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41.
Braulio Insuasty Jairo Quiroga Juan Carlos Argoti Samuel Gmez Roberto Martínez Enrique Angeles Rubn Gabio Manuel Nogueras Adolfo Snchez 《Journal of heterocyclic chemistry》1998,35(6):1397-1399
The reaction of 1-aryl-3-(dimethylamino)-1-propanones 1 with one equivalent of 4,5-diamino-1H-pyrimidin-6-ones 2 , in acidic medium, leads to the formation of 4-aryl-2,3,6,7-tetrahydro-1H-pyrimido[4,5-b]-[1,4]diazepin-6-ones 3 . The structure elucidation of the products is based on detail nmr analysis of experiments such as 13C, 1H and DEPT including selective 13C{1H} decoupling experiments. 相似文献
42.
Summary Electrography and paper chromatography were combined to analyse rapidly metallic alloys in an almost non destructive technique. Using anodic dissolution the sample is applied on the start point of the chromatographic paper. Known ketones-HCl-water mixtures are usually used as solvents to analyse electrospots of different alloys and metal coatings and a separate electrospottest is recommended for Cr. Results of qualitative analysis of some steels, Cu–Ni, and Pb alloys are presented. 相似文献
43.
This paper concerns the application of excess adsorption isotherms, measured for solvent mixture/adsorbent systems, to the characterization of TLC data. For this purpose the excess adsorption isotherms for three liquid mixtures: cyclohexane/ benzene, benzene/acetone, and carbon tetrachloride/ethyl acetate on silica gel at 20°C have been measured. These mixtures have been used as binary mobile phases in TLC measurements. It has been shown for a given solute in binary mobile phase that the quantity RM is a simple function of the excess adsorption. Parameters of this function have been used to characterize chromatographic systems with binary mobile phases. 相似文献
44.
Jos R. Ascenso Maria de Deus Carvalho Alberto R. Dias Carlos C. Romo Maria J. Calhorda Luis F. Veiros 《Journal of organometallic chemistry》1994,470(1-2):147-152
The metallocene thioether derivatives [Cp2M(MeSCH2CH2SMe)][PF6]2 (1, M = MO; 2, M = W), [Cp2Mo(SCH2CH2SMe)][PF6] (3) and [Cp2M(SCH2CH2S)] (4, M = Mo; 5, M = W) exhibit temperature-dependent fluxional behavior in solution, owing to the pyramidal sulfur inversion process. The activation energies for this process were determined from proton band-shape analysis in the cases of 1 (54.9 ± 2 kJ mol−1), 2 (51.2 ± 4.6 kJ mol−1) and 3 (30.0 ± 3.1 kJ mol−1). Extended Hückel calculations on related model complexes suggest that local inversion at the sulfur atoms, rather that an inversion of the complete S---C---C---S chain, is responsible for the observed fluxional behaviour. 相似文献
45.
Gómez-Carrasco S González-Snchez L Aguado A Roncero O Alvariño JM Hernández ML Paniagua M 《The Journal of chemical physics》2004,121(10):4605-4618
A theoretical study of the F(2P) + OH(2Pi) --> HF(1Sigma+) + O(3P) reactive collisions is carried out on a new global potential energy surface (PES) of the ground 3A" adiabatic electronic state. The ab initio calculations are based on multireference configuration interaction calculations, using the aug-cc-pVTZ extended basis sets of Dunning et al. A functional representation of the PES shows no nominal barrier to reaction, contrary to previous results by others. Wave packet and quasiclassical trajectory calculations have been performed for this PES to study the F + OH(v = 0,j) reactive collision. The comparison was performed at fixed and constant values of the total angular momentum from 0 to 110 and relative translational energy up to 0.8 eV. The reaction presents a dynamical barrier, essentially due to the zero-point energy for the bending vibration near the saddle point. This determines two different reaction mechanisms. At energies higher than approximately 0.125 eV the reaction is direct, while below that value it is indirect and mediated by heavy-light-heavy resonances. Such resonances, also found in the simulations of the photodetachment spectrum of the triatomic anion, manifest themselves in the quasiclassical simulations, too, where they are associated to periodic orbits. 相似文献
46.
47.
48.
Differential calculus on quantized simple lie groups 总被引:1,自引:0,他引:1
Branislav Jurčo 《Letters in Mathematical Physics》1991,22(3):177-186
Differential calculi, generalizations of Woronowicz's four-dimensional calculus on SU
q
(2), are introduced for quantized classical simple Lie groups in a constructive way. For this purpose, the approach of Faddeev and his collaborators to quantum groups was used. An equivalence of Woronowicz's enveloping algebra generated by the dual space to the left-invariant differential forms and the corresponding quantized universal enveloping algebra, is obtained for our differential calculi. Real forms for q are also discussed. 相似文献
49.
In this work we report the experimental studies of Fe?Mn?Al alloys in the FCC disordered phase at room temperature by Mössbauer spectroscopy and X-ray diffraction. In this phase the alloys are antiferromagnetic with a constant mean hyperfine field ( \(\bar H\) ) near 26 kOe in the composition range from 0 to 7.5 at.% Al and 50 to 65 at.% Fe. When the Al or Fe concentration increases, the \(\bar H\) value gradually decreases to zero and the alloy becomes paramagnetic. In the same way when the Al concentration increases the lattice parameter increases linearly but when the Fe concentration increases the lattice parameter remains nearly constant for alloys with 5 at.% Al and decreases for alloys with 10 at.% Al. 相似文献
50.
Summary Mercury(II) in the presence of a large excess of thiocyanate forms a violet colour with Rhodamine B. The complex formed can be stabilized by addition of poly(vinyl alcohol), and forms the basis for a spectrophotometric method for determination of trace amounts of mercury. The calibration graph for measurement at 610 nm is linear in the range 1–15g of mercury per 25 ml, with a molar absorptivity of 1.1×105l· mole–1·cm·. The effect of foreign ions has been studied and the method can be applied to the determination of mercury in air with reliable analytical results.
Spektrophotometrische Bestimmung von Quecksilber mit Rhodanid und Rhodamin B
Zusammenfassung In Gegenwart eines großen Überschusses von Rhodanid bildet Hg(II) mit Rhodamin B eine violette Färbung. Durch Zusatz von Polyvinylalkohol kann dieser Komplex stabilisiert werden und bietet somit die Grundlage für die spektrophotometrische Bestimmung von Hg-Spuren. Die Eichkurve für die Messung bei 610 nm verläuft für 1–15g Hg/25 ml linear. Die molare Absorptivität beträgt 1,1×105 l·mol–1·cm–1. Die Fremdionenwirkung wurde untersucht. Das Verfahren kann zur Hg-Bestimmung in Luft verwendet werden.相似文献