Kinetics of oxidation of hypophosphite ion by Au(III) in hydrochloric acid medium

Sengupta, Kalyan K.; Basu, B. N.; SENGUPTA, S.; Nandi, Sanghamitra

doi:10.1016/s0277-5387(00)81441-2

Cited by 14 publications

(4 citation statements)

References 12 publications

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“…The oxidation of phosphorus acids by various oxidants involves either a single‐electron transfer or hydride abstraction . The hydride abstraction generally occurs when the oxidant undergo more than two electron change since in the present study [H 5 Co III Mo 5 O 20 ] 2− is a single‐electron oxidant; the direct electron transfer mechanism is preferred.…”

Section: Resultsmentioning

confidence: 71%

“…1) [15], and at a pH of 2.0 the added molybdate ion exists in the protonated form. The catalytic effect of the hydrogen ion concentration on the reaction is due to the The oxidation of phosphorus acids by various oxidants involves either a single-electron transfer [19][20][21] or hydride abstraction [22][23][24]. The hydride abstraction generally occurs when the oxidant undergo more than two electron change since in the present study [H 5 Co III Mo 5 O 20 ] 2− is a single-electron oxidant; the direct electron transfer mechanism is preferred.…”

Section: Resultsmentioning

confidence: 99%

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Oxidation of Hypophosphite and Phosphite by Anderson‐Type Hexamolybdocobaltate(III) Anion

Barge

Gokavi

2015

Int J of Chemical Kinetics

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The oxidation of hypophosphite and phosphite by the Anderson‐type hexamolybdocobaltate(III), [H6CoIIIMo6O24]3−, anion was investigated at pH 2 and 1, respectively, in aqueous medium. The reaction is found to occur through an outer‐sphere mechanism with a prior weak complex formation between the reactants. Under the reaction conditions, the oxidant exists in the [H5CoIIIMo5O20]2−, [H6CoIIIMo6O24]3−, and [H4CoIII2Mo10O38]6−(dimer) forms, and [H5CoIIIMo5O20]2− is the active species. Inhibition of the reaction by the oxidant anion and added molybdate ion kinetically indicates existence of prior equilibria between various forms of the oxidant. Both hypophosphite and phosphite exists in their protonated forms. The reaction involves direct electron transfer from the phosphorus center to the anion‐generating free radicals in a rate‐determining step. The effect of ionic strength and change in the solvent polarity did not affect the rate of the reaction. A probable mechanism was proposed leading to a complicated rate law as a result of involvement of prior equilibria between various forms of the oxidant. The activation parameters were also determined and are in support of the proposed mechanism.

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Section: Resultsmentioning

confidence: 71%

Section: Resultsmentioning

confidence: 99%

Oxidation of Hypophosphite and Phosphite by Anderson‐Type Hexamolybdocobaltate(III) Anion

Barge

Gokavi

2015

Int J of Chemical Kinetics

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“…The oxidations of phosphorus compounds have been studied with a variety of oxidants such as Bi(V), chloramine T, OH radicals, Ce(V), Ag(I), Ag(II), V(V), and AuCl 4 – . Formation of M–O–P intermediates as well as outer-sphere redox processes has been proposed.…”

Section: Introductionmentioning

confidence: 99%

Oxidation of Phosphorus Centers by Ferrate(VI): Spectral Observation of an Intermediate

et al. 2012

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The kinetics and mechanism for the oxidation of phosphite, hypophosphite, phenylphosphite, and trimethylphosphite by ferrate(VI) are reported. Hypophosphite is rapidly oxidized to phosphite which is slowly oxidized to phosphate, trimethylphosphite is oxidized to trimethylphosphate, and phenylphosphite is oxidized phenylphosphate. (18)O induced shifts of the (31)P NMR signals support oxygen transfer from ferrate(VI) to the phosphorus center during the oxidation process. Deuteration of the hydridic hydrogens in hypophosphite and phosphite resulted in significant kinetic isotope effects on the reaction rates. It is proposed that ferrate(VI) acts as a two-electron oxidant in conjunction with oxide transfer coupled with phosphorus hydrogen bond breaking for phosphite and hypophosphite and simple oxygen transfer for trimethylphosphite and phenylphosphite.

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“…Apart from the above therapeutic use, the redox properties of Au(III)–Au(I) couple have also been utilized for catalytic appilcations 4. Reduction of gold(III) either to the metallic state or to gold(I) have been investigated 5–14 kinetically while oxidation 15 of gold(I) is scarce. The reason may be due to the disproportionation of gold(I) that is catalyzed by the surfaces 7 of the container.…”

Section: Introductionmentioning

confidence: 99%

Kinetics and mechanism of oxidation of aurate(I) by peroxydisulphate in aqueous hydrochloric acid

Babshet

Gokavi

2002

Int J of Chemical Kinetics

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The reaction between Au(I), generated by reaction of thallium(I) with Au(III), and peroxydisulphate was studied in 5 mol dm −3 hydrochloric acid. The reaction proceeds with the formation of an ion-pair between peroxydisulphate and chloride ion as the Michealis-Menten plot was linear with intercept. The ion-pair thus formed oxidizes AuCl 2 − in a slow two-electron transfer step without any formation of free radicals. The ion-pair formation constant and the rate constant for the slow step were determined as 113 ± 20 dm −3 mol −1 and 5.0 ± 1.0 × 10 −2 dm 3 mol −1 s −1 , respectively. The reaction was retarded by hydrogen ion, and formation of unreactive protonated form of the reductant, HAuCl 2 , causes the rate inhibition. From the hydrogen ion dependence of the reaction rate, the protonation constant was calculated to be as 0.6 ± 0.1 dm 3 mol −1 . The activation parameters were determined and the values support the proposed mechanism.

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Kinetics of oxidation of hypophosphite ion by Au(III) in hydrochloric acid medium

Cited by 14 publications

References 12 publications

Oxidation of Hypophosphite and Phosphite by Anderson‐Type Hexamolybdocobaltate(III) Anion

Oxidation of Hypophosphite and Phosphite by Anderson‐Type Hexamolybdocobaltate(III) Anion

Oxidation of Phosphorus Centers by Ferrate(VI): Spectral Observation of an Intermediate

Kinetics and mechanism of oxidation of aurate(I) by peroxydisulphate in aqueous hydrochloric acid

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