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101.
Structure of N-Benzoylthiobenzamide N-Benzoylthiobenzamide forms two polymorphic modifications of which the crystal and molecular structures have been determined by X-ray structure analysis. In both modifications the molecules exist as NH tautomeres, but there are differences with regard to their rotameric configurations. In the monoclinic modification both symmetry independent molecules have a Z,Z′ configuration. The triclinic modification also contains two symmetry independent molecules, but now a Z,Z′ and an E,Z′ configuration exist. All four molecules deviate appreciably from planarity. The results of both structure determinations are compared with each other and with the structure of monothiodibenzoylmethane. 相似文献
102.
In this paper we consider problems concerning the effectiveness of iterational calculations on vibrational analysis. Instead of the widespread least-squares method of force field refinement, another method is proposed based on the steepest-descent algorithm for calculation of the functional minimum of many variables. The new method does not require inverting of a large, poorly conditioned matrix or the introduction of experimental damping coefficients for improving the convergency of the calculations. Test calculations performed for several molecules exhibit a significant “elasticity” of the proposed algorithm allowing more precise reproduction of the molecular vibration frequencies than can be found in recently published works. 相似文献
103.
104.
W. Koenig F. -W. Richter J. Ch. Bode B. Meinel 《Journal of Radioanalytical and Nuclear Chemistry》1980,58(1-2):327-339
Multi-element-analysis by PIXE in respect to medical applications is discussed. Examples of trace-element determinations in
liver tissues are given, demonstrating the applicability and usefulness of this rather new analytical technique.
相似文献
105.
The introduction of selected fractions from a liquid chromatograph into a gas chromatograph has been described; however, analyses were performed by off-line experiments requiring collection and reinjection of the separate fractions or by on-line procedures where disadvantageously, only a fraction of the separated peak or a well resolved component in a mixture could be introduced into a gas chromatograph. This disadvantage is overcome by the apparatus and method described in this paper, which utilizes a multidimensional chromatography system employing a high efficiency, packed capillary LC column coupled on-line to a capillary gas chromatograph. The liquid chromatograph (so designed) can act as a highly efficient clean-up or chemical class fractionation step prior to introduction into the gas chromatograph, significantly reducing sample preparation times in many applications. Thus minor components in a complex matrix can be determined without prior sample clean-up, an example of which is the determination of polychlorinated biphenyls in a complex hydrocarbon matrix. 相似文献
106.
Prof. Dr. Stefan Smoliński Janusz Jamrozik Maria Jamrozik 《Monatshefte für Chemie / Chemical Monthly》1977,108(5):1145-1151
We have obtained four new bispirane systems in which both spiroatoms are vicinal atoms in cyclopropane or cyclobutane rings and in which the heterocyclic component has the basic structure of 1,4-dioxep-2-ene. We have shown that from two possibilities (bispiran, propellan) the general reaction leads only to a bispiran system. To the bispiran2 exhibiting the highest hyperchromism we ascribed the bispirocoplanar conformation (Fig. 1).
Mit 3 Abbildungen 相似文献
Mit 3 Abbildungen 相似文献
107.
W. Richter 《Accreditation and quality assurance》1997,2(8):354-359
Primary methods of measurement have a central function in metrology. They are an essential component in the realisation of
the SI units and therefore are indispensable for establishing traceability of measurements of all kinds of physical quantities
to the corresponding SI units. This is also true for chemical analysis. Gravimetry, titrimetry, coulometry, and isotope dilution
mass spectrometry (IDMS) are evaluated with regard to their potential to be primary methods according to a general definition
of primary methods recently given by the Comité Consultatif pour la Quantité de Matière (CCQM). Optical absorption spectrometry
and methods based on colligative properties are also considered. A general scheme for establishing traceability of chemical
measurements to the SI units using primary methods is discussed.
Received: 17 April 1997 · Accepted: 9 August 1997 相似文献
108.
Janusz B. Kyziol 《Journal of heterocyclic chemistry》1985,22(5):1301-1305
The synthesis of 3-nitrosocarbazole (I) by the Fischer-Hepp rearrangement of 9-nitrosocarbazole has been described. The resistance of I to oxidation provides evidence that it cannot be the intermediate in the conversion of 9-nitrosocarbazole to the C-nitro compounds. It has also been shown that I and its derivatives cannot be synthesized by the action nitrosyl chloride on carbazoles. Methylation of I yields 9-methyl-3-nitrosocarbazole, 9,9′-dimethyl-3-azocarbazole and 9,9′-dimethyl-3-azoxycarbazole as the main products. The mechanism of this disproportionation process has been proposed. The spectral data of I are given. 相似文献
109.
Fausi?RassoulEmail author Heinz?L?ster Volker?Richter 《Monatshefte für Chemie / Chemical Monthly》2005,136(8):1501-1507
Summary. L-Carnitine, L-(−)-β-hydroxy-γ-trimethylaminobutyrate, plays an important role as a factor necessary for the transport of long-chain fatty acids into the mitochondria. In order to investigate the influence of L-carnitine on hyperlipidaemias, the experimental model of the sucrose-induced hypertriglyceridaemia of the rat was used. In these experiments L-carnitine in the dose of 11 mg per day and 100 g body weight (over the period of 1 week) was able to antagonize the sucrose-induced hypertriglyceridaemia and the increase of serum free fatty acid level in female rats of the Wistar strain. Carnitine administration did not change the activities of lipogenic enzymes and fatty acid synthesis in the liver. However, L-carnitine increases the rate of hepatic fatty acid oxidation. Our results indicate a hypotriglyceridemic and free fatty acid lowering effect of L-carnitine, and suggest the use of this compound in the therapy of hyperlipidaemias. 相似文献
110.
Various types of sodium cellulose sulfate (SCS), dissolved in a 1M LiCl solution, were investigated by alternating current (AC)polarography. The SCS samples differed in the degree of substitution (DS), thedistribution of substituents within the anhydroglucose unit (AGU), and alongthechain, due to the method of synthesis. The goal was to study theelectrosorptionbehavior, characterized by the shape of the desorption wave in the polarogram,as a function of the chemical structure of the SCS samples. The shape of thedesorption wave reflects domains of different substitution. A superimpositionofparameters like DS and pattern of substitution on the electrosorption behaviorwas observed. The AC polarography method described can be used as a tool todistinguish between an even or uneven distribution of substituents along thecellulose chain. 相似文献