueous phase was investigated in order to establish the mechanism of extraction process. The data obtained suggest an ion-exchange mechanism. The anions present in the aqueous phase do not participate in the extraction process and do not influence significantly the magnitude of the extraction ratios either. The extracted species in the organic phase is a 12 complex of lanthanide with Hdtp. The extraction efficiency (E%) is calculated and the possibility of Th-rare earths separation is discussed.     

Spectral and mechanistic investigations of ruthenium(III) catalyzed oxidation of atenolol by diperiodatocuprate(III) in aqueous alkaline medium

The kinetics of ruthenium(III) catalyzed oxidation of atenolol by diperiodatocuprate(III) in aqueous alkaline medium at a constant ionic strength of I = 0.10 M has been studied spectrophotometrically at 27°C. The reaction between diperiodatocuprate(III) and atenolol in alkaline medium in presence of ruthenium(III) exhibits 2: 1 stoichiometry (atenolol: diperiodatocuprate(III)). The main products were identified by spot test, IR, NMR, and LC-MS. The reaction is of first order in DPC concentrations and has less than unit order in both ATN and alkali concentrations. The order in ruthenium(III) was unity. Intervention of free radicals was observed in the reaction. Increase in periodate concentration decreases the rate. The oxidation reaction in alkaline medium has been shown to proceed via a ruthenium(III)-atenolol complex, which reacts with monoperiodatocuprate(III) in a rate determining step followed by other fast steps to give the products. Probable mechanism is proposed and discussed. The activation parameters with respect to the slow step of the mechanism and thermodynamic quantities were determined and discussed.     

Ruthenium(III) catalyzed oxidation of hexacyanoferrate(II) by periodate in aqueous alkaline medium

Ruthenium(III) catalyzed oxidation of hexacyanoferrate(II) by periodate in alkaline medium is assumed to occurvia substrate-catalyst complex formation followed by the interaction of oxidant and complex in the rate-limiting stage and yield the products with regeneration of catalyst in the subsequent fast step. The reaction exhibits fractional order in hexacyanoferrate(II) and first-order unity each in oxidant and catalyst. The reaction constants involved in the mechanism are derived.     

Potentiometric studies of indium(III) azide complexes in aqueous medium

The stability constants of indium-azide complexes were determined by the potentiometric method (glass electrode). The effect monitored was the change in pH of a solution of azide and hydrazoic acid (N(-)(3)/HN(3)) when indium(III) cations were added. The azide concentration was varied from close to zero to 90mM, the ionic strength being kept at 2.000 M with sodium perchlorate and the temperature at 25.0 degrees . Evaluation of experimental data showed only mononuclear species, and the global constants found were beta(1) = (2.0 +/- 0.1) x 10(3), beta(2) = (7 +/- 2) x 10(5), beta(3) = (5 +/- 1) x 10(7) and beta(4) = (7 +/- 3) x 10(8).     

Mechanistic investigations of ruthenium(III) catalyzed oxidation of pentoxifylline by copper(III) periodate complex in aqueous alkaline medium

Abstract  

The kinetics of the oxidation of ruthenium(III)-catalyzed oxidation of pentoxifylline (PTX) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.30 mol dm⁻³ was studied spectrophotometrically. The reaction between PTX and DPC in alkaline medium in the presence of Ru(III) exhibits 1:2 stoichiometry (PTX:DPC). The reaction was of first order in DPC, less than the unit order in [PTX] and [OH⁻] and negative fractional order in [IO₄ ⁻]. The order in [Ru(III)] was unity. Intervention of free radicals was observed in the reaction. The main products were identified by TLC and spectral studies including LC-MS. The oxidation reaction in alkaline medium has been shown to proceed via a Ru(III)-PTX complex, which reacts with monoperiodatocuprate(III) to decompose in a rate determining step followed by a fast step to give the products. The reaction constants involved in different steps of the mechanism were calculated. The activation parameters with respect to the slow step of the mechanism were computed and discussed, and thermodynamic quantities were also determined. The active species of catalyst and oxidant have been identified.     

Oxidation of L-lysine by diperiodatocuprate (III) in aqueous alkaline medium by the stopped flow technique

The kinetics of oxidation of L-lysine by diperiodatocuprate (III) (DPC) in alkaline medium at a constant ionic strength of 0.15 mol/dm³ was studied spectrophotometrically. The reaction between DPC and L-lysine in an alkaline medium had a 1: 2 stoichiometry (L-lysine: DPC). The reaction was first order in [DPC] and less than first order in [L-lysine] and [alkali]. The addition of periodate had no effect on the rate of the reaction. The intervention of free radicals was observed in the reaction. The oxidation reaction in alkaline medium was shown to proceed via a DPC-L-lysine complex. The main products were identified by spot test and spectral studies. The reaction constants involved in different steps of the mechanism were calculated. The activation parameters with respect to the slow step of the mechanism were computed and discussed, and thermodynamic values were also determined. The article is published in the original.     

