Kinetics and mechanism of TI(III) oxidation of cellobiose in acidic medium

TI(III) oxidation of cellobiose in the presence of H₂SO₄ in aqueous acetic acid is first order in each reactant and is acid catalyzed. TI(OAc) ₂ ⁺ is the active species. Products identified are gluconic acid and glucose. A mechanism consistent with the temperature, solvent, acidity and salt effects is been proposed.

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TI(III) H₂SO₄ . TI(OAc) ₂ ⁺ . . , , , .

     

Kinetics and mechanism of oxidation of phenylhydrazine and P-bromophenylhydrazine by hexacyanoferrate(III) in acidic medium

Kietics of oxidation of phenylhydrazine and p-bromophenylhydrazine by hexacyanoferrate(III) in acidic medium have been studied. The reactions follow similar kinetics, being first order with respect to both hydrazine and exacyanoferrate(III) and inverse first order with respect to the hydrogen ion. Addition of hexacyanoferrate(II) has no retarding effect on the rate of oxidation. The effects of varying ionic strength, dielectric constant, and temperature on the reaction rates have been investigated. A plausible mechanism has been proposed to account for the experimental results. Benzene and bromobenzene have been identified as the oxidation products.     

Kinetics and mechanism of oxidation of paracetamol by an Anderson-type 6-molybdocobaltate(III) in acidic medium

Transition Metal Chemistry - Oxidation of paracetamol by the Anderson-type hexamolybdocobaltate(III) anion [H6CoIIIMo6O24]3− was investigated at pH values of 1 and 2 in aqueous medium. The...     

The oxidation of carbohydrazide by the 12-tungstocobaltate(III) ion in acidic medium: Kinetics and mechanism

The redox reaction between the 12-tungstocobaltate(III) ion and carbohydrazide is first order with respect to both the oxidant and the substrate. The observed pseudo first-order rate constant, k_obs, is retarded by increasing the concentrations of H⁺ and alkali metal ion (Li⁺, Na⁺ and K⁺). There is a linear correlation between the k_obs and the concentrations of carbohydrazide and H⁺ ion, but the plots of k_obs against the concentrations of the alkali metal ions is non-linear. However, the same data is applicable to the Davies equation for the effect of the ionic strength on the k_obs.     

Kinetics and mechanism of the oxidation of halotoluenes by acidic hexacyanoferrate(III)

The oxidation of halotoluenes by hexacyanoferrate(III) in aqueous acetic acid containing perchloric acid (0.5M) at 50°C gave the corresponding aldehyde as the major product, and a small amount of polymeric material. The order with respect to each of the reactants—substrate, oxidant, and acid—was found to be unity. Increasing proportions of acetic acid increased the rate of the reaction. The reaction was influenced by changes in temperature, and the activation parameters have been evaluated. The Hammett plot yielded a ρ⁺ value of ?1.8. A kinetic isotope effect k_H/k_D = 6.0 has been observed. The pathway for the conversion of the halotoluenes to the products has been mechanistically visualized as proceeding through the benzylic radical intermediate, formed in the rate-determining step of the reaction. The radical undergoes rapid conversion to the products.     

Manganese(III) oxidation of L‐serine in aqueous sulfuric acid medium: Kinetics and mechanism

Kinetics and mechanism of oxidation of L‐serine by manganese(III) ions have been studied in aqueous sulfuric acid medium at 323 K. Manganese(III) sulfate was prepared by an electrolytic oxidation of manganous sulfate in aqueous sulfuric acid. The dependencies of the reaction rate are: an unusual one and a half‐order on [Mn(III)], first‐order on [ser], an inverse first‐order on [H⁺], and an inverse fractional‐order on [Mn(II)]. Effects of complexing agents and varying solvent composition were studied. Solvent isotope studies in D₂O medium were made. The dependence of the reaction rate on temperature was studied and activation parameters were computed from Arrhenius‐Eyring plots. A mechanism consistent with the observed kinetic data has been proposed and discussed. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 525–530, 1999     

