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1.
The kinetics of oxidation of 11 para‐ and meta‐substituted benzylamines by imidazolium fluorochromate (IFC) in different organic solvent media has been investigated in the presence of p‐toluenesulfonic acid (TsOH). The reaction was run under pseudo‐first‐order conditions. The rate of the reaction was found to be first order in IFC and found to increase with increase in [TsOH]. Solution IR studies in combination with kinetic measurements were used to get a better insight into the mechanism of the oxidation process. The product analysis was carried out using GC–MS. Various thermodynamic parameters for the oxidation have been reported and discussed along with the validity of the isokinetic relationship. The specific rate of oxidizing species benzylamines reaction (k2) correlates with Hammett's substituent constants affording positive reaction constants. The rate data failed to correlate with macroscopic solvent parameters, such as εr and ENT, while showing satisfactory correlation with Kamlet–Taft's solvatochromic parameters (α, β, and π*) which suggests that the specific solute–solvent interactions play a major role in governing the reactivity, and the observed solvent effects have been explained on the basis of solute–solvent complexation. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 362–369, 2007 相似文献
2.
The oxidation induced reactions of the common lithium battery electrolyte solvent ethylene carbonate (EC) have been investigated for EC(2) using density functional theory and for selected reaction paths using M?ller-Plesset perturbation theory (MP4). The importance of explicitly treating at least one solvent molecule interacting with EC during oxidation (removal of an electron) on the EC oxidation potential and decomposition reactions was shown by comparing oxidation of EC and EC(2). Accuracy of DFT results was evaluated by comparing with MP4 and G4 values for oxidation of EC. The polarized continuum model (PCM) was used to implicitly include the rest of the surrounding solvent. The oxidation potentials of EC(2) and EC(4) were found to be significantly lower than the intrinsic oxidation potential of an isolated EC and also lower than the oxidation potential of EC-BF(4)(-). The exothermic proton abstraction from the ethylene group of EC by the carbonyl group of another EC was responsible for the decreased oxidative stability of EC(2) and EC(4) compared to EC. The most exothermic path with the smallest barrier for EC(2) oxidation yielded CO(2) and an ethanol radical cation. The reaction paths with the higher barrier yielded oligo(ethylene carbonate) suggesting a pathway for the experimentally observed poly(ethylene carbonate) formation of EC-based electrolytes at cathode surfaces. 相似文献
3.
The oxidation of iron(II) with tert-butyl hydroperoxide was investigated in the absence of oxygen in water, methanol, and the dichloromethane—methanol solvent
mixture (φr = 2:1). The oxidation rate depends on solvent polarity; measured in the presence of SCN− at constant 0.8 mmol dm−3 HCl, the rate constant increases with the polarity decrease passing from water and methanol to the dichloromethane—methanol
solvent mixture. Further, in non-aqueous solutions at this acid concentration the rate constant was higher than the rate constant
in the presence of Cl− only. The oxidation rate measured in the [FeCl]2+ complex in dichloromethane—methanol was slow in acidic medium and increased by decreasing the acid concentration. Approaching
the physiological pH conditions the rate constant attained the value of an order of magnitude of 103 dm3 mol−1 s−1, while very little alteration of stoichiometry of the oxidation reaction was observed. The rate constant measured in the
presence of Cl− strongly depends on electrolyte concentration at concentrations less than 0.5 mmol dm−3 HCl, both in MeOH and the solvent mixture. Based on these results, a possible mechanism of the influence of solvent, acidity,
and ligand type on the rate constant is discussed. We assume that the oxidation proceeds by an inner-sphere mechanism considering
that the breakdown of the successor inner-sphere complex forming reactive alkoxyl radicals is probably the rate-limiting step.
Presented at the 20th International Conference on the Coordination and Bioinorganic Chemistry organized by the Slovak Chemical
Society, Slovak University of Technology, Comenius University, and the Slovak Academy of Sciences, Smolenice Castle, 5–10
June 2005. 相似文献
4.
