Kinetic study of ruthenium(VI) -- catalyzed oxidation of 2-methoxy- ethanol by aqueous alkaline hexacyanoferrate(III)

The kinetics of ruthenium(VI) catalyzed oxidation of 2-methoxyethanol by hexacyanoferrate(III) ion in an aqueous alkaline medium at constant ionic strength shows zero order dependence on hexacyanoferrate(III) and first order dependence on Ru(VI). Dependence of substrate concentration shows a Michaelis – Menten type behaviour. The rate increases with the decrease in alkali concentration. A reaction mechanism involves the formation of an intermediate complex between the substrate and ruthenium(VI). This complex decomposes slowly, producing ruthenium(IV), which is reoxidized by hexacyanoferrate(III) in subsequent steps. The theoretical rate law obtained is in complete agreement with the experimental observations.     

Rhodium(III) catalyzed oxidation of cyclic ketones by alkaline hexacyanoferrate(III)

The kinetics of the oxidation of 2-methyl cyclohexanone and cycloheptanone with Fe(CN)₆ ³⁻ catalyzed by RhCl₃ in alkaline medium was investigated at four temperatures. The rate follows direct proportionality with respect to lower concentrations of hexacyanoferrate(III) ion, but tends to become zero order at higher concentrations of the oxidant, while the reaction shows first-order kinetics with respect to hydroxide ion and cyclic ketone concentrations. The rate shows a peculiar nature with respect to RhCl₃ concentrations in that it increases with increase in catalyst at low catalyst concentrations but after reaching a maximum, further increase in concentration retards the rate. An increase in the ionic strength of the medium increases the rate, while increase in the Fe(CN)₆ ⁴⁻ concentration decreases the rate.     

Kinetic study of Ru(VI)-catalyzed oxidation of cyclic alcohols by hexacyanoferrate(III) in aqueous alkaline medium

The kinetics of the oxidation of cyclopentanol, cyclohexanol, 2? methylcyclohexanol, and cycloheptanol by hexacyanoferrate(III) ions in mild alkaline medium has been studied in the presence of traces of ruthenium(VI) ≈ 10^?7M at constant ionic strength (0.26M). The results suggest that the oxidation of the studied cyclic alcohols proceeds via the formation of a complex between Ru(VI) and the substrate which slowly decomposes, giving the reduced form of ruthenium which was reoxidized to Ru(VI) in a fast step by alkaline hexacyanoferrate(III) ions. The product study shows the production of the corresponding ketone.     

Kinetics and mechanism of the ruthenium(III)-catalysed oxidation of aminoalcohols by alkaline hexacyanoferrate(III)

Summary The kinetics of the ruthenium(III)-catalysed oxidation of aminoalcoholsviz. 2-aminoethanol and 3-aminopropanol by alkaline hexacyanoferrate(III) has been studied spectrophotometrically. The reactions are rapid initially, then follow a second order rate dependence with respect to each of the catalyst and the oxidant. The second order rate dependence with respect to ruthenium(III) was observed for the first time. The order in [Aminoalcohol] and [OH^–] is unity in each case. A suitable mechanism, consistent with the observed kinetic data is postulated.     

Ruthenium(VI)-catalysed oxidation of diols by alkaline hexacyanoferrate(III) ion. A kinetic study

The kinetics of Ru^VI-catalysed oxidation of ethane-1,2-diol, propane-1,3-diol, butane-1,3-diol, butane-1,4-diol and 2-butoxyethanol by hexacyanoferrate(III) ion in an aqueous alkaline medium at constant ionic strength shows zeroth order dependence on hexacyanoferrate(III) and first order dependence on Ru^VI and substrate. The results suggest that a complex is formed, between Ru^VI and the diol, which slowly decomposes to a reduced form of ruthenium, which is reoxidized to Ru^VI in a fast step by alkaline hexacyanoferrate(III). A plausible reaction mechanism is proposed.     

