The kinetics of reaction between permanganate and chlorine ions in acid solutions

The reaction between MnO ₄ ^? and Cl^? was studied in acid media at room temperature and ionic strength 1 M. The stoichiometric equation of the reaction has the form MnO ₄ ^? + 8H⁺ + 4Cl^? = Mn³⁺ + 2Cl₂ + 4H₂O. The reaction proceeds in two stages. At the first stage, permanganate ions are consumed to produce one Cl₂ molecule per MnO ₄ ^? ion. At the second stage, the second Cl₂ molecule and the final MnO ₄ ^? reduction product (trivalent manganese) are formed. The first stage is a reaction first-order in MnO ₄ ^? and second-order in H⁺ and Cl^?; its rate constant is (9.8 ± 0.6) × 10^?2l⁴/(mol⁴ min). An analysis of the literature data leads to a value of 18–20 kcal/mol for its activation energy.     

Chlorination and oxidation products formed from 1,2,4-trimethylbenzene in aqueous solution under the action of chlorine dioxide

Products of the reaction of 1,2,4-trimethylbenzene with chlorine dioxide in aqueous solution were studied. A scheme of 1,2,4-trimethylbenzene transformations was suggested. The influence exerted on the number of the reaction products by the ClO₂ dosage and time of its contact with the substrate was examined.     

The mechanism of permanganate oxidation of sulfides and sulfoxides

Coupled-cluster (CCSD) and density functional computations are used to investigate historically competing mechanisms for the permanganate oxidation of sulfides and sulfoxides. The calculations all lead to a mechanism of 1,3-dipolar cycloaddition of permanganate, as opposed to historical mechanisms of attack of the sulfur atom by one O or by Mn. Such a mechanism, reminiscent of ozonolysis, may prevail in most permanganate oxidations. The ab initio activation enthalpies are in reasonable agreement with the experimental data; the ab initio activation entropies are not, possibly because of problems with Eyring equation assumptions.     

Low-temperature polymerization of acrylamide under the action of molecular chlorine

Acrylamide can polymerize under the action of molecular chlorine in the temperature range 180–210 K, as evidenced by the methods of calorimetry; UV, IR, and EPR spectroscopy; and elemental analysis.     

Molecular dynamics calculation of spectral characteristics of water clusters in the presence of ozone molecules and chlorine ions

Simultaneous interaction of the (H₂O)₅₀ cluster with O₃ molecules and Cl⁻ ions was studied by the molecular dynamics method. Six O₃ molecules located near the cluster were absorbed by the aqueous aggregate, and Cl⁻ ions in turn left the zone of the interaction with the cluster. Some of Cl⁻ ions penetrated inside the formed (O₃)₆(H₂O)₅₀ cluster and come into collision with O₃ molecules that split the ozone molecule into atoms. When Cl⁻ ions were removed sufficiently far away from the cluster, the water cluster with absorbed O₃ molecules and O atoms was observed for 15.6 ps. The interaction of water molecules with Cl⁻ ions gives rise to an increase in the integral intensity of absorption and emission IR spectra, and also to an essential decrease in the analogous characteristics of the Raman spectrum in the frequency range of 0 ≤ ω ≤ 1000 cm⁻¹. The presence of Cl⁻ ions did not affect essentially the location of the main band in the IR spectra, but considerably changed the shape of the bands in the Raman spectrum.     

Delignification of deciduous wood under the action of hydrogen peroxide and ozone

Kinetic curves of the dependence of ozone specific absorption (Q _{r, sp} ) upon the ozonation of aspen wood pretreated with solutions of hydrogen peroxide of various concentrations (from 5 × 10^?4 to 2 × 10^?1 mol/L) are obtained. The water content in the samples being 56 ± 3%. The initial rate of ozone absorption and total ozone consumption (Q _inlet) are determined. Wood samples are investigated by IR and UV diffuse reflection spectroscopy. Based on the kinetics and spectral data, it is concluded that pretreating wood with a H₂O₂ solution allows the degree of delignification (DD) to be increased at a constant Q _inlet value. The DD is maximal at $ C_{H_2 O_2 } = 5 \times 10^{ - 3} $ mol/L and is 88% in contrast to a sample ozonated without H₂O₂ (DD = 85%). The role of pretreatment with hydrogen peroxide and the subsequent action of the O₃/H₂O₂ system in the process of delignification of wood is analyzed.     