The oxidation rate of 3,5-di-t-butylsalicyl alcohol by 3-methyl-10-ethyl-5-deazaisoalloxazine was found to be very sensitive to solvent effect, the rate constant in 99 vol% DMF being greater by a factor of 37 than that in 50:50 (v/v) DMF-water mixed solvent. The result suggests the importance of the aprotic nature of the reaction environment during the oxidation of alcohols by NAD+. 相似文献
5.
A. E. Meshechkina L. V. Mel’nik G. V. Rybina S. S. Srednev A. S. Shevchuk 《Russian Journal of Applied Chemistry》2012,85(4):661-665
The effect of the structure and amount of the phase-transfer catalyst (quaternary ammonium salts) and the solvent effect on cyclopentene oxidation with an aqueous hydrogen peroxide solution in the liquid-liquid two-phase system was studied. The phase-transfer catalyst and solvent ensuring high reaction rate and high selectivity with respect to target products were chosen. 相似文献
6.
Oxidation kinetics of benzaldehyde and some of its ortho- and para-monosubstituted derivatives have been studied using cetylpicolinium dichromates, a class of novel phase transfer oxidants, in dichloromethane medium. The rate of reaction is first order with respect to oxidant and fractional order with respect to the substrates. The Michaelis–Menten type oxidation was observed with respect to the substrates. Benzaldehydes are found to be oxidized to their corresponding acids. The mechanism of oxidation reaction has been suggested based on the solvent isotope effect, Hammett plot, and thermodynamic study. The solvent isotope effect (kCHCl3/kCDCl3 = 1.57) indicates the involvement of hydrogen exchange with the medium during oxidation reactions. A strong influence of specific solute–solvent interactions on the rate of the reaction is observed. Both the electron-withdrawing and electron-releasing substituents on the substrates accelerate the rate of reaction. 相似文献
7.
The oxidation of 35 monosubstituted benzaldehydes by benzyltrimethylammonium chlorobromate (BTMACB) in aqueous acetic acid leads to the formation of the corresponding benzoic acids. The reaction is first order with respect to both benzaldehyde and BTMACB. The reaction failed to induce the polymerization of acrylonitrile. There is no effect of benzyltrimethylammonium chloride or potassium bromide on the reaction rate. The oxidation of [(2)H]benzaldehyde (PhCDO) indicated the presence of a substantial kinetic isotope effect. The effect of solvent composition indicated that the reaction rate increases with an increase in the polarity of the solvent. The rates of oxidation of meta- and para-substituted benzaldehydes were correlated in terms of Charton's triparametric LDR equation, whereas the oxidation of ortho-substituted benzaldehydes was correlated with the tetraparametric LDRS equation. The oxidation of para-substituted benzaldehydes is more susceptible to the delocalization effect, whereas the oxidation of ortho-and meta-substituted compounds displayed a greater dependence on the field effect. The positive value of eta suggests the presence of an electron-deficient reaction center in the rate-determining step. The reaction is subjected to steric hindrance by the ortho substituents. 相似文献
8.
V. S. Dutka N. V. Matsyuk Yu. V. Dutka 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(1):45-50
The influence of different solvents on the oxidation reaction rate of pyridine (Py), quinoline (QN), acridine (AN), α-oxyquinoline
(OQN) and α-picolinic acid (APA) by peroxydecanoic acid (PDA) was studied. It was found that the oxidation rate grows in the
series Py < QN < AN, and the rate of the oxidation reaction of compounds containing a substituent in the α position from a
reactive center is significantly lower than for unsubstituted analogues. The effective energies of activation of the oxidation
reaction were found. It was shown that in the first stage, the reaction mechanism includes the rapid formation of an intermediate
complex nitrogen-containing compound, peroxyacid, which forms products upon decomposing in the second stage. A kinetic equation
that describes the studied process is offered. The constants of equilibrium of the intermediate complex formation (K
eq) and its decomposition constant (k
2) in acetone and benzene were calculated. It was shown that the nature of the solvent influences the numerical values of both
K
p and k
2. It was established that introduction of acetic acid (which is able to form compounds with Py) into the reaction medium slows
the rate of the oxidation process drastically. Correlation equations linking the polarity, polarizability, electrophilicity,
and basicity of solvents with the constant of the PDA oxidation reaction rate for Py were found. It was concluded that the
basicity and polarity of the solvent have a decisive influence on the oxidation reaction rate, while the polarizability and
electrophilicity of the reaction medium do not influence the oxidation reaction rate. 相似文献
9.
