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991.
1 INTRODUCTION Halide fluxes are excellent media for growing single crystals of chalcogenides[1~5]. On our research in the Ln-Cu-Zn-Se system to find new phases and to search for potential infrared ceramic materials, two new compounds, KHo2CuSe4 and KEr2CuSe4, were synthesized from the reaction of the precursor with KCl flux[6]. In an attempt to synthesize the homologous sulfide by the same method using KBr as flux in a sealed evacuated quartz tube, single crystals of Ho4S3Si2O7 w… 相似文献
992.
The applicability of (1R,2R)-1,3-diacetoxy-1-(4-nitrophenyl)-2-propyl isothiocyanate [(R,R)-DANI] as a recently developed chiral derivatizing agent for the enantioseparation of a series of β-blockers is described. The thiourea diastereomers formed were analyzed by reversed-phase high-performance liquid chromatography, mixtures of water and methanol or acetonitrile being used for elution. Conditions of derivatizations (temperature, reagent excess and reaction time) were optimized, and the effects of organic modifiers on the retention and separation were investigated; the diastereomers could readily be baseline separated with methanol-containing mobile phases with resolutions between 1.58 and 2.72. 相似文献
993.
The adsorption of hydroxyl on Pt(1 1 1) single crystal electrodes from aqueous acidic solutions is carefully reinvestigated. The effect of small additions (10−8–10−5 M) of chloride and bisulphate anions on the OH adsorption region in perchloric acid solution has been studied. Two regions can be differentiated in the voltammetric profile, that behave differently after the addition of the foreign anion. The initial broad adsorption process is unaffected until the highest concentration is attained. However, the sharper peak at higher potentials is affected even at the lower anion concentration. Since mass transport limitations allow to discard the anion adsorption as the main process giving this peak, we propose that the two processes are due to the dissociative adsorption of two different kinds of water, that are affected by the anion in a different way. From this idea, a new model, based on the Frumkin adsorption isotherm, is proposed, which gives an excellent fit of the experimental results. 相似文献
994.
D. V. Kazakov A. I. Voloshin N. N. Kabal'nova V. V. Shereshovets V. P. Kazakov 《Russian Chemical Bulletin》1997,46(6):1089-1093
The reaction of dimethyldioxirane (1) with the RuII trisbipyridyl complex accompanied by chemiluminescence (CL) was studied. It is established that the intensity of CL and the
rate of its decay increase proportionally with the concentration of RuII. The bimolecular rate constant (k
2) of the reaction of1 with RuII was determined. The activation parameters (E
a and logA) for this reaction were calculated from the temperature dependence ofk
2. The excitation yield of RuII* (η
Ru
*
) was estimated. The quenching of RuII* by dioxirane was studied, and the bimolecular quenching constant and the coefficient of excitation regeneration were determined.
It was suggested that the catalysis of the decomposition of1 and the excitation of RuII occurvia a mechanism of chemically initiated electron exchange.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1138–1142, June, 1997. 相似文献
995.
Starting from the para‐phenylenediamine derivative HN(SiMe3)‐C6H4‐NH(SiMe3), a lithiation and subsequent borylation give [(MeO)2B]N(SiMe3)‐C6H4‐N(SiMe3)[B(OMe)2] ( 1 ), the hydridation of which yields Li2[(H3B)N(SiMe3)‐C6H4‐N(SiMe3)(BH3)] ( 2 ). Applying ZrCl4 upon 2 initiates a condensation to give the title compound [‐N(SiMe3)‐p‐C6H4‐N(SiMe3)‐BH‐]2, a hetero[3, 3]paracyclophane with two N‐B‐N chains that connect the para‐phenylene units. The product 3 crystallizes in the orthorhombic space group P212121. 相似文献
996.
