Kinetics and Mechanism of the Oxidation of Somethioacids by Benzyltrimethylammonium Tribromide

The oxidation of thioglycollic, thiolactic and thiomalic acids bybenzyltrimethylammonium tribromide proceeds through the formation of asulfenium cation in the slow step.     

Green Synthesis of Tetraalkylammonium Tribromide using Cerium(IV) Ammonium Nitrate (CAN) as Oxidant

Cerium(IV) ammonium nitrate (CAN) mediates oxidation of tetraalkylammonium bromide to tetraalkylammonium tribromide in greener reaction conditions using water as solvent. The procedure is simple, convenient, and environmentally benign for the synthesis of tetraalkylammonium tribromide with great yields.     

Kinetics and mechanism of the oxidation of some diols by benzyltrimethylammoniumtribromide

The kinetics of oxidation of five vicinal and four non-vicinal diols, and two of their monoethers by benzyltrimethylammonium tribromide (BTMAB) have been studied in 3:7 (v/v) acetic acid-water mixture. The vicinal diols yield the carbonyl compounds arising out of the glycol bond fission while the other diols give the hydroxycarbonyl compounds. The reaction is first-order with respect to BTMAB. Michaelis-Menten type kinetics is observed with respect to diol. Addition of benzyltrimethylammonium chloride does not affect the rate. Tribromide ion is postulated to be the reactive oxidizing species. Oxidation of [1,1,2,2-²H₄] ethanediol shows the absence of a kinetic isotope effect. The reaction exhibits substantial solvent isotope effect. A mechanism involving a glycol-bond fission has been proposed for the oxidation of the vicinal diols. The other diols are oxidized by a hydride ion transfer to the oxidant, as are the monohydric alcohols.     

Kinetics of Oxidation of Phosphinic, Phenylphosphinic and Phosphorous Acid by Benzyltrimethylammonium Chlorobromate

The oxidation of lower phosphorus oxyacids by benzyltrimethylammonium chlorobromate (BTMACB) proceeds by a mechanism involving a hydride-ion transfer from oxyacids to the oxidant in the rate-determining step.     

Paths and Mechanism for the Oxidation of Alkanes,Alkenes, and Arenes by Peroxynitrous Acid

The bell-shaped relations between the rate constants for the oxidation of hydrocarbons by peroxynitrous acid (HOONO) and the ratio of the volumes of the aqueous and gas phases in the reactor are explained quantitatively on the assumption that the HOONO and the substrate are distributed between the gas and the solution and that OH radicals are formed in the two phases and interact with the hydrocarbon. The distribution coefficient of the HOONO between the gas and aqueous phases is determined [ = (0.4-2)·10^–6].     

Free-radical-mediated oxidation of ascorbic acid by peroxomonosulphate

The kinetics of the oxidation of ascorbic acid (AH₂) by peroxomonosulphate (PMS) were determined in aqueous medium in acidic (pH 4.4), neutral (pH 7.0) and alkaline (pH 9.0) conditions over the temperature range 13-28°C. The reactions were found to obey total second-order kinetics, first-order each with respect to peroxomonosulphate and ascorbic acid concentration, obeying-d[AH₂]/dt = k ₂[PMS][AH₂]. Dehydroascorbic acid was detected as the product of the reaction. The stoichiometry of the reaction, [peroxomonosulphate]/[ascorbicacid] = 1 : 1, indicated the absence of self-decomposition of peroxomonosulphate. The influence of neutral salt (NaClO₄) was found to increase the reaction rate. Evidence for the formation of radical intermediates was obtained. A mechanism involving the formation of hydroxyl, sulphate and ascorbate free radicals as intermediates is proposed. The rate and activation parameters were evaluated to substantiate the mechanism proposed. A comparison is made with the corresponding reactions of the similar peroxides, S₂O₈ ^2- and P₂O₈ ^4-.     

Kinetics and mechanism of oxidation of thiocarbohydrazide in the free state and in its metal complex and thiocarbohydrazone by chloramine-T and dichloramine-T

Kinetics of oxidation of thiocarbohydrazide (TCH) in the free state and as its metal complex, and as a hydrazone by chloramine-T (CAT) in aqueous HClO₄ medium, and by dichloramine-T (DCT) in 1:1 (v/v) water-methanol medium in the presence of HClO₄ have been studied. Rates of oxidation of TCH in the free state and in metal complex by CAT were determined. The rate law for the oxidation of TCH at high [H⁺ ] and for complex oxidations were identical to that for CAT oxidations. The conversion of TCH into its hydrazone changed the order in [H⁺] from a positive to a negative value, probably signalling the change of reaction site. The rate law for oxidation under these conditions was determined. Addition of the reduced product of the oxidants had no effect on the rate of oxidations. Variation in ionic strength of the medium had little positive effect, while decrease in dielectric constant of the medium decreased the rate in both the oxidations. Oxidation processes generally follow a Michaelis-Menten type of mechanism. Constants of the rate limiting steps have been calculated at different temperatures and these constants have been used to calculate the activation parameters from the Arrhenius plots. The proposed mechanisms are supported by investigations with HOC1 under identical reaction conditions. Metal complexation of the substrate decreased the reactivity, while conversion of TCH into its hydrazone changed the rate dependence on [H⁺].     

Heat release kinetics in the reaction of decane with nitric acid

The kinetics of the reaction of decane with nitric acid (25.07–75.53 %) at 57.8 to 119 °C in an acid-decane-gas triphasic system was studied. The main contribution to the rate of heat release is made by the oxidation of decane with nitrogen dioxide in the organic phase proceedingvia the mechanism of a degenerate branched-chain reaction. Nitration plays the role of a chain termination reaction. The acid phase is the source of NO₂, whose content increases with oxidation. The equilibrium of the nitrogen dioxide distribution in the triphasic system was analyzed. The kinetic law of the reaction, the dependences of the reaction constants of the initial and catalytic stages on temperature and the acid phase composition were determined. The results allow one to calculate the rate of heat release in the decane-HNO₃ system under any conditions of the process.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1986–1991, August, 1996.     

三溴化三乙基苄铵对于苯偶姻的氧化反应

作者前曾报道,三溴化三乙基苄铵(PhCH_2Et_3NBr_3~-,TEBABr_3,1)和三碘化三乙基苄铵(TEBAL_3)能作为有效的溴代和碘代试剂而与芳胺反应,以高产率生成多溴代和多碘代芳胺。在进一步对TEBABr_3在有机合成     

CsBr与SmBr3在氢溴酸介质中反应的相化学

由于稀碱稀土卤化物特殊的材料性能，正日益受到各国科学家的关注［‘－3］．动年代初，M：y：：提出了下述4种类型卤化物A’RE？X7（1：2型）、AIREyXgta：2型）、AIRE”X6ta：l型）及AgRE”X。（2：l型）的合成方法（A为碱金属）分析Meyer等人的合成方法网；发现其初始反应是