Kinetics and mechanism of oxidation of antimony(III) by keggin‐type 12‐tungstocobaltate(III) in aqueous hydrochloric acid medium

The reaction between Sb(III) and [Co^IIIW₁₂O₄₀]^5? proceeds with two, one‐electron steps; formation of unstable Sb(IV) is the slow first step followed by its reaction with another oxidant in a fast step. The reaction rate is unaffected by the [H⁺] as there are no protonation equlibria involved with both the reactants, whereas the accelerating effect of chloride ion is due to the formation of an active chlorocomplex of the reductant, SbCl₆^3?. Increase in the ionic strength and decrease in the relative permittivity of the medium increases the rate of the reaction, which is attributed to the formation of an outer‐sphere complex between the reactants. The activation parameters were also determined and these values support the proposed mechanism. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 9–14, 2003     

Kinetics and mechanism of oxidation of quinols by tris(1,10-phenanthroline) iron(III) complexes in aqueous acidic perchlorate media

The kinetics of oxidation of several substituted quinols by a series of Tris(1,10-phenanthroline)iron(III) complexes has been investigated with a stopped-flow technique at 6.0 and 20.0°C. The reactions were found to be first order on both reactants and independent of acidity. The second-order specific rate constants were strongly dependent on free energy of reaction. An interpretation of the mechanism in the light of Marcus theory has been developed. The first electron abstraction with semiquinone radical formation has been suggested as the rate-determining step, and on this basis, intrinsic parameters of the reactions have been derived. A good agreement was found between experimental and computed data.     

碱性介质中二过碲酸合铜(III)氧化乙二醇的反应动力学及机理

本文采用分光光度法研究了碱性介质中二过碲酸合铜(III)(DTC)氧化乙二醇(Glgcol)在291.2-303.2K的反应动力学机理。结果表明, 反应对氧化剂(DTC)是一级, 对乙二醇也是一级, 准一级([Glycol]0>>[DTC]0)速率常数Kobs随着[OH^-]增加而增加, 随着[TeO4^2^-]增加而降低, 并且有负盐效应, 提出了一种含有前期平衡的反应机理。据此导出了一个能够解释全部实验事实的速率方程, 求出平衡常数、速控步骤的速率常数及298.2K时的活化参数。     

Kinetics and mechanism of the complexation between hydroxopentaaquochromium(III) and octacyanomolybdate(IV) ions in acidic medium

Summary The reaction between hydroxopentaaquochromium(III) and octacyanomolybdate(IV) was investigated spectrophotometrically and obeyed a 2:1 reactant stoichiometry with respect to formation of the [Cr(H₂O)₄OH]₂ Mo(CN)₈ complex. Kinetic studies reveal that the reaction is first order with respect to hydroxopentaaquochromium(III) in the presence of an excess of octacyanomolybdate(IV). The reaction rate increased with an increase in the ionic strength and temperature, and decreased with an increase in hydrogen ion concentration. A mechanism has been proposed based upon ion-pair formation. The results are best accounted for by the Eigen-Tamm mechanism. Anation of [Cr(H₂O)₅OH]²⁺ is discussed in terms of an associative interchange (I _a) where bond breaking and bond making are equally important. The activation parameters were calculated using Arrhenius's equation.     

Kinetics and mechanism of the oxidation of iodide by diaquote- trakis(2,2′-bipyridine)-μ-oxodiruthenium(III) ion in acid medium

Transition Metal Chemistry - The kinetics of the oxidation of iodide by diaquotetrakis-(2,2-bipyridine)-μ-oxodiruthenium(III), [Ru2O]4+, were studied in aqueous perchloric acid at...     