Heterobimetallic Complexes with Chelate Ligands from Multidentate Amines and 1,1-Bis(diphenylphosphine)ethene By an addition reaction of bidentate amines Me2N(CH2)nNH2 (n = 2, as-4C2N; 3, as-5C2N) and vinylidene derivatives with an activated double bond CH2 = C(PPh2)2M(CO)4 (M = Cr, Mo, W) were synthesized in dichlormethane unsymmetrical chelate ligands of the type as-4C2N (or as-5C2N)PPM(CO)4. They gave with divalent salts M′Y2 (Y = ac, M′ = Cu, Ni. Y = Cl, M′ = Zn, Cd, Hg) the coloured bimetallic complexes M′Y(as-4C2N) (or as-5C2N)PPM(CO)4 which were characterized by means of IR-, UV/VIS spectroscopic and 1H, 13C and 31P NMR measurements. The molecular structures of the complexes Cuac2(as-5C2N)PPCr(CO)4, I and that of CdCl2(as-4C2N)PPCr(CO)4, II , were acertained by results of single crystal X-ray determinations. In the crystals of I—II , the coordination polyhedron of each chromium(0) central atom containing two phosphorous donor atoms in a four-membered chelate ring and four terminal CO ligands is octahedrally distorted. This coordination sphere is connected at the carbon ring atom via a methylen chain group (spacer) with the bidentate amine ligand, which has a secondary and a tertiary nitrogen donor atom. Both nitrogen atoms are coordinated with the Cuac2 under formation of a new kind of [4 + 2]-coordination in a trischelate complex. The six-membered diamine chelat ring in I has a chair-like conformation. The chromium-cadmium complex II is dimer from which the Cd central atoms obtain the rare coordination number of five. The related five-membered diamine chelate ring has δ conformation. 相似文献
997.
Summary The semi-empirical theory on the retention volume in gas chromatography recently developed by some experiments, was found to require partial correction. It was newly refined and summarized. Overall experimental checking was performed by the use of Cl2, Br2, and I2.
Gas-Chromatographie von Halogenen
Zusammenfassung Die halbempirische Theorie über das Retentionsvolumen in der Gas-Chromatographie, die kürzlich an Hand einiger Versuche entwickelt wurde, erforderte eine teilweise Korrektur. Sie wurde verbessert und zusammenfassend dargestellt. Kontrollversuche wurden mit Hilfe von Chlor, Brom und Jod durchgeführt.相似文献
998.
Zusammenfassung Am Beispiel der Bestimmung von Phenacetin und Coffein im pharmazeutisch verwendeten Mengenverhältnis wird die quantitative in situ-Auswertung eines Zweikomponentensystems im on line-Betrieb: Densitometer—Integrator—Tischrechner beschrieben. Die Eichgerade wird für beide Substanzen auf jeder Platte gesondert bestimmt. Durch eine Einschränkung des Konzentrationsbereichs auf obere und untere Toleranzgrenze ergeben sich Vereinfachungen der Ausgleichsrechnungen. Die erzielten Genauigkeiten liegen bei 2 Analysen pro Platte bei 1,51% (Phenacetin) und 2,56% (Coffein) bzw. bei 4 Analysen pro Platte bei 1,50% (Phenacetin) und 2,64% (Coffein) (rel. gen. Standardabweichung, n=18 bzw. n=36).Der Deutschen Forschungsgemeinschaft danken wir für die großzügige Unterstützung dieser Arbeit durch Sach- und Personalmittel. Frau Koch danken wir für die gewissenhafte Mithilfe bei der praktischen Durchführung der Untersuchungen. 相似文献
999.
A new series of group 6 carbonyl complexes of N-[(2-pyridyl)methyliden]-α (or β)-aminonaphthalene (α/β-NaiPy) are described in this work. The complexes are formulated as cis-[M(CO)4(α/β-NaiPy)] by elemental, mass and other spectroscopic data. The complexes show emission spectra at room temperature and their quantum yield lies between 0.4 and 0.5. All the complexes exhibit negative solvatochromism. Cyclic voltammetry shows metal centred oxidation and ligand reductions. 相似文献
1000.
利用自制的烟雾箱系统研究了臭氧与二乙胺和三乙胺的气相反应动力学. 实验过程中保证二乙胺和三乙胺浓度远远大于臭氧浓度, 使得实验在准一级条件下进行. 加入环己烷以消除实验过程中可能产生的OH自由基对反应的影响. 在(298±1) K和1.01×105 Pa条件下, 测得臭氧与二乙胺和三乙胺反应的绝对速率常数值分别为(1.33±0.15)×10-17和(8.20±1.01)×10-17 cm3·molecule-1·s-1. 与文献中已有的其它胺类的臭氧反应数据比较后发现, 臭氧与胺的反应可以用亲电反应机制来解释. 另外, 通过对比发现, 臭氧与三取代的烷基胺类的反应速率要远远大于其与二取代的烷基胺类的反应速率. 这在一定程度上可有助于解释外场观测到的气溶胶相中二烷基胺盐较多的事实. 利用测得的速率常数和大气中臭氧浓度, 还估算了二乙胺和三乙胺与臭氧反应的大气寿命. 结果显示, 与臭氧的反应是二乙胺和三乙胺在大气中的一种重要的消除途径, 尤其是在污染严重地区. 相似文献