Co(salen) catalyzed oxidation of oximes with t-butyl hydroperoxide

Co(salen) catalyzed the oxidation of oximes with t-butyl hydroperoxide to give the parent carbonyl compounds, providing a new convenient route to deoximation reaction. A plausible mechanism involves a substrate radical intermediate.

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Co() -, . . .

     

Selective oxidation with t-butyl hydroperoxide and aluminium reagents

Stereoselective epoxidation of allylic alcohols is achieved with organoaluminium peroxides. Transformation of secondary alcohols to ketones with same reagents is also disclosed.     

Palladium-catalyzed allylic oxidation of olefins by t-butyl hydroperoxide and tellurium(IV) oxide

Treatment of several cyclic olefins, β-pinene, allylbenzene, and estragole with palladium(II) salt in acetic acid in the presence of t-butyl hydroperoxide and tellurium(IV) oxide afforded mainly the corresponding allylic acetates. The reaction proceeded catalytically with palladium(II) salt, t-BuOOH working as a reoxidizing agent.     

Ruthenium-catalyzed oxidation of alcohols and catechols using t-butyl hydroperoxide

Ruthenium complexes catalyze the oxidation of alcohols to the corresponding ketones or aldehydes when t-BuOOH (70% aq.) is used as an oxidant. The reactions proceed at room temperature to give the products in excellent to fairly good yields. Among the transition metal catalysts used, dichlorotris(triphenylphosphine)ruthenium (RuCl₂(PPh₃)₃) showed the highest catalytic activity. 3,5-Di-t-butylcatechol and 4-t-butylcatechol are also effectively oxidized to the corresponding 1,2-benzoquinones in the presence of a catalytic amount of RuCl₂(PPh₃)₃ at room temperature with 1.1 equiv. of t-BuOOH, in quantitative yields. Hydrogen peroxide (30% aq.) can also be employed as an oxidant to give 1,2-benzoquinones in excellent yields.     

The kinetics and mechanism of oxidation of hexacyanoferrate(II) by periodate ion in highly alkaline aqueous medium

The oxidation of hexacyanoferrate(II) by periodate ion has been studied spectrophotometrically by registering an increase in absorbance at 420 nm (λ_max of yellow colored [Fe(CN)₆ ^3?] complex under pseudo first-order conditions by taking excess of [IO₄ ^?] over [Fe(CN)₆ ^4?]. The reaction conditions were: pH = 9.5 ± 0.02, I = 0.1 M (NaCl) and Temp. = 25 ± 0.1 °C. The reaction exhibited first-order dependence on each [IO₄ ^?] and [Fe(CN)₆ ^4?]. The effects of variations of pH, ionic strength and temperature were also studied. The experimental observations revealed that the periodate ion exists in its protonated forms viz. [H₂IO₆]^3? and [H₃IO₆]^2? while [Fe(CN)₆]^4? is present in its deprotonated form throughout the pH region selected for the present study. It has also been observed that deprotonated form of [Fe(CN)₆ ^4?] and protonated forms of periodate ion are the most reactive species towards oxidation of [Fe(CN)₆ ^4?]. The repetitive spectral scan is provided as an evidence to prove the conversion of [Fe(CN)₆ ^4?] to [Fe(CN)₆ ^3?] in the present reaction. The activation parameters have also been computed using the Eyring’s plot and found to be, ΔH? = 51.53 ± 0.06 kJ mol^?1, ΔS? = ?97.12 ± 1.57 J K^?1 mol^?1 and provided in support of a most plausible mechanistic scheme for the reaction under study.     

过氧化叔丁醇在钼催化剂下对咔唑的催化氧化研究

以油溶性过氧化叔丁醇(TBHP)为氧化剂,采用钼(Ⅵ)类催化剂,对油品中性质稳定的氮化物-咔唑进行了催化氧化研究。考察了钼催化剂及其载体对咔唑氧化的影响。结果表明,在无负载条件下,乙酰丙酮钼(MoO2(acac)2)的催化活性略高于三氧化钼(MoO3);经弱酸性树脂(D113)负载后,MoO3催化活性显著提高;三种载体(Al2O3、树脂D113和树脂D751)均能提高钼催化剂的活性,使咔唑转化率达到65%以上,其中MoO3/Al2O3催化活性最高。杂金属Ni和Co的加入导致MoO3/Al2O3催化活性降低。其次,进行了氧化反应选择性研究,实验发现在反应液中含有二苯并噻吩时,TBHP/MoO3/D113能优先氧化咔唑;而TBHP/MoO3/D751对咔唑和二苯并噻吩具有近似的氧化活性。最后根据光谱数据对咔唑系列产物的结构进行了初步推测。     

Influence of surface oxygen groups on V(II) oxidation reaction kinetics

The role of surface oxygen groups on the kinetics of the V(II) oxidation reaction was studied on modified glassy carbon (GC) electrodes by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The reaction was found to be sensitive to the presence of oxygen groups on the electrode surface. Higher O/C ratios determined by X-ray photoelectron spectroscopy (XPS) corresponded to higher reactivities and lower charge transfer resistances measured in a 1 M V(II) electrolyte. The stability of an oxidised GC surface was also investigated in a 1 M V(II) electrolyte by potential holding and cycling experiments. It was found that after holding and cycling to successively more negative potentials up to − 0.8 V/RHE, the electrode surface lost its initial reactivity.     

