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1.
The new compound, Na[(Mo2
VO4)(pte)(OMe)(MeOH)2] (pte = anion of 6-acetonylisoxanthopterin), has been prepared using the redox non-innocent title ligand in MeOH–H2O, and characterized by elemental analysis and physico-chemical methods including e.s.m.s., i.r., u.v.–vis. and 1H-n.m.r. spectra. Rate constants data (1.4 × 10–3 s–1 at 300 K) for its oxygen atom transfer with dimethyl sulphoxide tally with those of synthetic analogue systems reported earlier by different authors. The negative activation entropy (–206.3 J mol–1 deg–1) is consistent with an associative mechanism for this reaction. 相似文献
2.
《Journal of Molecular Catalysis #》1982,14(1):75-86
Di-μ-hydroxo-bridged di-copper(II) complexes in aprotic media exhibit chemical properties in the oxidation reaction by molecular oxygen. Three oxidation reactions can occur without a base: oxidation of aldehydes into the corresponding acids, oxidative degradation of some carbonyl compounds into their lower homologues, and oxidative dimerisation of phenol. With a base a fourth reaction is observed: the dehydrogenation of alcohols into carbonyl compounds. Ligands, solvent and substrate structure effects are discussed. 相似文献
3.
The oxidation of -terpinene by molecular oxygen is shown to occur by a radical chain mechanism involving hydroperoxy radicals. The principal molecular reaction products are H2O2 and 1-methyl-4-isopropylbenzene. The rate constants for chain propagation and chain breaking measured at 35–70°C are (liter/mol·s) lgk3 = 7.10– (6700±400)/4.57T and lgk5 = 9.80– (2700±300)/4.57T respectively.Translated from Teoreticheskaya Éksperimental'naya Khimiya, Vol. 30, No. 3, pp. 143–146, May–June, 1994The authors thank the Ukraine National Committee for the Basic Research Fund for financing this work. 相似文献
4.
Selective oxidation of ethylbenzene catalyzed by fluorinated metalloporphyrins with molecular oxygen
This paper reported the oxidation of ethylbenzene catalyzed by fluorinated metalloporphyrins under mild conditions without any additives.The results showed that the cobalt(Ⅱ)(5,10,15,20-tetrakis(pentafluorophenyl))porphyrin was the best catalyst among the fluorinated metalloporphyrins.The conversion of ethylbenzene reached 38.6%,the selectivity to acetophenone reached 94.0%,and the turnover number is 2719 under the optimal conditions. 相似文献
5.
Y. Lakshman Kumar R. Venkata Nadh P. S. Radhakrishnamurti 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2016,90(3):552-559
Role of added chloride ions on the shift of reaction pathway of oxidation of aromatic ketones (acetophenone, desoxybenzoin) by dichloroisocyanuric acid (DCICA) was studied in aqueous acetic acid—perchloric acid medium. Participation of enolic and protonated forms of ketones in the rate determining steps is manifested from zero and first orders with respect to the oxidant in absence and presence of added chloride ions, respectively. Positive and negative effects of acid and dielectric constant on the reaction rate were observed. The observations deduce plausible mechanisms involving (i) rate-determining formation of enol from the conjugate acid of the ketone (SH+) in the absence of added chloride ions and (ii) rapid formation of molecular chlorine species from HOCl (hydrolytic species of DCICA) in the presence of added chloride ions, which then interacts with SH+ in a rate-determining step prior to the rapid steps of product formation. The order of Arrhenius parameters substantiate the proposed plausible mechanisms based on order of reactants both in presence and absence of added chloride ions. 相似文献
6.
《Polyhedron》1999,18(6):857-862
The preparation, magnetic and spectroscopic properties, crystal and molecular structures of binuclear complexes of formulae [Cu2(dpyam)2(OH)2(ONO2)2] (I), [Cu2(dpyam)2(O2CH)4(OH2)].H2O (II) are described. (I) consists of pairs of copper atoms linked by two hydroxo bridges. The co-ordination geometry at each copper atom is distorted square-pyramidal, the basal plane consisting of two hydroxo oxygen atoms and two nitrogen atoms from a dpyam ligand, while the axial co-ordination sites are occupied by nitrate oxygen atoms. The copper(II) ions in (II) are also in a distorted square-pyramidal environment. They are bridged by a formate group in an anti–syn configuration from a basal position to an axial position, while another axial position is occupied by the water oxygen atom. From magnetic susceptibility measurements at room temperature, both complexes are found to exhibit antiferromagnetic interactions and some magneto-structural trends are discussed. 相似文献
7.
