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921.
Zusammenfassung Die Dipolmomente und die Temperaturabhängigkeit derNMR-Spektren sowie des Circulardichroismus der Ferrocenbande von optisch aktiven [3]Ferrocenophanen wurden gemessen. Die Ergebnisse zeigten, daß Substituenten (wie CH3) in -Stellung zur Brücke bevorzugte Konformationen derselben bedingen, wobei im Vergleich zur -Substitution (die praktisch keinen Einfluß ausübt) die Aktivierungsenergie der Inversion stark erhöht wird. Diese bevorzugten Konformationen bestimmen auch die optische Aktivität der Ferrocenbande.
Mit 1 Abbildung
29. Mitt., zgl. 50. Mitt. über Ferrocenderivate:H. Falk, Ch. Krasa undK. Schlögl, Mh. Chem.100, 1552 (1969).
2. Mitt.:H. Falk undO. Hofer, Mh. Chem.100, 1540 (1969). 相似文献
Stereochemistry of metallocenes 30. (Ferrocenes, 51). Optically active [3] and [3][3]ferrocenophanes. 3: Conformational analysis of [3]ferrocenophanes
The dipol moments and the temperature dependence of theNMR spectra as well as of the circular dichroism of the ferrocene band of optically active [3]ferrocenophanes were measured. The results revealed that substituents (such as CH3) in -position with regard to the bridge cause preferred conformations (of the bridge); thereby the energy of activation of the inversion as compared with -substitution (which exerts practically no influence) is strongly increased. These preferred conformations determine also the optical activity of the ferrocene band.
Mit 1 Abbildung
29. Mitt., zgl. 50. Mitt. über Ferrocenderivate:H. Falk, Ch. Krasa undK. Schlögl, Mh. Chem.100, 1552 (1969).
2. Mitt.:H. Falk undO. Hofer, Mh. Chem.100, 1540 (1969). 相似文献
922.
Zusammenfassung Während verschiedene Basen mit organischen Lewissäuren stabile Anbadone liefern, führt die Umsetzung mit Hydrazin zu Aldazinen bzw. Hydrazonen.
13. Mitt.:P. Margaretha undO. E. Polansky, Mh. Chem.100, 576 (1969). 相似文献
Reaction of electrically neutral organic lewis acids with hydrazine (organic lewis acids, XIV)
While several bases reacting with organic Lewis-acids form stable anbadons, the reaction with hydrazine leads to aldazines (azines) and hydrazones.
13. Mitt.:P. Margaretha undO. E. Polansky, Mh. Chem.100, 576 (1969). 相似文献
923.
V. N. Zabaev V. M. Kuznetsov A. P. Potylitsin E. V. Repenko O. I. Stukov B. K. Tomchakov 《Russian Physics Journal》1978,21(5):626-632
This article presents measurements of the asymmetry of formation of + mesons on a proton by linearly polarized photons in the energy region from 220 to 320 MeV and for pion emission angles 90–135° in the c.m.s. Aphenomenological analysis is carried out on the basis of 25 measured values of the asymmetry and the data of other laboratories. As a result of the analysis, five independent values are obtained for the multipole amplitude functions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 94–101, May, 1978. 相似文献
924.
M. R. Corson B. Kolk G. Hoy G. O. Zimmerman A. M. van der Kraan P. C. M. Gubbens 《Hyperfine Interactions》1978,4(1-2):411-414
A3He-4He dilution refrigerator was constructed to perform Mössbauer measurements well below 4.2K. Results are reported here on the pseudobinary Laves-Phase system Y (Fe1-x Cox)2 for x=0.978. We found that at low temperatures, the Fe ions undergo a disordered magnetic phase transition, with a Curie temperature of approximately 4K and a saturation field of 96K0e. The easy axis of magnetization appears to be the [111] direction. This study is an extension to very low temperatures of previous work on the system with 0X0.978.Supported by the NSF Grant No. DMR 73-07665 AO 3 相似文献
925.
Two regions of frequency dispersion of capacitance and conductivity have been discovered in the semiconducting glass ceramics BaTiO3 and KNbO3 which have a positive temperature resistance coefficient (PTRC). The low-frequency region (102–103 Hz) of dispersion is associated with the existence of barrier layers at the electrodes and the high-frequency region (beginning in the region 105–106 Hz), with the existence of barrier layers at grain boundaries. The frequencies fm at which maxima of tan corresponding to both dispersion regions diminish in the temperature range of PTRC whereas in the higher region of PTRC they again increase with a rise in temperature. The anomalous temperature dependence of fm is explained on the basis of the assumption that charge carriers in the barrier layers act as relaxation oscillators and the variations in the barrier heights are described by the Heywang model.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 76–81, September, 1978. 相似文献
926.
The determination of nine rare earth elements in rock samples by epithermal neutron activation, followed by a simple group-separation procedure and Ge(Li) γ-ray spectrometry, is described. This method is found to be advantageous for the determination of Nd, Gd, Ho, Er and Lu by means of the short-lived nuclides149Nd,159Gd,166Ho,171Er and176m Lu. Precision for La, Sm and Eu is similar to that of thermal neutron activation, that for Dy is worse. Samples of the standard rocks, basalt BCR-1 and granite G-2, were analyzed by this procedure and the results obtained are compared with previously reported data. 相似文献
927.
Ya. S. Kayukov P. M. Lukin O. E. Nasakin V. N. Khrustalev V. N. Nesterov M. Yu. Antipin V. V. Sheverdov 《Chemistry of Heterocyclic Compounds》1997,33(4):423-425
It has been established by x-ray structural analysis that on reacting 4-oxoalkane-1,1,2,2-tetracarbonitriles with aldehydes
6-imino-2,7-dioxabicyclo[3.2.1]octane-4,4,5-tricarbonitriles are formed and not 3-imino-2,6-dioxabicyclo[2,2,2] octane-4,8,8-tricarbonitriles
as has been proposed.
Chuvash State University, Cheboksary 428015. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 497–499,
April, 1997. 相似文献
928.
929.
The infrared spectra in the OH-stretching and HOH-bending regions of H2O, and in the OH-stretching region of HDO dissolved in a number of ketones and ethers have been recorded. The number of component bands and their wavenumbers, halfwidths and intensities, as well as the total OH-stretching intensity in each solvent, have been interpreted in terms of a model for the types of hydrogen bonded solvent:water complexes formed in these systems.The effect of temperature on the spectra of H2O in some of the ketones has been rationalized on the basis of the equilibrium existing between the different hydrogen bonded species present in solution. 相似文献
930.
A chelate-forming ion exchanger, iminodiacetic acid/ethylcellulose, is used for the separation of trace metals from waters and different organic solvents. Added uranium was collected from sea waters with recoveries of about 97%. Graphite-furnace atomic absorption spectrometry and solution spectrophotometry were used to quantify the metals. For the direct determination of trace metals in waters by the graphite-furnace method, a simple matrix-matching method is described. The detection limit for cadmium was 0.1 μg l?1 and for lead 1 μg?1 in drinking water. 相似文献