Regularities of the formation of iron(III) nanocrystalline particles during the oxidation of iron(II) compounds in a neutral medium

The regularities of the formation of iron(III) oxide hydroxides as nanocrystalline particles via oxidation of iron(II) compounds in a near-neutral pH region were studied by potentiometric titration, electron microscopy, chemical analysis, and X-ray diffraction. The oxidation process comprises two steps. The first step produces Fe(II)-Fe(III) hydroxo salts having a “green rust” structure in the form of nanocrystalline particles shaped as hexagons. The second step produces anisotropic nanocrystalline particles of iron(III) oxide hydroxides via the dissolution-oxidation-precipitation mechanism and via solid-phase oxidation. The oxidation of chlorine-containing suspensions helps the formation of single-phase nanocrystalline lepidocrocite, while oxidation in the presence of sulfate ions yields nanocrystalline goethite.     

Mechanism and kinetics of the vanadium-catalyzed o-dianisidine—t-butyl hydroperoxide reaction in non-aqueous media

The vanadium-catalyzed oxidation of o-dianisidine by t-butyl hydroperoxide is studied for the determination of trace vanadium in non-aqueous media. In acetonitrile, vanadium acts as a one-eletron mediator between the reductant and oxidant. Mechanistic studies, based on e.p.r. spectrometry and visible spectrophotometry, show that the hydroperoxide oxidizes vanadium(IV) via a radical mecahnism. The kinetics of V(IV) oxidation are investigated and a rate equation is proposed. Oxidation of o-dianisidine by the vanadium(V) formed in a one-electron step with formation of the o-dianisidine radical completes the catalytic cycle, as shown by spectroelectrochemical measurements. The radical reacts further with excess of t-butyl hydroperoxide to form the diimine, which may be used for sensitive spectrophotometric monitoring of the indicator reaction at 450 nm.     

The oxidation of iron (II) sulphide

Journal of Thermal Analysis and Calorimetry - The oxidation in air and oxygen of iron (II) sulphide Fe1?x S was studied using TG, DTA, X-Ray powder photography and chemical analysis. A...     

Copper(II) and iron(II) ion sensing with semiconducting polymer dots

This communication describes a simple platform that employs carboxyl functionalized semiconducting polymer dots as a fluorescent probe for sensitive ratiometric Cu(2+) and Fe(2+) detection, in which the sensing mechanism is based on aggregation-induced fluorescence quenching.     

Metal catalysis in oxidation by peroxides part 14. Kinetics and mechanism of titanium-catalyzed oxidation of sulphides with t-butyl hydroperoxide

The oxidation of di-n-butylsulphide, p-methylphenylmethylsulphide and p-chlorophenylmethylsulphide with t-butyl hydroperoxide in the presence of catalytic amounts of TiO(acac)₂ and Ti(OPrⁱ)₄ has been studied in toluene. The reaction affords the corresponding sulphoxides in quantitative yield. Kinetic studies indicate that the oxidation rate is first order in the hydroperoxide and catalyst whereas the dependence on substrate initial concentration is rather complex, leading to an apparent positive but fractional order. This behaviour suggests that coordination of the sulphides to Ti(IV) occurs in solution. Two alternative mechanisms, both consistent with the experimental data, the ‘electrophilic’ oxidation of the free substrate by the peroxotitanium species present in the system or the intramolecular oxygen transfer to the coordinated sulphide, are discussed.     

The kinetics of peroxydisulphate ion oxidation of glycolic acid in aqueous medium

The peroxydisulphate ion oxidation of glycolic acid has been studied kinetically under various conditions using different concentrations of reactants and of a neutral salt and at different temperatures. The reaction has been found to be first order and the thermodynamic constants have been calculated. The product, formic acid, has been identified and a probable mechamism for the reaction is proposed.     