Kinetics and mechanism of oxidation of iodide with a (μ‐oxo)diiron(III,III) complex in weakly acidic media

The complex ion [Fe^III₂(μ‐O)(phen)₄(H₂O)₂]⁴⁺ ( 1 ) (phen = 1,10‐phenanthroline) and its hydrolytic derivatives [Fe^III₂(μ‐O)(phen)₄(H₂O)(OH)]³⁺ ( 1a ) and [Fe^III₂(μ‐O)(phen)₄‐ (OH)₂]²⁺ ( 2a ) coexist in rapid equilibria in the range pH 4.23–5.35 in the presence of excess phenanthroline (pK_a1 = 3.71±0.03, pK_a2 = 5.28± 0.07). The solution reacts quantitatively with I⁻ to produce [Fe(phen)₃]²⁺ and I₂. Only 1 but none of its hydrolytic derivatives is kinetically active. Both inner and outer sphere pathways operate. The observed rate constants show second‐order dependence on the concentration of iodide, while the dependence on [H⁺] is complex in nature. Added Cl⁻ inhibits the formation of adduct with I⁻ and thus retards the rate of inner sphere path, leading to a rate saturation at high [Cl⁻], where only the outer sphere mechanism is active. Kinetic data indicate that simultaneous presence of two I⁻ in the vicinity of diiron core is necessary for the reduction of 1 . © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 737–743, 2005     

Reaction of iron(III) with tiron in the presence of ferrozine, and determination of tiron

Tiron is oxidized by iron(III) in the presence of Ferrozine with an apparent four-electron transfer and aromatic ring opening. The apparent molar absorptivity referred to the Tiron in the reaction corresponds to approximately 1.12 x 10(5) l.mole(-1).cm(-1).     

碱性介质中二过碘酸合铜(III)配离子氧化四氢糠醇的动力学及机理

本文采用分光光度法研究了二过碘酸合铜(III)配离子在碱性介质中氧化四氢糠醇的动力学及机理. 结果表明反应对[Cu(III)]是一级, 对四氢糠醇是1.3级. 反应速率随体系中[OH^-]的增大而增大, 随过碘酸浓度的增大而减小, 反应体系加入硝酸钾盐时,速率增大, 有正盐效应. 在氮气保护下, 体系能够诱发丙烯酰胺聚合. 提出了一种含有自由基过程的反应机理, 据此导出了一个能够解释本文全部实验事实的速率方程. 求得了速率控制步骤的速率常数, 并给出了相应的活化参数.     

Kinetics of oxidation of phenanthrene by acidic hexacyanoferrate(III)

Under kinetically controlled conditions, phenanthrene is converted to 9-hydroxyphenanthrene by acid hexacyanoferrate(III) in 90% aqueous acetic acid. The value of –4.0 indicates that the reaction proceeds via the formation of a cation radical intermediate.

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(III) 9- 90%- . =–4,00, -.

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Kinetics and mechanism of oxidation of chloramphenicol by 1-chlorobenzotriazole in acidic medium

Chloramphenicol (CAP) is an antibiotic drug having a wide spectrum of activity. The kinetics of oxidation of chloramphenicol by 1-chlorobenzotriazole (CBT) in HClO₄ medium over the temperature range 293–323 K has been investigated. The reaction exhibits first-order kinetics with respect to [CBT]_o and zero-order with respect to [CAP]_o. The fractional-order dependence of rate on [H⁺] suggests complex formation between CBT and H⁺. It fails to induce polymerization of acrylonitrile under the experimental conditions employed. Activation parameters are evaluated. The observed solvent isotope effect indicates the absence of hydride transfer during oxidation. Effects of dielectric constant and ionic strength of the medium on the reaction rate have been studied. Oxidation products are identified. A suitable reaction scheme is proposed and an appropriate rate law is deduced to account for the observed kinetic data.     

Kinetics and mechanism of the oxidation of hydrazinium ion by gold(III) in hydrochloric acid medium

Summary Kinetics of the oxidation of hydrazinium ion by gold(III) have been studied spectrophotometrically in hydrochloric acid medium. The reaction is first-order with respect to both gold(III) and hydrazinium ion. Hydrogen ion inhibits the oxidation. The mechanism of the reaction is discussed.