Kinetics of cysteine autoxidation catalyzed by cobalt (II) tetrasulfophalocyanine

Kinetics of cysteine (Cys) autoxidation catalyzed by cobalt (II) tetrasulfophthalocyanine (CoTSPc) has been studied by the polarographic method. Kinetic equation derived indicates that the reaction follows a mechanism involving the formation of an intermediate ternary CoTSPc (Cys) (O₂) complex that probably contains a second Cys as RS^. radical on a macrocyclic ligand.

---

(ѕ), (II) (CoTSPc). , CoTSPc (Cys) (O₂), , RS^. .

     

Solvent-free oxidation of cumene by molecular oxygen catalyzed by cobalt salen-type complexes

Co(salen)-type [where salen?=?di-(salicylal)-ethylenediimine] complexes were shown to be efficient catalysts in the oxidation of 2-phenylpropane (cumene) by dioxygen primarily to 2-phenyl-2-propanol (cumyl alcohol), 2-phenylpropene (??-methylstyrene), and 1-phenylethanone (acetophenone) applying ¹H NMR spectroscopy and gas chromatography?Cmass spectrometry (GC?CMS). The effect of substitution on the ligand was also monitored in both oxygen-absorption and the catalytic reaction. Based on these results, the trend observed for the production of ??-methylstyrene and cumyl alcohol were parallel to dioxygen uptake by the catalyst in neat cumene, while acetophenone productions obeyed a non-linear trend. The best selectivity for the reaction in terms of acetophenone production was observed for the complex with the least oxygen-absorption feature. The intermediate of the reaction, LCo(III)-OOcumyl (where L?=?salen) complex, was synthesized and characterized by IR, ¹H NMR spectroscopy as well as elemental analysis, and its reactivity in the present catalytic reaction was also studied. A series of experiments were performed to propose a mechanism for the reaction on the basis of the product distributions in the reaction mixture.     

Kinetics of nitric oxide oxidation

Nitrogen oxides are nowadays a subject of global concern. Several types of nitrogen oxides exist in the environment: N₂O, NO, NO₂, N₂O₃, N₂O₄, N₂O₅. The abbreviation NO _x usually relates to nitric oxide NO, nitrogen dioxide NO₂, and nitrous oxide N₂O. The first two are harmful pollutants for both environment and human health, whereas the third is one of the greenhouse gases. Implementation of stringent NO _x emission regulations requires the development of new NO _x removal technologies from exhaust gases. One of many proposals for NO _x emission reduction is the application of an oxidizing agent which would transform NO _x to higher nitrogen oxides with higher solubility in water. The main objective of the paper was to present the rate constant of nitric oxide oxidation, determined in our studies.     

Kinetics of the molybdate catalyzed oxidation of iodide by hydrogen peroxide

The kinetics of the oxidation of iodide by hydrogen peroxide catalyzed by acidic molybdate have been studied by a spectrophotometric stopped-flow method. The results are interpreted in terms of the mechanism and the implied rate law where [mol] is total analytical concentration of molybdate. The values obtained for the rate and equilibrium constants are k₄ = (3.3 ± 1) × 10² 1./mole · s, K₁ = (1.2 ± 0.6) × 10⁴ 1./mole, K₂ = (1.3 ± 0.7) × 10³ 1./mole, and K₃ = (4 ± 3) × 10² 1./mole at 298°K.     

对二甲苯氧化产物的高效液相色谱分析

对甲基苯甲酸是重要的化工原料与药物合成中间体。以过渡金属络合物催化剂氧化对二甲苯合成对甲基苯甲酸,粗产品或精制产品中均或多或少地含有深度氧化副产物对苯二甲酸与对羧基苯甲醛等。分析测定这些副产物对控制氧化反应条件与优化粗产品的精制过程、提高目标产物选     

Kinetics of Ag(I) catalyzed oxidation of dioxane by peroxydisulfate

Kinetic results of Ag(I) catalyzed oxidation of dioxane by peroxydisulfate ion, followed iodometrically, are discussed. Glyoxal has been indentified as the major oxidation product. On the basis of kinetic studies and product formed a radical mechanism is proposed.

---

, Ag(I), . . .

     

Kinetics of autoxidation of potassium O-butyl dithiocarbonate catalyzed by cobalt(II) tetrasulfophthalocyanine

Autoxidation kinetics of potassium O-butyl dithio-carbonate catalyzed by cobalt(II) tetrasulfophthalocyanine has been studied polarographically. The reaction follows two parallel pathways of zero and first order with respect to dioxygen, each being a Michaelis function of the substrate concentration. On the basic of data obtained and those reported previously for cysteine autoxidation, a general reaction mechanism is suggested.

