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91.
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93.
Under steady-state conditions, the current equations of the second-order EC, ECE and DISPI reactions at microdisk, microspherical and microring electrodes are derived with the aid of the concept of the reaction layer. The conditions under which these equations would be valid are also discussed. Using these equations, methods to determine the kinetic parameters for the second-order EC, ECE and DISPI reactions are presented. The reduction of 2,6-diphenyl-pyrylium cation and oxidation of triphenylamine were investigated as examples of the second-order EC and ECE reactions. 相似文献
94.
WeiHuaHAN HaoRanLI 《中国化学快报》2005,16(1):15-16
(-)-cis-1, 3-Dibenzyl-hexahydrofuro[3, 4-d]imidazole-2, 4-dione was prepared by a new synthesis method from meso dicarboxylic acid and dehydroabietylamine by asymmetric reduction in good yield with up to 91.6% e.e. value. 相似文献
95.
Jia Hui Xu Ting Ting Zhuang Yi Cao Dr. Jing Yang Jing Jia Wen Zheng Ying Wu Dr. Chun Fang Zhou Dr. Li Huang Ying Wang Prof. Dr. Ming Bo Yue Dr. Jian Hua Zhu Prof. Dr. 《化学:亚洲杂志》2007,2(8):996-1006
Copper oxide was incorporated into MCM‐41 by a one‐pot synthesis under acidic conditions to prepare a new mesoporous nitrosamines trap for protection of the environment. The resulting composites were characterized by XRD, N2 adsorption–desorption, and H2 temperature‐programmed reduction techniques, and their adsorption capabilities were assessed in the gaseous adsorption of N‐nitrosopyrrolidine (NPYR). The adsorption isotherms were consistent with the Freundlich equation. The copper salt was deposited onto MCM‐41 during the evaporation stage and was fixed on the host in the calcination process that followed. MCM‐41 was able to capture NPYR in air below 373 K but not at 453 K. Loading of copper oxide on MCM‐41 greatly improved its adsorption capability at elevated temperatures. The influence of the incorporation of copper into MCM‐41 samples and the adsorption behavior of these samples are discussed in detail. 相似文献
96.
N—(β—羧丙酰基)异鲁米诺的电致化学发光行为及其机理探讨 总被引:1,自引:0,他引:1
本进行了N-(β-羧丙酰基)异鲁米诺的电致化学发光行为的研究。采用正矩形液脉冲电压,在KOH-KCl-H2O2-(pH11.6)介质中,N-(β-羧丙酰基)异鲁米诺测定的线性范围为4.0×10^-10 ̄7.0×10^-8mol/L,检出限为2.0×10^-10mol/L。本对此体系的电致化学发光机理进行了探讨。 相似文献
97.
The dinuclear copper(II) cryptate [Cu2L](ClO4)4 (1) cleaves the C-C bond of acetonitrile at room temperature to produce a cyanide bridged complex of [Cu2L(CN)](ClO4)3.2CH3CN.4H2O (2). The cleavage mechanism is presented on the basis of the results of the crystal structure of 2, electronic absorption spectra, ESI-MS spectroscopy, and GC spectra of 1, respectively. 相似文献
98.
Mezer A Friedman R Noivirt O Nachliel E Gutman M 《The journal of physical chemistry. B》2005,109(22):11379-11388
The surface of a protein, or a membrane, is spotted with a multitude of proton-binding sites, some of which are only a few angstroms apart. When a proton is released from one site, it propagates through the water by a random walk under the bias of the local electrostatic potential determined by the distribution of the charges on the protein. Some of the released protons disperse into the bulk, but during the first few nanoseconds, the released protons can be trapped by encounter with nearby acceptor sites. This process resembles a scenario which corresponds with the time-dependent Debye-Smoluchowski equation. In the present study, we investigated the mechanism of proton transfer between sites that are only a few angstroms apart, using as a model the proton exchange between sites on a small molecule, fluorescein, having two, spectrally distinguishable, proton-binding sites. The first site is the oxyanion on the chromophore ring structure. The second site is the carboxylate moiety on the benzene ring of the molecule. Through our experiments, we were able to reconstruct the state of protonation at each site and the velocity of proton transfer between them. The fluorescein was protonated by a few nanosecond long proton pulse under specific conditions that ensured that the dye molecules would be protonated only by a single proton. The dynamics of the protonation of the chromophore were measured under varying initial conditions (temperature, ionic strength, and different solvents (H(2)O or D(2)O)), and the velocity of the proton transfer between the two sites was extracted from the overall global analysis of the signals. The dynamics of the proton transfer between the two proton-binding sites of the fluorescein indicated that the efficiency of the site-to-site proton transfer is very sensitive to the presence of the screening electrolyte and has a very high kinetic isotope effect (KIE = 55). These two parameters clearly distinguish the mechanism from proton diffusion in bulk water. The activation energy of the reaction (E(a) = 11 kcal mol(-1)) is also significantly higher than the activation energy for proton dissociation in bulk water (E(a) approximately 2.5 kcal mol(-1)). These observations are discussed with respect to the effect of the solute on the water molecules located within the solvation layer. 相似文献
99.
Poly(acrylp-aminobenzenesulfonamideamidine-p-aminobenzenesulfonylamide) chelating fiber containing "S", "N", and "O" elements was synthesized from polyacrylonitrile fiber and p-aminobenzene sulfonamide and used to enrich and separate trace Bi(III), Hg(III), Au(III), and Pd(IV) ions from wastewater and ore sample solution. The enrichment acidity, flow rate, elution conditions, reuse, interference ions, saturated adsorption capacity, constant of adsorption rate, analytical accuracy, and actual samples on chelating fiber were investigated by means of inductively coupled plasma optical emission spectrometry (ICP-OES) with satisfactory results. Solutions of 100 ng mL–1 of Bi(III), Hg(III), Au(III), and Pd(IV) ions can be enriched quantitatively by this chelating fiber at a rate of 1.0 mL min–1 at pH 4 and desorbed quantitatively with 20 mL of 0.25 M HCl and 2% CS(NH2)2 solution at 50 °C (with recovery 97%). When the chelating fiber was reused for 20 times, the recoveries of the analyzed ions enriched by the fiber were still over 95% (except for Hg(III)). One thousand-fold excesses of Mn2+, Ca2+, Zn2+, Mg2+, Fe3+, Cu2+, Ni2+, Al3+, and Ba2+ ions and thousands-fold excesses of Na+ and K+ cause little interference in the pre-concentration and determination of the analyzed ions. The saturated adsorption capacity of Bi(III), Hg(III), Au(III), and Pd(IV) was 4.850×10–4, 3.235×10–4, 2.807×10–4, and 3.386×10–4 mol g–1, respectively. The constants of adsorption rate were 0.409 min–1 for Bi, 0.122 min–1 for Hg, 0.039 min–1 for Au, and 0.080 min–1 for Pd. The relative standard deviations (RSDs) for the enrichment and determination of 10 ng mL–1 Bi(III), Hg(III), Au(III), and Pd(IV) were lower than 2.3%. The results obtained for these ions in actual samples by this method were basically in agreement with the given values with average errors of less than 1.0%. FT-IR spectra shows that the existence of –SO2–Ar, –H2N–Ar, O=C–NH–, HN=C–NH–, and –HN–SO2 functional groups are verified in the chelating fiber. From the FT-IR spectroscopy, we can see that Hg(III), Au(III), and Pd(IV) are mainly combined with nitrogen and sulfur (or oxygen), and Bi(III) is mainly combined with nitrogen (or oxygen) of the groups to form a chelating complex. 相似文献
100.
The interaction of fluorocarbon containing hydrophobically modified polyelectrolyte(FMPAANa) with two kinds of nonionic surfactants(hydrogenated and fluorinated)in a semidilute (0.5wt%) aqueous solution had been studied by rheological measurements,Association behavior was found in both systems.The hydrophobic interaction of FMPAANa with fluorinated surfactant(FC171) is much stronger than that with hydrogenated surfactant(NP7.5) at low surfactoant concentrations.The interaction is strengthened by surfactants being added for the density of active junctions increased.Whereas distinct phenomena for FC171 and NP7.5 start to be found as the surfactants added over their respective certain concentration.The interaction of polyelectrolyte with fluorinated surfactant increases dramatical ly while that with hydrogenated surfactant decreases. 相似文献