The coordination of the results of different works for the systematization of the structures of products previously detected in the complex samples is an important stage in the interpretation of the results of the identification of the components of complex samples of natural origin by chromatography–mass spectrometry with the low reproducibility of their mass spectra under the conditions of electrospray ionization and limited reference information. The data processing of this kind was carried out for the products of the oxidation of the most common natural flavonoid quercetin (3,5,7,3',4'-pentahydroxyflavone) by atmospheric oxygen in weakly alkaline aqueous alcohol solutions. For the correlation of peaks in chromatograms with the structures of oxidation products, their reversed-phase HPLC retention indices in the scale of reference n-alkyl phenyl ketones were determined for the first time. It was confirmed that not all of the oxidation products are stable in solution; some of them can accumulate or disappear during the storage of the samples. 相似文献
8.
In this paper, zinc tetraaminophthalocyanine (Zn-APc) was immobilized on cellulosic fiber by covalent bond to obtain a novel cellulosic fiber supported metallophthalocyanine, named Zn-TDTAPc-F. At pH 11, upon visible light irradiation for 6 h in the presence of O2, Zn-TDTAPc-F was found to be highly effective for the degradation of phenol in aqueous solution, and the degradation rate of phenol was more than 95%. HPLC was used to confirm formic acid, fumaric acid and maleic acid as its main degradation products. 相似文献
9.
Some primary alcohols were oxidized by 2,2-bipyridinium chromate (BPC) in the presence of oxalic acid and TsOH giving aldehyde as major product. The reactions were carried out in 80% MeCN-DMF (v/v) medium under varied experimental conditions. The rate depends on the first power of the concentration of BPC and fractional power on the concentrations of alcohol, oxalic acid and TsOH. 相似文献
10.
The chemiluminescence (CL) kinetics in U(IV) oxidation by atmospheric oxygen in aqueous HClO4 has been investigated. The CL quantum yield (ηCL, E/(mol U(IV))) in this reaction is 1.4 × 10?8. The elementary event generating the CL emitter, which is the electronically excited uranyl ion *(UO 2 2+ ), is electron transfer from the uranyl ion UO 2 + to the oxidizer (·OH radical). The Ag+ ion quenches CL, and the Cu2+ ion enhances CL. 相似文献
11.
Rajeswari R. Tiruveedhula Vani Parvataneni Dikshitulu S. A. Lanka 《Transition Metal Chemistry》1995,20(2):170-173
Summary The kinetics of oxidation of DL-methionine by iron(III)-2,2-bipyridyl complex in HClO4 were studied using 20%(v/v) MeOH as solvent. The order with respect to methionine and iron(III) was unity. The rate increased with increased [bipyridyl], but decreased with increased [H+]. While the reactive species of the substrate was the zwitterionic form, that of the oxidant was [Fe(bipy)2-(H2O)2]3+. At 55 °C E
a and S
for the reaction were 50.6 ± 2.5 kJ mol–1 and –111.4 ± 7.6 JK–1 mol–1, respectively.Author to whom all correspondence should be directed. 相似文献
12.
Halligudi Nirmala N. Desai Saleem M. Nandibewoor Sharanappa T. 《Transition Metal Chemistry》2001,26(1-2):28-35
The kinetics of the RuIII catalysed oxidation of L-arginine by alkaline permanganate was studied spectrophotometrically using a rapid kinetic accessory. The reaction follows a two stage process. In both the stages the reaction is first order with respect to [oxidant] and [catalyst] with an apparent less than unit order in [substrate] and [alkali]. The data suggest that oxidation proceeds via formation of a complex between the active RuIII species and L-arginine, which then reacts with one mole of permanganate in a slow step to yield a L-arginine free radical, followed by a fast step to form the products. The reaction constants involved in the mechanism were evaluated. There is a good agreement between observed and calculated rate constants under different experimental conditions for both stages of reaction. The activation parameters for the slow step were calculated and are discussed. 相似文献
13.
I. G. Kolesnik E. G. Zhizhina K. I. Matveev 《Reaction Kinetics and Catalysis Letters》1999,68(2):339-346
A new method is proposed for synthesis of 2,6-dialkyl-1,4-benzoquinones by oxidation of 2,6-dimethyl and 2,6-di-tert-butylphenols with oxygen in a two-phase “water-organic” system in the presence of P−Mo−V heteropoly acids. 相似文献
14.
The catalytic effect of MnII ions on the pseudo-first-order rate constants (k
obs) for chromic acid oxidations of malic and oxaloethanoic acids (an oxidation product of malic acid) has been studied spectrophotometrically at 25 °C. The rates show a first-order dependence on the CrVI concentration for each reductant. The order with respect to [malic acid] was found to lie between 1 and 2, and 1 for [oxaloethanoic acid]. The rate increased markedly with increasing [MnII] in both the cases. The catalytic effects of MnII have been ascribed to a one-step three-electron process in which a termolecular complex is formed between the reductant, MnII and HCrO–
4. The intermediate CrIV is ruled out; details of such a process are discussed. Mechanisms in accordance with the experimental data are proposed for the reactions. 相似文献
15.
