Estimation of Dimethyl Sulphoxide and Submicrogram Quantities of Ruthenium (III) by Catalysis of the Cerium (IV)-Dimethy Sulphoxide Reaction in Aqueous Sulphuric Acid Media (original) (raw)
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International Journal of Chemical Kinetics, 1995
Kinetics of ruthenium(II1) chloride catalysed oxidation of acetone, ethylmethyl ketone, isobutylmethyl ketone, pentan-2-one, cyclopentanone and cyclohexanone by sodium metaperiodate in aqueous alkaline medium at constant ionic strenqth is reported. The order with respect to [IOjl is found to be zero. The order with respect to [substratel is unity for acetone, ethylmethyl ketone, isobutylmethyl ketone and cyclopentanone, whereas, pentan-2-one and cyclohexanone exhibit fractional deuendence on substrate, in the entire range of substrate concentration studied. Strikingly, the order with resnect to [ruthenium (1II)I is fractional in case of the ketones where substrate deoendence is unity and unity where the substrate dependence is fractional. The reaction rate increases linearly following a nearly unit dependence on [OH-1 at lower concentration of alkali and levels off after a particular [OH-]. The activation narameters have been evaluated. A suitable mechanism has been postulated and rate laws have been deduced.
The micro amounts of ruthenium(III) catalyzed oxidation of chloramphenicol by cerium(IV) in an aqueous sulphuric acid medium has been studied spectrophotometrically at 25°C and at I = 1.60 molÁdm -3 . The order with respect to [Ce(IV)] and [Ru(III)] was found to be unity. Increasing [H ? ] accelerates the rate with less than unit order in [H ? ]. The reaction rate decreases with increasing ionic strength and increases with decreasing dielectric constant of the medium. The experimental results suggest that the active species of cerium(IV) and ruthenium(III) were CeSO 4 2? and [Ru(H 2 O) 6 ] 3? , respectively. Based on the experimental results a suitable mechanism was proposed and the rate law was derived. The activation parameters were calculated with respect to the slow step of the proposed mechanism and thermodynamic quantities were also determined. The reaction constants involved in the mechanism have been computed. There is a good agreement between the experimental and calculated rate constants under different experimental conditions.
European Chemical Societies Publishing , 2024
This study investigates the kinetics of oxidative conversion of benzyl and homobenzyl alcohols to carbonyls using cerium(IV) sulfate in the presence of ruthenium(III) complex under mild acidic conditions. The results revealed that the low concentration of both alcohols and cerium(IV) ions drives the reaction to a first-order kinetics, whereas a higher concentration induces zero-order kinetics. In addition, the kinetics of the reaction were altered by the additives of hydrogen ions, cerium(III) ions, and chloride ions. We hope this study will be helpful in understanding the reaction kinetics of the oxidation of primary alcohols.
Preparation and characterization of highly active ruthenium sulphide supported catalysts
Catalysis Letters, 1990
Alumina supported ruthenium sulphide catalysts, thiophene hydrodesulphurization, XPS characterization Ruthenium sulphide catalysts supported on alumina were prepared using different precursor salts [ruthenium (III) chloride trihydrate, ruthenium (III) acetylacetonate and triruthenium dodecacarbonyl] and sulphided under various atmospheres. The properties of the catalysts in thiophene hydrodesulphurization are interpreted in relation to the XPS characterizations. These results show the importance of the sulphidation step in the absence of hydrogen in order to obtain a well sulphided, well dispersed and highly active catalyst.
2013
Department of Chemistry, University of Allahabad, Allahabad-211 002, Uttar. Pradesh, India <em>E-mail </em>: pktandon123@rediffmail.com <em>Manuscript received online 15 December 2012, revised 30 January 2013, accepted 07 February 2013</em> Oxidation of 2-phenyl ethanol and 2-methyl cyclohexanol by cerium(IV) sulphate in aqueous sulphuric acid medium is greatly enhanced by iridium(III) chloride. Catalyst combines with the complex formed between cerium(Iv) and organic substrate and ultimately gives rise to corresponding aromatic dicarboxylic acids as the product of oxidation. Reactions follows direct proportionality with respect to catalyst concentrations while the first order kinetics shown by the oxidant and organic substrate at their low concentrations become zero order at higher concentrations of both oxidant and organic substrate. Rate decreased with increasing concentrations of H<sup>+</sup> ions. Externally added Ce<sup>III </sup>...
Transition Metal Chemistry, 2008
The oxidation of antimony(III) by cerium(IV) has been studied spectrometrically (stopped flow technique) in aqueous sulphuric acid medium. A minute amount of manganese(II) (10-5 mol dm-3) is sufficient to enhance the slow reaction between antimony(III) and cerium(IV). The stoichiometry is 1:2, i.e. one mole of antimony(III) requires two moles of cerium(IV). The reaction is first order in both cerium(IV) and manganese(II) concentrations. The order with respect to antimony(III) concentration is less than unity (ca 0.3). Increase in sulphuric acid concentration decreases the reaction rate. The added sulphate and bisulphate decreases the rate of reaction. The added products cerium(III) and antimony(V) did not have any significant effect on the reaction rate. The active species of oxidant, substrate and catalyst are Ce(SO 4) 2 , [Sb(OH)(HSO 4)] + and [Mn(H 2 O) 4 ] 2+ , respectively. The activation parameters were determined with respect to the slow step. Possible mechanisms are proposed and reaction constants involved have been determined.
An XPS Study of the Promotion of Ru-Cs/Sibunit Catalysts for Ammonia Synthesis
Kinetics and Catalysis, 2005
The nature of surface cesium compounds in cesium-modified ruthenium-Sibunit catalysts for ammonia synthesis was studied by X-ray photoelectron spectroscopy (XPS). It was found that, on the reduction of promoted catalysts, cesium was incorporated into the micropores of Sibunit to form quasi-intercalation cesium-carbon bonds. In this case, the chemical state of cesium was close to its state in cesium suboxides. The subsequent interaction with atmospheric oxygen resulted in the oxidation of cesium, which occurred as cesium peroxide and cesium superoxide in the oxidized samples. Ruthenium occurred in a metallic state in the reduced samples. The activity of a Ru-Cs + /C(1) sample was higher than that of inactive Ru-Cs + /C(2). This is a consequence of the higher surface concentration of ruthenium, which is most likely due to an increase in the dispersity of metal particles, as well as of the higher probability of the interaction between the promoter and the active component due to a symbatic increase in the surface concentrations of both ruthenium and cesium.
Catalysis Letters, 2008
Sibunit-supported Ru-catalysts promoted with cesium or rubidium compounds have been comparatively studied with XPS. The cesium promoter interacts both with support and with active component. The absence of the promoter-support interaction in the case of rubidium provides a stronger interaction between promoter and active component compared to the cesium-based catalysts. These differences in the promoter-support and promoter-metal interactions are exhibited when a sequence of ruthenium and alkali introduction are changed.