Ruthenium(VI) catalyzed oxidation of sodium salts of lactic, tartaric and glycolic acid by alkaline hexacyanoferrate(III)

The kinetics of ruthenium(VI) catalyzed oxidation of sodium salts of lactic, tartaric and glycolic acid by hexacyanoferrate(III) in aqueous alkaline medium have been studied at constant ionic strength. The reaction shows first order dependence on ruthenium(VI) and zero order on hexacyanoferrate(III). The rate of reaction increases with increasing substrate concentration and shows Michaelis-Menten type behavior. The rate of reaction decreases with increase in hydroxide ion concentration. Oxidation proceeds via formation of a complex between substrate and ruthenium(VI). A probable mechanism is suggested.

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(VI) , (III) . (VI) (III). -. . (VI). .

     

Kinetics and mechanism of the oxidation of butane-2,3-diol by alkaline hexacyanoferrate (III), catalyzed by ruthenium trichloride

The kinetics of oxidation of butane-2,3-diol by alkaline hexacyanoferrate (III), catalyzed by ruthenium trichloride has been studied spectrophotometrically. The reaction rate shows a zero-order dependence on oxidant, a first-order dependence on |Ru(III)|_T, a Michaelis-Menten dependence on |diol|, and a variation complicated on |OH⁻|. A reaction mechanism involving the existence of two active especies of catalyst, Ru(OH)₂⁺ and Ru(OH)₃, is proposed. Each one of the active species of catalyst forms an intermediate complex with the substrate, which disproportionates in the rate determining step. The complex disproportionation involves a hydrogen atom transfer from the α C(SINGLE BOND)H of alcohol to the oxygen of hydroxo ligand of ruthenium, to give Ru(II) and an intermediate radical which is then further oxidized. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 1–7, 1997.     

Kinetics of the Ru(III) catalyzed oxidation of formaldehyde and acetaldehyde by alkaline hexacyanoferrate(III)

The kinetics of ruthenium(III) catalyzed oxidation of formaldehyde and acetaldehyde by alkaline hexacyanoferrate(III) has been studied spectrophotometrically. The rate of oxidation of formaldehyde is directly proportional to [Fe(CN) _3– ⁶ ] while that of acetaldehyde is proportional tok[Fe(CN) _3– ⁶ ]/{k +k[Fe(CN) _3– ⁶ ]}, wherek, k andk are rate constants. The order of reaction in acetylaldehyde is unity while that in formaldehyde falls from 1 to 0. The rate of reaction is proportional to [Ru(III)] _T in each case. A suitable mechanism is proposed and discussed.

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Die Kinetik der Ru(III)-katalysierten Oxidation von Formaldehyd und Acetaldehyd mittels alkalischem Hexacyanoferrat(III)

Zusammenfassung Die Untersuchung der Kinetik erfolgte spektrophotometrisch. Die Geschwindigkeitskonstante der Oxidation von Formaldehyd ist direkt proportional zu [Fe(CN) _3– ⁶ ], währenddessen die entsprechende Konstante für Acetaldehyd proportional zuk[Fe(CN) _3– ⁶ ]/{k +k[Fe(CN) _3– ⁶ ]} ist, wobeik,k undk Geschwindigkeitskonstanten sind. Die Reaktionsordnung für Acetaldehyd ist eine erste, die für Formaldehyd fällt von erster bis zu nullter Ordnung. Die Geschwindigkeitskonstante ist in jedem Fall proportional zu [Ru(III)] _T . Es wird ein passender Mechanismus vorgeschlagen.

     

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.     

Kinetics and mechanism of the ruthernium(III) catalyzed oxidation of propane-1,3-diol by alkaline hexacyanoferrate(III)

The kinetics of oxidation of propane-1,3-diol by alkaline hexacyanoferrate (III) catalyzed by ruthenium trichloride has been studied spectrophotometrically. A reaction mechanism involving the formation of an intermediate complex between the substrate and the catalyst is proposed. In the rate-determining step this complex is attacked by hexacyanoferate(III) forming a free radical which is further oxidized.     