GUO Qing-Xiang REN Tan LI Bin WANG Jun LIU You-Cheng National Laboratory of Applied Organic Chemistry Department of Chemistry Lanzhou University Lanzhou Gansu ChinaTU Tie-Cheng DONG Ji-RongLaboratory of Radiation Chemistry Shanghai Institute of Nuclear Research Chinese Academy of Sciences Shanghai China 《中国化学》1994,12(1):66-72
Electron transfer reaction between vitamin A (1) and tris(p-bromophenyl)aminium hexachloroautimonate (2) in dichloromethane (DCM) has been investigated by means of UV-VIS absorption and ESR spectroscopy. The title radical cation formed in the reaction was characterized by a new absorption band around 600 nm and a singlet unresolved ESR spectrum with g factor of 2.0038-2.0039 and line width of 20 G. Further studies indicated that ESR pattern and parameters of the radical cation generated by 7-irradiation of 1 in CFCl3 matrix at 77 K are consistent with that resulted in the chemical oxidation in DCM at ambient temperature. 相似文献
16.
Two isoforms of β-amyloid peptides, Aβ40 and Aβ42, differ from each other only in the last two amino acids, IA, at the end of Aβ42. They, however, differ significantly in their ability in inducing Alzheimer's disease (AD). The rate curves of fibril growth of Aβ40 and Aβ42 and the effects of molecular crowding have been measured in in vitro experiments. These experimental curves, on the other hand, have been fitted in terms of rate constants for elementary reaction steps using rate equation approaches. Several sets of such rate parameters have been reported in the literature. Employing a recently developed stochastic kinetic method, implemented in a browser-based simulator, popsim, we study to reveal the differences in the kinetic behaviors implied by these sets of rate parameters. In particular, the stochastic method is used to distinguish the kinetic behaviors between Aβ40 and Aβ42 isoforms. As a result, we make general comments on the usefulness of these sets of rate parameters. 相似文献
17.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1981,37(8):639-642
Raman spectra of pivalic acid in the plastic and liquid phase have been measured. The reorientational correlation times have been evaluated from the νasCH, νCO and νCC bands as a function of temperature. The reorientational correlation time corresponding to νas CH and νCC bands is τ < 10−11 s whilst for the νCO band τ = 4ps (T = 20°C). The calculated activation energy is 26 KJ mol−1. The reorientation of the carboxylic groups which may be assisted by the proton transfer along the hydrogen bonds in dimers is discussed. 相似文献
18.
《Journal of Molecular Catalysis #》1992,71(2):157-175
The activation and thermodynamic parameters corresponding to rate and equilibrium constants, respectively, for the homogeneous oxidation of the saturated substrates, cyclohexane to cyclohexanol, cyclohexanol to cis-1,3-cyclohexane diol and olefin, cyclohexene to epoxide by Ru(III)—EDTA—ascorbateO2 system were determined by measuring the various rates and equilibrium constants at four different temperatures in the range 288–313 K and μ = 0.1 M KNO3 in a 50% (V/V) mixture of 1,4-dioxane and water in acidic medium. The kinetics of the oxidation of these substrates at each particular temperature was studied as a function of the concentration, the substrates, hydrogen ion, catalyst, ascorbic acid and molecular oxygen. The orders of the reaction in cyclohexanol and cyclohexene concentrations are one, and those in cyclohexane and hydrogen ion concentration are fractional and inverse first-order, respectively. For all substrates the reaction is first order with respect to the concentrations of molecular oxygen, ascorbic acid and catalyst. The source of the oxygen atom transferred to the substrates was confirmed by 18O2 isotope studies in which the 18O was incorporated in the oxidized products. The kinetics and solvent isotope effect were studied for the oxidation of C6H12, C6D12, C6H11OH and C6D11OD. The order of the reactivity observed in the oxidation of the substrates studied is cyclohexene > cyclohexanol > cyclohexane. A comparison of the rates of oxidation of the substrates and the corresponding activation parameters with the catalytic systems Ru(III)—EDTAO2 and Ru(III)—EDTA—ascorbateH2O2 indicated that activation parameters become more favourable in the presence of ascorbic acid, where the system acts as a mono-oxygenase and the activation energies are drastically reduced. Highly negative entropies are associated with all oxygen atom transfer reactions, indicating that the oxidation process is associative in nature. 相似文献
19.
20.
Summary The kinetics of oxidation of l-ascorbic acid by the N,N-ethylenebis(salicylideneiminato) manganese(III) complex have been studied over the 4.5–9.3 pH range. An intermediate ascorbate complex was formed which had an inhibiting effect on the rate of the redox reaction. The rapid formation of this intermediate was followed using the stopped-flow technique, whereas its slow decomposition was monitored using a conventional spectrophotometer. The formation of this intermediate was strongly pH dependent. Addition of sodium perchlorate and sodium dodecyl sulphate (anionic surfactant) affected the reaction rate. A probable mechanism comprising both the intermediate formation and the overall redox reaction is discussed. 相似文献