Kinetics of the base-catalyzed permanganate oxidation of benzaldehyde

The kinetics of the base-catalyzed permanganate oxidation of benzaldehyde have been reexamined. The rate is proportional to the first power of the aldehyde and permanganate concentrations, and there are terms that are zero order, first order, and second order in hydroxide ion. The reaction has an isotope effect, and the effect of substituents gives rho = +1.58. The possible mechanisms for the reaction are discussed in the context of ab initio calculations at the B3P86/6-311+G and MP2/6-31G theoretical levels, and both one- and two-electron processes are possible. Benzaldehyde hydrate dianion is calculated to have a remarkably small C-H bond dissociation energy.     

Kinetics and mechanism of the permanganate oxidation of trans-crotonic acid

The kinetics and intermediates of the permanganate oxidation of trans-crotonic acid have been investigated in the pH range of 0.5–5.0 using the stoppedflow technique. The formation of manganese(III) as a short-lived intermediate has been established. The reaction is first order with respect to both MnO ₄ ^– and crotonic acid (crotonate). The resolved rate constants at 25°C are 730 and 410 M^–1 sec^–1 for the acid and the anion, respectively. The reaction mechanism is discussed.

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pH=0,5–5,0, . (III) . MnO ₄ ^– , (). 25°C 730 410 M^{–1 –1} , . .

     

Kinetics and mechanisms of the oxidation by permanganate of L-Phenylalanine

The oxidation of L-Phenylalanine by permanganate ion in aqueous phosphate buffers is autocatalized by the inorganic reaction product, which is stabilized in solution by adsorption of phosphate ions on its surface. This product is a soluble form of colloidal manganese dioxide. The rate of the noncatalytic reaction pathway is first-order in both the oxidizing and reducing agent. It is not affected by potassium chloride addition to the solution, but by phosphate addition. The rate increases with the pH of the medium. The autocatalytic pathway is first-order in both permanganate ion and colloidal manganese dioxide, (the permanganate ion according to the Langmuir isotherm). The autocatalytic rate increases with reductant concentration (follows the Langmuir adsorption isotherm). It is not affected by potassium chloride addition to the solution, whereas an increase in the phosphate concentration results in an increase in the rate with the same pH of the medium. Mechanisms consistent with the experimental data are proposed.     

The effect of pressure on the oxidation of benzhydrol by alkaline permanganate

The rate of oxidation of benzhydrol and benzhydrol-d to benzophenone by alkaline permanganate has been measured over a pH range 10 to 12.5 and pressures from 1 to 1000 bar. The pressure effect on the rate is small, Δ$\text{V}$^≠ = ?6 to ?8 cm³mol^?1. This is held to support a hydrogen atom transfer in the rate-determining step.     

Evaluation of the performance of catalysts for joint deep oxidation of hydrocarbons and carbon monoxide under the action of UHF radiation

A series of Сu–Cr–Co/Al₂O₃/Al catalysts were synthesized under conditions of both traditional heat treatment and action of UHF field, with determination of the thermal transformation properties and degree of radiation penetration into the catalyst bulk. The performance of the catalysts in joint deep oxidation of n-butane and carbon monoxide, stimulated by microwave radiation, was evaluated. The use of the generalized Harrington desirability function reflecting the whole set of definite different-dimension partial responses facilitates the visualization of the expert evaluation of the results and can be recommended for preparing heterogeneous catalysts for related reactions, stimulated by microwave radiation, and for ranking them with respect to performance.     