Catalytic kinetic determination of ultratrace amounts of ruthenium(III) based on the oxidation of benzylamine by alkaline hexacyanoferrate(III)

A kinetic method is proposed for the determination of ruthenium(III) by means of its catalytic effect on the oxidation of benzylamine by hexacyanoferrate(III) in alkaline medium. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance of hexacyanoferrate(III) at 420 nm. Under the optimum experimental conditions ruthenium(III) can be determined in the range 10-121 ng/ml with an average error of 1.7% and maximum relative standard deviation of 1.3%. The influence of many potential interferents has been examined and the method has been tested for determination of ruthenium(III) in synthetic mixtures. The method is convenient, reliable and rapid.     

Kinetic, mechanistic and spectral studies for the oxidation of sulfanilic acid by alkaline hexacyanoferrate(III)

The kinetics of oxidation of sulfanilic acid (p-aminobenzenesulfonic acid) by hexacyanoferrate(III) in alkaline medium was studied spectrophotometrically. The reaction showed first order kinetics in hexacyanoferrate(III) and alkali concentrations and an order of less than unity in sulfanilic acid concentration (SAA). The rate of reaction increases with increase in alkali concentration. Increasing ionic strength increases the rate but the dielectric constant of the medium has no significant effect on the rate of the reaction. A retarding effect was observed by one of the products i.e. hexacyanoferrate(II) (HCF(II)). A mechanism involving the formation of a complex between sulfanilic acid and hexacyanoferrate(III) has been proposed. The reaction constants involved in the mechanism are evaluated. There is a good agreement between the observed and calculated rate constants under different experimental conditions. Investigations at different temperatures allowed the determination of the activation parameters with respect to the slow step of the proposed mechanism.     

Mechanistic study of the oxidation of <Emphasis Type=SmallCaps>l</Emphasis>-phenylalanine by hexacyanoferrate(III) catalyzed by iridium(III) in aqueous alkaline medium

The oxidation of l-phenylalanine by hexacyanoferrate(III) (abbreviated as HCF) catalyzed by Ir(III) has been studied spectrophotometrically at 35 °C and at a constant ionic strength of 0.50 mol dm⁻³. The main oxidation product was identified as phenylpyruvic acid by physico-chemical and spectroscopic methods. The stoichiometry was found to be 2:1, i.e. 2 mol of hexacyanoferrate(III) reacted with 1 mol of phenylalanine. The reaction was first order with respect to both HCF and alkali concentration. The order with respect to [Phe] changed from first to zero as the concentration was increased. The effect of ionic strength was also investigated. Thermodynamic parameters were evaluated by studying the reaction at four different temperatures between 35 and 50 °C. Based on the experimental results, a suitable mechanism involving complex formation has been proposed.     

Kinetics and mechanism of oxidation of quinol by alkaline hexacyanoferrate(III)

The reaction between quinol and alkaline hexacyanoferrate(III) at constant ionic strength gives p-benzoquinone. The rate of the reaction was first order in the concentrations of substrate, oxidant and alkali. The slow step of the reaction involves the formation of the p-benzosemiquinone radical, which was detected by esr spectroscopy as a five-line spectrum with peak intensity ratios of 14641.

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(III) -. , . - , , 14641.

     

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.     

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.     

Un-catalyzed oxidation of cyclic ketones by alkaline hexacyanoferrate(III) - Kinetic evidence for the formation of hydrates

Hydrate formation by cyclic ketones confirmed by kinetic and spectral studies shows reduction of hexacyanoferrate(III) after the slow step. Orders and rate constants were confirmed by various methods.     

Oxidation of chromium(III) by alkaline hexacyanoferrate(III)

Alkaline hexacyanoferrate(III) oxidation of freshly prepared solutions of Cr^III (pH>12) at 27°C follows the rate law, Equation 1: