Kinetics and mecahnism of oxidation of benzoins by peroxydisulfate catalyzed by Ag(I)

The kinetics of Ag(I) catalyzed oxidation of benzoin and four substituted benzoins by peroxydisulfate have been investigated in 30 vol. % acetic acid-water mixture at constant ionic strength. The parameters of Arrhenius and transition state theories have been computed. The rate laws are explained on the basis of a free radical mechanism.

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, Ag(I), (30 .%) . . - .

     

Kinetics of acid catalyzed and Ag(I) catalyzed decomposition of peroxodisulfate in aqueous medium

The mechanism of acid catalyzed decomposition of peroxodisulfate, (S₂O) in aqueous perchlorate medium involves the hydrolysis of the species H₂S₂O₈ and HS₂O and the homolysis of the species H₂S₂O₈, HS₂O and S₂O at the O? O bond. The overall rate law when 1.4M > [HClO₄] > 0.1M is The constants k′ and k″ contain the hydrolysis and homolysis rate constants of HS₂O₈^? and H₂S₂O₈, respectively. With added Ag(I), the acid catalyzed and Ag(I) catalyzed reactions take place independently. Ag(I) catalyzed decomposition appears to involve the species AgS₂O (aq).     

Kinetics of oxidation of Indigo Carmine by potassium peroxydisulfate

The reaction is first order in potassium peroxydisulfate and zero order in Indigo Carmine. Hydrogen ions have no effect on the rate in the acidity range of 0.0–0.2 M. Allyl acetate inhibits the reaction. A radical chain mechanism is proposed.

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. 0 0,2 M . . .

     

Kinetics and mechanism of silver(I) catalyzed oxidation of coordinated formate by peroxydisulphate

Summary The oxidation of coordinated formate in the complexcis [Co(en)₂(NH₂R)(O₂CH)]²⁺ (R=H, Me or Et) by peroxydisulphate is catalyzed by Ag⁽¹⁾. Comparison between the rates of oxidation and of acid catalyzed equation of the formato complexes shows that the former is not substitution controlled. The observed pseudo first order rate constant was found to be first order with respect to the concentration of each of the reactantsi.e. the complex, Ag⁽¹⁾, and the oxidant. The rate and activation parameters for the oxidation process are reported. The major product of oxidation was found to be thecis(aquo)pentamine cobalt(III) [cis[Co(en)₂(NH₂R)OH₂]³⁺]; cobalt(II) was produced only <5%. The oxidation largely involves two electron transfer from the formate ligand, which is consistent with the hydride transfer mechanism.     

Kinetics and mechanism of oxidation of sulfasomidine by peroxydisulfate ion

Results of the kinetic studies of peroxydisulfate ion oxidation of sulfasomidine (N-(2,6-dimethyl-4-pyrimidyl)-4-aminobenzenesulfonamide) in aqueous medium are discussed. N,N-bis(2,6-dimethyl-4-pyrimidyl)azoxybenzene-p,p-disulfonamide has been identified as the main oxidation product. On the basis of product identification and kinetic studies a radical mechanism has been proposed.

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(N-(2,6--4-)-4--) . N,N-(2,6--4-)--,-. .

     

Kinetics and mechanism of oxidation of sulfaguanidine by peroxydisulfate ion

Results of the kinetic studies of peroxydisulfate ion oxidation of sulfaguanidine are discussed. N,N'-bis(guanyl)azoxybenzene-p,p'-disulfonamide has been identified as the main oxidation product. On the basis of product identification and kinetic studies a radical mechanism is proposed.

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. N,N'- () -, '- . , .

     

Kinetics and orientation in the peroxydisulfate oxidation of phenol

Oxidation of phenol by aqueous alkaline peroxydisulfate to form o⁻ and p-dihydroxybenzenes has been studied. The rate is expressed as: v = k[s₂O₈⁼[PhOH], where the k value tends to increase with an increase of the concentration of alkali and a plot of log k vs pH at pH 9·5-10 is a straight line with a slope of ca unity. The effects of ionic strength, concentration of alkali and temperature on the o/p ratio has been determined. In view of these facts a probable mechanism involving a nucleophilic attack of a C atom of phenoxide ion on the peroxide oxygen of the peroxydisulfate ion has been postulated and discussed.     

Kinetics of p-xylene oxidation catalyzed by cobalt oxide

Kinetics of p-xylene oxidation in an aqueous system catalyzed by cobalt oxide have been studied at 140 °C under oxygen. The reaction is second order in p-xylene and first order in cobalt oxide concentration. The rate constant and product distribution are very close to those found for homogeneous catalytic reactions. Based on these findings, a reaction scheme describing the influence of oxide catalyst is formulated. - , , 140° C . - . , . , .     