Yoshio Kamiya 《Journal of polymer science. Part A, Polymer chemistry》1968,6(9):2561-2572
The autoxidation of isotactic polypropylene suspended in the organic solvent was found to proceed very rapidly in the presence of cobalt salts. The rate of oxidation increases and the induction period decreases as the concentration of the cobalt is increased. The rate of oxidation depends on solvent and is quite fast in fatty acids. Polypropylene has shown a rapid decrease in molecular weight at the initial stage of oxidation, and the volatile products were mainly composed of carbon dioxide and small amount of carbon monoxide. Other oxidation products were acetic acid-soluble resinous materials, having molecular weights of 250–730, with a molar ratio of carbon to oxygen of 3.0–5.4. Atactic polypropylene, relatively stable against oxidation, was oxidized easily in the presence of cobalt and bromide ion. The difference in the rate of oxidation depending on the tacticity of polypropylene is attributed primarily to steric hindrance to the intramolecular hydrogen abstraction step. 相似文献
10.
11.
The kinetics of oxidation of several para‐substituted benzaldehydes by quinolinium chlorochromate was studied under pseudo‐first‐order conditions in different (hydrogen bond donor and hydrogen bond acceptor) neat organic solvents. The operation of nonspecific and specific solvent–solvent–solute interactions was explored by correlating the rate data with solvent parameters through correlation analysis. Both electron‐releasing and electron‐withdrawing substituents enhanced the rate and the Hammett plot showed a break in the reactivity order indicating applicability of dual mechanism. An explanation in conformity with structure and solvent effects on reactivity has been proposed. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 154–158, 2003 相似文献
12.
The efficiency of the bromide mediated benzoylperoxide oxidation of 2° alcohols to ketones was greatly improved by the addition of water. The aqueous oxidation protocol allows also the direct use of off-the-shelf benzoylperoxide reagent without an otherwise necessary and potentially dangerous drying procedure. The oxidation of cyclopentanol, cyclohexanol, 1-phenyl-ethanol and three menthol isomers occurred in good to excellent yields. The oxidation reaction tolerated N,N-dimethylacetamide (DMA) as the solvent, which resulted in a slightly lower oxidation rate than acetonitrile. Chemoselective oxidation of vicinal diols to α-hydroxy ketones did not succeed under the aqueous organic conditions employed as over-oxidation and bromination side-reactions were observed. The impact of water content, solvent, oxidant source and type of alcohol substrates employed was investigated. 相似文献
13.
The kinetics of oxidation of Isoniazid (INH) by sodium N‐haloarenesulfonamidates, chloramine‐T (CAT), bromamine‐T (BAT), chloramine‐B (CAB), and bromamine‐B (BAB), has been studied in alkaline medium at 303 K. The oxidation reaction follows identical kinetics with a first‐order dependence on each [oxidant] and [INH] and an inverse fractional‐order on [OH−:]. Addition of the reaction product (p‐toluenesulfonamide or benzenesulfonamide) had no significant effect on the reaction rate. Variation of ionic strength and addition of halide ions have no influence on the rate. There is a negative effect of dielectric constant of the solvent. Studies of solvent isotope effects using D2O showed a retardation of rate in the heavier medium. The reaction was studied at different temperatures, and activation parameters have been computed from the Arrhenius and Eyring plots. Isonicotinic acid was identified as the oxidation product by GC‐MS. A two‐pathway mechanism is pro‐posed in which RNHX and the anion RNX− interact with the substrate in the rate‐limiting steps. The mechanism proposed and the derived rate laws are consistent with the observed kinetics. The rate of oxidation of INH increases in the order: BAT > BAB > CAT > CAB. This effect is mainly due to electronic factors. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 221–230, 2000 相似文献
14.