Kinetics and mechanism of the oxidation of iron(II) ion by chlorine dioxide in aqueous solution

The mechanism by which an excess of iron(II) ion reacts with aqueous chlorine dioxide to produce iron(III) ion and chloride ion has been determined. The reaction proceeds via the formation of chlorite ion, which in turn reacts with additional iron(II) to produce the observed products. The first step of the process, the reduction of chlorine dioxide to chlorite ion, is fast compared to the subsequent reduction of chlorite by iron(II). The overall stoichiometry is The rate is independent of pH over the range from 3.5 to 7.5, but the reaction is assisted by the presence of acetate ion. Thus the rate law is given by At an ionic strength of 2.0 M and at 25°C, k_u = (3.9 ± 0.1) × 10³ L mol^?1 s^?1 and k_c = (6 ± 1) × 10⁴ L mol^?1 s^?1. The formation constant for the acetatoiron(II) complex, K_f, at an ionic strength of 2.0 M and 25°C was found to be (4.8 ± 0.8) × 10^?2 L mol^?1. The activation parameters for the reaction were determined and compared to those for iron(II) ion reacting directly with chlorite ion. At 0.1 M ionic strength, the activation parameters for the two reactions were found to be identical within experimental error. The values of ΔH? and ΔS? are 64 ± 3 kJ mol^?1 and + 40 ± 10 J K^?1 mol^?1 respectively. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 554–565, 2004     

Kinetics of oxidation of iron(II) ions with lipid hydroperoxides

One of the pathways for excessive production of free radicals is the decomposition of lipid hydroperoxides catalyzed by iron. A number of hydroperoxides of unsaturated fatty acids (LOOH), some prepared in our laboratory and others extracted from biological materials, were used to determine the rate constants of Fe²⁺ oxidation by measuring the formation rate of Fe³⁺ ions in the presence of simple unidentate ligands, chloride, and thiocyanate as the [FeCl]²⁺ and [FeNCS]²⁺ complexes, in a deoxygenated dichloromethane:methanol (2:1, v/v) mixture. The rates of Fe²⁺ oxidation with prepared LOOHs via the [FeNCS]²⁺ complex were approximately the same-the average second-order reaction rate constant was 1390 ± 340 dm³ mol⁻¹ s⁻¹; the rate constants of LOOHs from different biological materials were in the same range. The rates measured as the [FeNCS]²⁺ complex were somewhat higher than the rates measured as the [FeCl]²⁺ complex, indicating that ligands could interact in the transition state, thus affecting the disruption of the intermediate complex. Since there were no significant differences in the activation thermodynamic parameters for reactions within the reaction series of studied hydroperoxides, it was assumed that the oxidation proceeded by an inner sphere mechanism, considering that the breakdown of the successor inner sphere complex with the homolytic cleavage of peroxide bonds of hydroperoxides forming reactive alkoxyl radicals was the rate-limiting step. Based on this research, an indirect spectrophotometric method for quantitative determination of LOOH was reestimated. The microprocedure proposed for the lipid hydroperoxide assay could be applied to follow the early stages of lipid peroxidation processes in real biological samples.     

Regularities of formation of iron(III) nanocrystalline oxides and oxyhydroxides during oxidation of iron(II) compounds in an alkaline medium

Regularities of formation of nanocrystalline iron(III) oxides and oxyhydroxides via oxidation of iron(II) compounds in an alkaline pH range (pH ≥ 12) were studied using pH and E _h measurements, chemical analysis, electron microscopy, and X-ray diffraction. When the molar ratio [OH⁻]/[Fe^II] ∼ 2 (pH ∼ 12–12.5), the oxidation process yields cube-shaped magnetite Fe₃O₄ particles. An excess of an alkaline agent with an overstoichiometric concentration equal to or higher than 0.5 mol/L (pH ≥ 13.5) induces the formation of anisotropic particles of nanocrystalline goethite α-FeOOH over the entire range of the synthesis parameters studied. Reaction products (Fe₃O₄ and/or α-FeOOH) are formed immediately as the initial Fe(OH)₂ starts oxidizing by the dissolution-oxidation-precipitation mechanism near the surface of Fe(OH)₂ precursor particles. Carbonate ions considerably change the structure and shape of newly formed α-FeOOH particles.     

Effects of alkyltrimethylammonium bromide surfactants on the kinetics of the oxidation of tris(1,10-phenanthroline)iron(II) by azido-pentacyanocobaltate(III) complex

The redox reaction between tris(1,10-phenanthroline)iron(II), [Fe(phen)₃]²⁺, and azido-pentacyanocobaltate(III), [Co(CN)₅N₃]^3? was investigated in three cationic surfactants: dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB) in the presence of 0.1?M NaCl at 35°C. Second-order rate constant in the absence and presence of surfactant, k_w and k_ψ, respectively, were obtained in the concentration ranges DTAB?=?0???4.667?×?10^?4?mol?dm^?3, TTAB?=?0–9.364?×?10^?5?mol?dm^?3, CTAB?=?0???6.220?×?10^?5?mol?dm^?3. Electron transfer rate was inhibited by the surfactants with premicelllar activity. Inhibition factors, k_w/k_ψ followed the trend CTAB?>?TTAB?>?DTAB with respect to the surfactant concentrations used. The magnitudes of the binding constants obtained suggest significant electrostatic and hydrophobic interactions. Activation parameters ΔH^≠, ΔS^≠, and E_a have larger positive values in the presence of surfactants than in surfactant-free medium. The electron transfer is proposed to proceed via outer-sphere mechanism in the presence of the surfactants.