---

O- , - (II). , , . , , .

     

n-Octane liquid-phase oxidation catalyzed by cobalt salts: Overall kinetic and product distribution

n-Octane liquid-phase oxidation with oxygen-nitrogen mixtures homogeneously catalyzed by cobalt palmitate has been studied. The temperature (135 °C, 140 °C and 145 °C), the oxygen partial pressure (0.1 atm, 0.2 atm and 0.4 atm) and the catalyst concentration (1 ppm, 10 ppm and 100 ppm of Co) have been varied. An overall kinetic equation for the disappearance of hydrocarbon was determined and the influence of the experimental variables on the product distribution was analyzed. The ketone and alcohol isomers and acid distributions are also discussed.     

Efficient oxidation of ethylbenzene catalyzed by cobalt zeolitic imidazolate framework ZIF-67 and NHPI

Efficient catalytic oxidation of ethylbenzene to acetophenone was realized using the catalytic system of cobalt zeolitic imidazolate framework ZIF-67/N-hydroxyphthalimide （NHPI） under mild conditions. 95.2% conversion of ethylbenzene with 90.3% selectivity to acetophenone could be obtained at 373 K under 0.3 MPa 02 for 9 h. The results show that there exists synergetic effect between ZIF-67 and NHPI. 1-Phenylethyl hydroperoxide （PEHP） was generated via a radical process involving the hydrogen abstraction from ethylbenzene by phthalimide N-oxyl, and subsequently effectively decomposed to acetophenone by ZIF-67.     

Enhanced enantioselective oxidation of olefins catalyzed by Mn-porphyrin immobilized on graphene oxide

An efficient enantioselective heterogeneous catalyst, GO-[Mn(TPyP)tart], was prepared by covalent attachment of Mn(III) complex of H₂TPyP via the propyl linkage to graphene oxide (GO) nanosheet and using chiral tartrate counter ion. The catalyst was characterized by Fourier transform infrared (FT-IR), diffuse reflectance ultraviolet–visible (DR UV–Vis) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and thermogravimetric analysis (TGA). The graphene-supported Mn-porphyrin showed higher activity for the enantioselective epoxidation of unfunctionalized olefins with molecular oxygen in the presence of isobutyraldehyde. It could be recovered easily and reused in asymmetric oxidation of styrene precursor in a five-step sequence without any considerable loss of its catalytic activity and selectivity. The obtained optically epoxide selectivities were achieved in 86% to 100%.     

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.

---

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

     

Hydroesterification of ethylene oxide catalyzed by 1-butyl-3-methylimidazolium cobalt tetracarbonyl ionic liquid

In this paper, functional ionic liquid 1-butyl-3-methylimidazolium cobalt tetracarbonyl [Bmim][Co(CO)₄] is prepared in a metathesis reaction between [Bmim]Cl and KCo(CO)₄. The structure of [Bmim]⁺ is illustrated by ¹H NMR, while [Co(CO)₄]⁻ is confirmed by IR(ν_CO) spectrum. Methyl 3-hydroxypropionate(3-HPM), an intermediate to 1,3-propanediol (1,3-PDO), can be prepared in high yield by hydroesterification of ethylene oxide in the presence of a [Bmim][Co(CO)₄] catalyst. Under a pressure of 3.7 MPa and at a temperature of 75 °C, the yield of 3-HPM can reach 90.8% in 10 h. Even after the catalyst is recycled three times, a yield of more than 80% can be obtained. A possible reaction mechanism has also been proposed.     

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 acid catalyzed oxidation of phenol and substituted phenols by isoquinolinium bromochromate

Oxidation of phenols by isoquinolinium bromochromate (IQBC) in aqueous acetic acid leads to the formation of corresponding quinones. The reaction is first order with respect to both phenol and IQBC and catalysed by hydrogen ion. The rate of oxidation decreases with increase in dielectric constant of solvent indicating ion-dipole interaction. The rate of oxidation decreases with increase in concentration of KCl, this may be due to the formation of less reactive species by interaction of Cl⁻ and protonated IQBC. The specific rates of oxidizing phenol reaction correlate with substituents constants affording negative reaction constants. Hammett plot is found to be valid and the correlation between enthalpies and free energies of activation is reasonably linear with an isokinetic temperature of 320 K.