Carbonylruthenium tetrakis(pentafluorophenyl)porphyrin Ru(TPFPP)(CO) was utilized for the aerobic oxidation of alcohols. The in situ activation of the catalyst with mCPBA provided a species capable of catalyzing the oxidation of alcohols with molecular oxygen. The choice of solvent and additive was crucial to obtaining high activity and selectivity. Secondary aromatic alcohols were oxidized in the presence of the ruthenium porphyrin and tetrabutyl ammonium hydroxide in the solvent bromotrichloromethane, enabling high yields to be achieved (up to 99%). Alternatively, alcohols could be oxidized in perfluoro(methyldecalin) with the ruthenium porphyrin at higher temperatures (140 degrees C) and elevated oxygen pressures (50 psi). 相似文献
15.
Chen Z Concepcion JJ Luo H Hull JF Paul A Meyer TJ 《Journal of the American Chemical Society》2010,132(50):17670-17673
The complex [Ru(Mebimpy)(bpy)(OH(2))](2+) [Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy = 2,2'-bipyridine] and its 4,4'-(PO(3)H(2)CH(2))(2)bpy derivative on oxide electrodes are water oxidation catalysts in propylene carbonate and 2,2,2-trifluoroethanol (TFE) to which water has been added as a limiting reagent. The rate of water oxidation is greatly enhanced relative to that with water as the solvent and occurs by a pathway that is first-order in H(2)O; an additional pathway that is first-order in acetate appears when TFE is used as the solvent. 相似文献
16.
17.
N. M. Alpatova E. V. Ovsyannikova F. Jonas S. Kirchmeyer E. Yu. Pisarevskaya M. Yu. Grosheva 《Russian Journal of Electrochemistry》2002,38(6):576-582
Electrochemical oxidation and reduction of poly(3,4-ethylenedioxythiophene) in solvents of different donor capabilities is studied by cyclic voltammetry. The reversibility of the anodic process is dependent on the solvent viscosity. The polymer's anodic oxidation is presumably limited by the rate of removal of solvent molecules released during the desolvation of anions-dopants of the polymer matrix. The reversibility of the polymer's cathodic reduction improves with increasing donor capability of the solvent. A residual charge of both signs discovered in the polymer points to its chemical heterogeneity. An in-principle feasibility of copolymerization of 3,4-ethylenedioxythiophene and bithiophene is shown. 相似文献
18.
以过氧化叔丁醇为氧化剂,以钴(Ⅱ)与含N配体为催化体系催化氧化2-乙基-3-甲基吡嗪(EMP),提出一种具有放大应用前景的2-乙酰基-3-甲基吡嗪绿色制备方法.考察了过渡金属催化剂的种类、配体种类、溶剂、温度等反应条件对催化氧化过程的影响,在最优反应条件下EMP转化率可达58.8%, 2-乙酰基-3-甲基吡嗪(AMP)选择性92.2%.研究了该反应体系催化氧化EMP的反应机理,建立了该反应的拟均相反应动力学模型.在以上实验基础上,对该反应体系进行了放大实验研究,结果表明该新方法具有较好的工业放大前景,但反应温度的控制是放大过程的关键因素. 相似文献
19.
20.
The kinetics of the oxidation of diazepam (DZ) by Chloramine-B (CAB) has been studied in aqueous hydrochloric acid medium. The oxidation reaction follows the rate law: The dependence of the reaction rate on temperature is studied and activation parameters for the rate-determining step are evaluated. The dielectric constant of the medium has a small effect on the rate. Ionic strength and the reaction product benzenesulfonamide have no effect on the reaction rate. The solvent isotope effect is studied. A probable mechanism for the observed kinetic data is proposed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 605–611, 1998 相似文献