Kinetics and mechanism of Os(VIII) catalyzed oxidation of dimethyl sulfoxide by vanadium(V)

The title reaction is first order each in vanadium(V) and Os(VIII) and fractional order with respect to DMSO. The rate is found to decrease with increasing concentrations of sulfuric, perchloric and acetic acid, whereas the rate increases with the increasing concentrations of sodium bisulfate and sodium perchlorate. Thermodynamic parameters like E_a, H, S and G were evaluated. A suitable mechanism consistent with the observed kinetics is proposed.     

Kinetics and mechanism of palladium(II) catalyzed chromium(VI) oxidation of mercury(I) in aqueous sulphuric acid

The Cr^VI oxidation of Hg^I in an aqueous acid medium occurs to a modest extent only in presence of Pd^II and in H₂SO₄ above ca. 0.20 mol dm^–3. The reaction is first order in [Cr^VI] in the presence of Pd^II catalyst. The order in [Hg^I] is less than unity, whereas that in [Pd^II] is unity. Increase in [H₂SO₄] accelerates the reaction rate. The added products, Cr^III and Hg^II, do not significantly effect the reaction rate. A mechanism involving HCrO₄ ^– and PdCl⁺ as the reactive species of oxidant and catalyst respectively, is proposed. The reaction constants involved in the mechanism have been evaluated.     

Kinetics and mechanism of osmium(VIII) catalyzed oxidation of tellurium(IV) by cerium(IV)

The reaction is first order in substrate and catalyst and zero order in cerium(IV). The rate decreases with increasing [H⁺] as well as with increasing ionic strength. H and S have been found to be 44.8 kJ mol^–1 and 161.8 JK^–1 mol^–1 respectively. A mechanism is proposed.

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(IV). [H⁺], . , H S 44,8 ·^–1 161,8 ·^–1–1, . .

     

Kinetics and mechanism of ruthenium(III) catalyzed oxidation of tellurium(IV) by cerium(IV)

The reaction is zero order in cerium(IV), fractional order in tellurium(IV) and first oder in ruthenium(III). While the ionic strength has no effect, the rate increases with increasing [H⁺], and decreases with increasing [HSO ₄ ^– ]. H and S are 54.4 kJ mol^–1 and –60.3 JK^–1 mol^–1, respectively. A suitable mechanism is proposed.

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(IV), (IV) (III). , [H⁺] [HSO ₄ ^– ]. H S 54,4 ^–1 –60,3 ·^–1·^–1, . .

     

Ag(I) catalyzed and uncatalyzed oxidation of dimethyl sulfoxide by ceric nitrate in nitric acid medium: A kinetic study

The uncatalyzed oxidation of dimethyl sulfoxide (DMSO) by Ce(IV) involves complex formation between them in nitric acid medium which yields final products. The orders in [Ce(IV)] and [DMSO] were one and fractional, respectively. With Ag(I) as catalyst, an Ag(I)-DMSO adduct is proposed. This adduct reacts with Ce(IV) bimolecularly to give a Ag(II)-DMSO adduct which finally yields the products. The rates exhibit fractional order in [Ag(I)] as well as [DMSO] and first order in [Ce(IV)].

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(DMSO) Ce(IV) , . [Ce(IV)] , [DMSO]—. Ag(I) , Ag(I)–DMSO. Ce(IV) , Ag(II)–DMSO, . [Ag(I)], [DMSO], [Ce(IV)].

     

Kinetics and mechanism of oxidation of benzoic acid hydrazide by bromate catalyzed by octamolybdomanganate(II)

Oxidation of benzoic acid hydrazide by bromate in the presence of octamolybdomanganate(II), [Mn^IIMo₈O₂₇]⁴⁻, was studied in hydrochloric acid medium. The mechanism of the reaction involves oxidation of the catalyst to [Mn^IVMo₈O₂₇]²⁻ by bromate which then forms a complex with the unoxidized catalyst. Both the complex and [Mn^IVMo₈O₂₇]²⁻ react with the substrate in rate-determining steps to generate an intermediate acyl diimide, RCONNH. The reaction of water with the diimide then leads to the formation of benzoic acid and nitrogen as products through an NH–NH intermediate. There was no formation of free radical, indicating the involvement of only two-electron transfer steps in the mechanism. The order of more than unity in catalyst concentration is due to the formation of complex between the catalyst and the oxidized form of the catalyst. A rate law explaining all the kinetic results has been derived and verified. The effects of ionic strength and solvent polarity have also been studied, and the thermodynamic parameters were determined. A less solvated transition state as a result of interaction between the complex and oxidized form of the catalyst satisfactorily explains all the effects observed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.