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971.
V. G. Berezkin E. Yu. Sorokina A. I. Sokolov B. A. Rudenko 《Journal of Analytical Chemistry》2003,58(1):61-67
The effects of the presence of water vapor in the carrier gas and the temperature on the retention of achiral and chiral compounds, enantioselectivity, and performance of an open-tubular column with a cyclodextrin-containing phase were studied. The use of a carrier gas containing water vapor in the determination of optically active isomers, such as camphor, slightly increases the retention factor. A substantial improvement of performance characteristics of the column was found: for hydroxy compounds, the column performance increased by two to three times and the peak symmetry improved by more than twice. 相似文献
972.
[structure: see text] The catalytic asymmetric dihydroxylation of olefins has been accomplished with high enantioselectivities using a proline-based catalyst. The pre-transition-state assembly for styrene is shown. 相似文献
973.
Tsventarnyi E. G. Kravtsov V. I. Kurtova O. Yu. 《Russian Journal of Electrochemistry》2003,39(3):215-222
The electroreduction kinetics of Pd(en)2+
2 complexes (0.01 M) is studied on a rotating disk electrode of Pd by recording CVA at 25, 50, and 70°C in solutions of pH 12–13 at ethylenediamine concentrations of 0.03–1.0 M. Established is a diffusion nature of limiting currents, from which diffusion coefficients for Pd(en)2+
2 complexes are calculated. The Pd electrode capacitance, determined by a pulsed galvanostatic method, is used for taking into account the true surface areas of electrolytic Pd deposits. Parameters of the slow electrochemical stage, which involves Pd(en)2+
2 complexes, are determined. The temperature dependence of the rate constant of cathodic reduction of Pd(en)2+
2 complexes is used for calculating an apparent activation energy. An electroreduction mechanism of Pd(en)2+
2 complexes on a Pd electrode is discussed. 相似文献
974.
L. Kh. Bikchurina R. Kh. Yumagulova L. M. Khalilov E. V. Vasil'eva G. V. Leplyanin 《Russian Chemical Bulletin》1990,39(6):1287-1291
The reaction of the acid chlorides of alkylenebisphosphonic acids with ethylene glycol and ethylene chlorohydrin gave ethylene glycol and -chloroethyl esters of alkylenebisphosphonic acids. The quaternization of these products leads to choline esters of alkylenebisphosphonic acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1424–1429, June, 1990. 相似文献
975.
G. A. Golubeva L. A. Sviridova E. S. Besidskii G. S. Besidskaya 《Chemistry of Heterocyclic Compounds》1990,26(4):416-420
Unlike 3-acylindoles, 3-acyl-2-aminoindoles display high selectivity on being electrophilically attacked in the benzene ring, and are substituted at the 6-position. At the same time, an unco-subsitution of the acyl group takes place (to the greatest extent — the formyl group). Direct bromination of 3-acyl- and 3-cyano-2-aminoindoles provides the 6-bromo- and 6,4-dibromo-2-aminoindoles and their derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 486–490, April, 1990. 相似文献
976.
DNA sequences have previously been reported to act as templates for the synthesis of PNA, and vice versa. A continuous evolutionary transition from an informational replicating system based on one polymer to a system based on the other would be facilitated if it were possible to form chimeras, that is molecules that contain monomers of both types. Here we show that ligation to form chimeras proceeds efficiently both on PNA and on DNA templates. The efficiency of ligation is primarily determined by the number of backbone bonds at the ligation site and the relative orientation of template and substrate strands. The most efficient reactions result in the formation of chimeras with ligation junctions resembling the structures of the backbones of PNA and DNA and with antiparallel alignment of both components of the chimera with the template, that is, ligations involving formation of 3'-phosphoramidate and 5'-ester bonds. However, double helices involving PNA are stable both with antiparallel and parallel orientation of the two strands. Ligation on PNA but not on DNA templates is, therefore, sometimes possible on templates with reversed orientation. The relevance of these findings to discussions of possible transitions between genetic systems is discussed. 相似文献
977.
S. V. Ketchik L. M. Plyasova A. E. Seredkin V. V. Kostrov L. N. Morozov 《Reaction Kinetics and Catalysis Letters》1980,14(4):429-434
Structural peculiarities of the formation of copper-aluminium catalysts at copper concentrations <10 wt% and calcination temperatures of 573–1173 K have been studied.
<10% . 573–1173°K.相似文献
978.
The crystal structure of a second high-pressure copper vanadate phase, CuVO3(II), has been determined and refined by full-matrix least-squares procedures using automatic diffractometer data to a residual R = 0.042 (Rw = 0.051). The space group is rhombohedral, , with hexagonal unit cell a = 4.966(2) and c = 14.084(5) Å [aR = 5.501(2) Å and α = 53.66(3)°]. The structure is the fully ordered ilmenite-type and, on the basis of published magnetic data and the interatomic distances, the valence distribution Cu+V5+O3 is proposed. This represents a unique example of Cu+ in an octahedral environment. 相似文献
979.
Zusammenfassung Die komplexe Koazervation im SystemG-A-H2O kann als zweistufiger Prozeß aufgefaßt werden. Das erste Stadium ist die Bildung des elektrisch neutralen Komplexes zwischen G und A unter Einfluß der elektrostatischen Anziehungskräfte. Die Stöchiometrie der gewonnenen Verbindung wird durch die Äquivalenz der Makroionen bestimmt.Nur elektrisch neutrale Komplexe können die neue Phase, d. h. das komplexe Koazervat bilden. Deshalb muß die Zusammensetzung der koazervaten Phase von pH abhängen und bei Veränderung des Verhältnisses der Polymere im Gemisch unveränderlich bleiben.Bei einem Verhältnis der Polymere, kleiner als das stöchiometrische, ist die Bildung geladener Komplexe möglich.Den Prozeß der komplexen Koazervation kann man mittels der Methode der Trübungsmessung bei Cs<6·10–3 g/100 g untersuchen. Hierbei ist die optische Dichte proportional der Menge des komplexen Koazervats oder des elektrisch neutralen Komplexes im System. 相似文献
980.
M. F. Shostakovskii A. S. Atavin E. P. Vyalykh B. A. Trofimov N. A. Vodhol'skaya V. V. Keiko 《Russian Chemical Bulletin》1966,15(7):1239-1240
Conclusions Cyclic alkoxysilanes — 1,3-dioxa-2-silacyclanes — and their oligomers are decomposed by organomagnesium compounds with the formation of the corresponding silanols (disiloxanes) and tetraalkylsilanols.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1283–1285, July, 1966. 相似文献