Kinetics of the vanadium(V) oxidation of phosphorous acid
01 Jan 1974-Journal of The Chemical Society-dalton Transactions (The Royal Society of Chemistry)-Iss: 2, pp 226-229
TL;DR: In this article, the reaction is initiated by formation of free radicals in the slow rate-determining step, and the effect of dielectric constant on the rate indicates that it is of the ion-dipole type.
Abstract: Kinetics of the oxidation of phosphorous acid by vanadium(V) over a temperature range of 40–55 °C have been studied. The reaction is first order with respect to vanadium(V) and phosphorous acid. The reaction is acid catalysed and is faster in sulphuric than perchloric acid. The order of the reaction with respect to mineral acid, when [Acid]⩽ 5·5M, is two. The effect of dielectric constant on the rate indicates that the reaction is of the ion–dipole type. Activation parameters have been evaluated. The reaction is initiated by formation of free radicals in the slow rate-determining step.
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TL;DR: In this article, the authors investigated the kinetics of oxidation of some aldoses by vanadium(V) in perchloric acid media and suggested a mechanism in which vanadium reacts with the aldose by a fast step to form a transition state, followed by the decomposition of the latter to give the products of reaction in a slow step.
Abstract: The kinetics of oxidation of some aldoses by vanadium(V) in perchloric acid media have been investigated. Each reaction is first order with respect to both [Vanadium(V)] and [Aldose]. The reactions are catalysed by acid. The addition of sodium perchlorate accelerates the rate of reaction. Kinetic evidence for the formation of an intermediate compound between vanadium(V) and aldoses is insignificant, and a mechanism is suggested in which vanadium(V) reacts with the aldoses by a fast step to form a transition state, followed by the decomposition of the latter to give the products of reaction in a slow step. The formation of free-radical intermediates has been demonstrated, and one-electron reduction of vanadium(V) by aldoses seems to be the most plausible mechanism. The oxidation rates follow the order: xyloses arabinose galactose mannose. The activation parameters are reported.
40 citations
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TL;DR: In this article, the authors studied the first order reaction in both hydroxylamine and platinum(IV) and showed that the rate increases with decreasing acidity and dielectric constant.
Abstract: The kinetics of the oxidation of hydroxylamine by platinum(IV) have been studied spectrophotometrically in sodium acetate-acetic acid buffer in the temperature range 25–40°C. The reaction is first order in both hydroxylamine and platinum(IV). The rate increases with decreasing acidity and dielectric constant. Different activation parameters of the reaction have been evaluated. Some possible reaction steps have been suggested.
28 citations
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TL;DR: In this article, the enthalpy and entropy of activation have been calculated to be 10·5 ± 0·5 kcal mole −1 and −24·5 −1·0 (e.g.
Abstract: Kinetic studies of the oxidation of hydrazine by chromic acid were made under various experimental conditions. The enthalpy and entropy of activation have been calculated to be 10·5 ± 0·5 kcal mole −1 and −24·5 ± 1·0 (e.u.) respectively and an attempt has been made to correlate activation parameters with those of the chromic acid oxidations of some phosphorus(III) and arsenic(III) compounds. The data suggest that oxidation follows formation of a complex between N 2 H 5 + and the reacting species of chromium(VI) in the rate determining step. The decomposition of the complex by a fast step gives the reaction products. Various mechanistic possibilities have been suggested.
12 citations
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01 Oct 1992
TL;DR: In this paper, the effect of solvent composition on reaction rate has been investigated and it has been concluded that the reaction proceeds through the pentacoordinated tautomer of the oxyacid.
Abstract: Oxidation of three lower oxyacids of phosphorus, viz. phosphinic, phenylphosphinic and phosphorous acids by pyridinium hydrobromide perbromide (PHPB), is first-order with respect to both oxyacid and PHPB. There is no effect on addition of acylonitrile and pyridinium bromide. On oxidation, deuterated phosphinic and phosphorous acids exhibit substantial kinetic isotope effects. The effect of solvent composition on reaction rate indicates that the transition state is more polar than the reactants. Reaction rates were determined at different temperatures and the activation parameters calculated. Alternative mechanisms, involving the two tautomeric forms of the oxyacid, have been formulated and it has been concluded that the reaction proceeds through the pentacoordinated tautomer. Transfer of a hydride ion from the oxyacid to PHPB, in the rate-determining step, has been proposed.
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TL;DR: In this article, the reaction is initiated by formation of free radicals in the slow rate-determining step, and the effect of dielectric constant on the rate indicates that it is of the ion-dipole type.
Abstract: Kinetics of the oxidation of phosphorous acid by vanadium(V) over a temperature range of 40–55 °C have been studied. The reaction is first order with respect to vanadium(V) and phosphorous acid. The reaction is acid catalysed and is faster in sulphuric than perchloric acid. The order of the reaction with respect to mineral acid, when [Acid]⩽ 5·5M, is two. The effect of dielectric constant on the rate indicates that the reaction is of the ion–dipole type. Activation parameters have been evaluated. The reaction is initiated by formation of free radicals in the slow rate-determining step.