Kinetic and mechanistic studies of the iridium(III) catalyzed oxidation of sulphanilic acid by diperiodatocuprate(III) in aqueous alkaline medium

The effect of La₂O₃, K₂O and Li₂O on the properties and catalytic performance of silica-supported nickel catalysts for the hydrogenation of m-dinitrobenzene was investigated. The catalysts promoted with La₂O₃, Li₂O and K₂O showed better catalytic performance than the catalyst without promotion, especially the ones co-promoted with La₂O₃ and K₂O or Li₂O.     

Chloride and iodide mediated oxidation of antimony(III) by cerium(IV) in aqueous sulphuric acid medium

The micro amounts of iodide (10⁻⁷) (mol dm⁻³) and chloride (10⁻²) (mol dm⁻³) mediated oxidation of antimony(III) by cerium(IV) in an aqueous sulphuric acid medium have been studied spectrophotometrically at 25 °C and μ = 3.10 mol dm⁻³. The stoichiometry is 1:2 in chloride and iodide mediated reactions. i.e. one mole of antimony(III) requires two moles of cerium(IV). In the case of chloride mediated reaction, the reaction was first order in cerium(IV) and halide concentrations, whereas in the case of iodide mediated reaction the order with respect to [cerium(IV)] was unity and with respect to iodide concentrations was more than unity (ca. 1.4). In both chloride and iodide mediated reactions the order with respect to antimony(III) concentrations was less than unity. Increase in sulphuric acid concentration increased the rate. The order with respect to H⁺ ion concentration was less than unity. Added products, cerium(III) and antimony(V) did not have any significant effect on the reaction rate. The active species of oxidant was understood to be , whereas that of reductant as SbCl₃ in the case of chloride and SbI²⁺ in case of iodide mediated reactions. The possible reaction mechanisms were proposed and the activation parameters were determined and discussed.     

Ruthenium(III) catalyzed oxidation of sulfanilic acid by diperiodatocuprate(III) in aqueous alkaline medium. A kinetic and mechanistic approach

The kinetics of ruthenium(III) catalyzed oxidation of sulfanilic acid by diperiodatocuprate(III) (DPC) in alkaline medium at a constant ionic strength of (0.50 mol dm⁻³) has been studied spectrophoto-metrically. The reaction between sulfanilic acid and DPC in alkaline medium exhibits 1: 4 stoichiometry (sulfanilic acid: DPC). The reaction is first order with respect to [DPC] and [Ru^III] and has less than unit order both in [sulfanilic acid] and [alkali]. The active species of catalyst and oxidant have been identified. Intervention of free radicals was observed in the reaction. The main products were identified by spot test and IR. Probable mechanism is proposed and discussed. The reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to the slow step of the mechanism are computed and discussed. Thermodynamic quantities are also determined.     

Ruthenium (III) catalysed and uncatalysed oxidation of torsemide by hexacyanoferrate (III) in aqueous alkaline medium: A kinetic comparative approach

The kinetics approach of oxidation of torsemide (TOR) by hexacyanoferrate (III) [HCF (III)] has been identified spectrophotometrically at 420 ​nm in the alkaline medium in the presence and absence of catalyst ruthenium (III) at 25 ​°C, by keeping ionic strength (1 ​× ​10⁻² ​mol ​dm⁻³) constant. The reaction exhibits at the stoichiometry ratio 1:2 of TOR and HCF (III), for uncatalysed and catalysed reactions. In the absence and presence of the catalyst, the order of the reactions obtained for TOR and HCF (III) was unity. However, the rate of the reactions enhanced by the increase in the concentration of catalyst, as well as the rate increases with an increase in alkaline concentration. The activation parameters for the reaction at the slow step were identified, and the effect of temperature on the rate of the reaction was analysed. A suitable mechanism has been demonstrated by considering the obtained results. The derived rate laws are reliable with analysed experimental kinetics.     

Thermodynamic quantities for the oxidation of ranitidine by diperiodatocuprate(III) in aqueous alkaline medium

The kinetics of oxidation of the anti-ulcer drug, ranitidine hydrochloride (RNH) by diperiodatocuprate(III) (DPC) in alkaline medium was studied spectrophotometrically. The reaction exhibits 1:2 stoichiometry (ranitidine:DPC). The reaction is of first order in [DPC] and has less than unit order in [RNH] and negative fractional order in [alkali]. The involvement of free radicals was observed in the reaction. The oxidation has been found to proceed via a DPC-ranitidine complex, which decomposes slowly in a rate-determining step followed by other fast steps to give the products, which were identified as ranitidine sulfoxide by spot test and spectroscopic studies. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

One-pot reductive amination of aldehydes catalyzed by a hydrio-iridium(III) complex in aqueous medium

A combination of sodium tetrakis[3,5-di(trifluoromethyl)phenyl]borate [NaBAr^F₄] and hydrio-iridium(III) complex efficiently catalyzed the one-pot reductive amination of aldehydes with various amines and ammonia in water under mild conditions in good to excellent yields.     

Oxidation of L-phenylalanine by diperiodatoargentate(III) in aqueous alkaline medium. A Mechanistic approach

The kinetics of oxidation of L-phenylalanine (L-Phe) by diperiodatoargentate(III) (DPA) in alkaline medium at a constant ionic strength of 0.25 mol/dm⁻³ has been studied spectrophotometrically. The reaction between DPA and L-phenylalanine in alkaline medium exhibits 1: 1 stoichiometry (L-phenylalanine: DPA). The reaction shows first order in [DPA] and has less than unit order dependence each in both [L-Phe] and [Alkali] and retarding effect of [IO₄⁻] under the reaction conditions. The active species of DPA is understood to be as monoperiodatoargentate(III) (MPA). The reaction is shown to proceed via a MPA-L-Phe complex, which decomposes in a rate-determining step to give intermediates followed by a fast step to give the products. The products were identified by spot and spectroscopic studies. The reaction constants involved in the different steps of the mechanisms were calculated. The activation parameters with respect to slow step of the mechanism were computed and discussed. The thermodynamic quantities were also determined for the reaction.     

Separation of carbon nanotubes in aqueous medium by capillary electrophoresis

A robust and reproducible method for the dispersion of carbon nanotubes, either single-walled or multi-walled is presented. Dispersion of nanotubes was achieved as surfactant-coated species of sodium dodecyl sulphate. The addition of small amounts of hydroxypropyl methyl cellulose (HPMC) together with the surfactant, sodium dodecyl sulphate, was found critical to achieve reproducible nanotubes dispersion and to obtain an homogeneous and stable solution. This solution is further analyzed by capillary electrophoresis using a background electrolyte solution containing a polymer, 0.025% (w/v) HPMC solution prepared in 5 mM ammonium acetate at pH 8.03. This electrophoretic method presents a high reproducibility between runs, being an interesting alternative to study nanotube size distribution or characterization after synthesis. In addition, the methodology developed allowed the study of the interaction of the different types of carbon nanotubes with a molecular probe such as pentachlorophenol. This procedure was showed effective to detect small differences on the chemical/physical surface properties of the nanotubes. The different interaction behavior found within the two SWNTs selected was critically discussed.     

Voltammetric determination of As(III) in an aqueous zwitterionic complexing medium

Summary The polarographic behaviour and determination of As(III) in aqueous complexing electrolytes (bicine buffer solutions) ofpH values varying from 1.13–11.96 have been investigated at 25°C (direct current and differential pulse polarographic techniques). Using DC polarographic measurements, it was shown that reduction of As(III) takes place along one or three waves depending upon thepH value of the solution. Microcoulometric experiments have been performed at the limiting region of the different waves obtained at differentpH values. Cyclic voltammograms were recorded using a HDME to investigate the nature of reduction. Schemes for the mechanism of reduction occurring at the DME have been deduced. Kinetic parameters and wave characteristics for the reduction of As(III) have been calculated. A method for DPP determination of As(III) in bicine buffer solution ofpH 1.41 is reported. The detection limit of the method is 6.60×10^–8 M As(III).

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Voltammetrische Bestimmung von As(III) in einem wäßrigen zwitterionischen komplexierenden Medium

Zusammenfassung Das polarographische Verhalten und die polarographische Bestimmung von As(III) in wäßrigen komplexierenden Elektrolyten (Bicin-Pufferlösungen) wurde beipH-Werten zwischen 1.13 und 11.96 und 25°C untersucht (Direktstrom- und Differentialpulstechniken). Mittels DC-Polarographie wurde gezeigt, daß die Reduktion von As(III) je nach dempH-Wert der Lösung in einer oder in drei Wellen erfolgt. In den Grenzbereichen der bei verschiedenenpH-Werten erhaltenen unterschiedlichen Wellen wurden microcoulometrische Experimente durchgeführt. Zur Untersuchung des Reduktionsvorgangs wurden cyclische Voltammogramme unter Verwendung einer HDME durchgeführt. Für den Mechanismus der an der Quecksilbertropfelektrode stattfindenden Reduktion wurden Reaktionsgleichungen ermittelt. Kinetische Parameter und Wellencharakteristika für die Reduktion von As(III) wurden berechnet. Eine Methode zur Bestimmung von As(III) mittels differentieller Pulspolarographie in Bicin-Pufferlòsung beipH 1.14 wird vorgestellt. Die Erfassungsgrenze der Methode liegt bei 6.60×10^–8 M As(III).