The determination of organic substances by the oxidation with permanganate: XVIII. The oxidation of malonic acid

The oxidation of malonic acid with permanganate was studied under various acidity conditions. Analytical procedures, based on oxidation with excess reagent in a sodium carbonate medium and titration of the oxalate or manganese dioxide formed or of unconsumed permanganate, are proposed. On the basis of successive oxidation in sodium carbonate and sulfuric acid media, a titration determination, involving complete oxidation of malonic acid to carbon dioxide and water, was developed.     

Lewis acid-activated oxidation of alcohols by permanganate

The oxidation of alcohols by KMnO(4) is greatly accelerated by various Lewis acids. Notably the rate is increased by 4 orders of magnitude in the presence of Ca(2+). The mechanisms of the oxidation of CH(3)OH and PhCH(OH)CH(3) by MnO(4)(-) and BF(3)·MnO(4)(-) have also been studied computationally by the DFT method.     

Oxidative destruction of polyolefins under stress. The action of ozone on polyethylene and polypropylene

Tensile stresses accelerate the rate of oxidation by ozone of films of polyolefins, high-density and low-density polyethylene, and isotactic polypropylene. Experiments have been performed on thin (up to 20 μm) uniaxially oriented films under constant stress σ, under conditions where the chemical kinetics rather than diffusion dominates. It is found that the oxidation rate is proportional to exp(γ′σ/RT) where γ′ is an empirical constant. The effects of unimolecular chain scission and the change of molecular polymer parameters under stress on this dependence are negligible. An analogy with the kinetics of oxidation of stressed cycloparaffins by ozone is noted. A mechanism is suggested to explain the accelerating effect of tensile deformations on chemical processes involving rehybridization of carbon atoms in the main chain from the sp³ to the sp² state. An ESR study with a stable nitroxyl radical probe revealed a change in the segmental mobility of polymer chains in the course of loading.     

Salt effect in the oxidation of iodide by permanganate

The rate of the reaction between permanganate and iodide ions had been measured in several concentrated salt solutions. There is a salt effect, which is dependent on the hydration heat of the salt present in the reaction medium.

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Kinetics and mechanism of the oxidation of acetylacetone by permanganate ion

The kinetics and mechanism of permanganate ion oxidation of acetylacetone (Acac) was studied in acidic and alkaline media. The rate constants for keto, enol, and enolate anions were determined and discussed. Delocalization of the π‐electrons of the double bond by conjugation results in a slower oxidation rate of enol than can be usually observed for unsaturated compounds. In the case of the keto form, the acid‐catalyzed nucleophilic attack of permanganate ion occurs on the carbonyl‐C atom. For enolate anion a mechanism with basis‐catalyzed electron abstraction is suggested. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 444–450, 2006     

Mechanism and kinetics of hypophosphite oxidation by permanganate ion

The kinetics of the permanganate‐hypophosphite redox reaction has been studied over a wide range of pH by using a stopped‐flow technique. It has been found that the reaction leads to the formation of phosphite and orthophosphate, and that the molar ratio of the final products depends on pH. The proposed mechanism of the process was based on the assumption that the first step in the oxidation of hypophosphite is a fast reversible reaction in which an intermediate complex (O₃MnOH₂PO₂)²⁻ is formed. The observed dependence of the reaction rate on pH was attributed to the influence of hydrogen and hydroxyl ions on the decomposition of this complex. The rate constants and the equilibrium constants of elementary reactions are given. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 737–743, 1999     

Plasma-assisted oxidative degradation of organic dyes in solution by the joint action of underwater discharge and ozone

Data on the degradation kinetics of two organic dyes in a mixture by the action of electrical underwater discharges and ozone are presented. It has been found that the rate of degradation by the to combined treatment of the both dyes with face discharge and ozone is five times the sum of degradation rates expected on the assumption of the additive effect of each of these factors.