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971.
D. A. Rakhimov M. Kh. Malikova A. A. Vakhabov T. R. Abdurakhmanov O. I. Ruziev 《Chemistry of Natural Compounds》1997,33(5):534-535
A polysaccharide possessing pronounced direct-action anticoagulant activity has been isolated from the epigeal part ofLagochilus usunachmaticus.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 40 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 690–692, September–October, 1997. 相似文献
972.
Douglas O. Spry Anita R. Bhala Wayne A. Spitzer Noel D. Jones John K. Swartzendruber 《Tetrahedron letters》1984,25(24):2531-2534
The major product from the thermolysis and photolysis of C(3)-azido cephem 2 is the ring expanded 1,4,6-thiadiazepine azetidinone. 相似文献
973.
Three recently introduced benzodiazepine derivatives, tetrazepam (I), nortetrazepam (II) and menitrazepam (III) have been subjected to spectral and polarographic investigation. From the ultraviolet spectral data their pK(a)-values have been determined: 4.28 (I), 4.3 (II) and 3.5 (III). From the polarographic measurements it can be concluded that in I and II the 4,5 CN double bond is reduced with 2 electrons. For the first time for the benzodiazepine series it has been observed that in slightly alkaline solutions this process takes place in two separate 1-electron steps. In III, first the aromatic nitro group is reduced to a hydroxylamine group, then at more negative potentials the CN double bond is also reduced; its reduction wave mostly coalesces with that for the 6-electron reduction of the nitro group to an amino group. A differential pulse polarographic method is presented, for the determination of I, II, III at concentrations as low as 10(-7)M. 相似文献
974.
Complexation processes that occur when hexacyanoferrate(II) immobilized in gelatin is brought into contact with aqueous solutions of dithiooxamide at pH 12 are studied. Unlike the binary metal ion–dithiooxamide systems studied so far, the final product in this case was Pb(II) sulfide, rather than the Pb(II) complex with the indicated ligand. Concentration of Pb(II) sulfide was shown to depend on dithiooxamide concentration in a solution in contact with the matrix. A scheme for the complexation process is proposed. 相似文献
975.
Zusammenfassung Die durch Umsetzung von 5-Methyltryptamin, 5-Äthoxytryptamin und 5-Methylmercapto-tryptamin (I, R=CH3, OC2H5 bzw. SCH3) mit dem racemischen Aldehyd-Ester II entstandenenSchiffschen Basen wurden durch Natriumborhydrid-Reduktion in Methanol unter gleichzeitiger Cyclisierung und Desacetylierung in die entsprechenden 10-substituiertendl-Methyl-2,3-seco-3-oxodeserpidate (IV) übergeführt. Die bei der Einwirkung von 3,4,5-Trimethoxybenzoylchlorid in Pyridin erhaltenen Ester V wurden weiter mit Phosphoroxychlorid cyclisiert und die Produkte als Perchlorate (VI) mit Zink in sauerer Lösung zu den entsprechenden 10-substituiertendl-Deserpidinen (VII, R=CH3, OC2H5 bzw. SCH3) reduziert. Mit Hilfe der Chromatographie gelang es in zwei Fällen, aus den Rohprodukten auch die entsprechendendl-3-Isodeserpidine (VIII, R=CH3 bzw. OC2H5) zu isolieren. Zum Unterscheiden der Produkte der normalen Reihe (VII) und der 3-Iso-Reihe (VIII) wurden IR-Spektren und die Papierchromatographie angewendet.Mit 2 Abbildungen 相似文献
976.
M. A. Zuenko M. P. Nemtseva O. V. Lefedova E. V. Gladkova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(2):164-168
The scheme of chemical transformations of 2-nitroazobenzene derivatives during catalytic hydrogenation on Raney nickel was found to be common to compounds containing electron donor and electron acceptor substituents. A qualitative correlation between solvation interaction parameters and the solubility of substituted 2-nitroazobenzenes was observed. The selectivity of the reaction with respect to intermediate products was determined by the composition of the solvent and weakly depended on the nature of the substituent. The introduction of sodium hydroxide and acetic acid into solvents ensured high selectivity of the hydrogenation of substituted 2-nitroazobenzene derivatives with respect to the corresponding N-oxides and nitrohydrazo derivatives, respectively. 相似文献
977.
R. González-Ramírez H. Jiménez-Domínguez O. Solorza-Feria E. Ordóñez-Regil A. Cabral-Prieto S. Bulbulian 《Journal of Radioanalytical and Nuclear Chemistry》1993,174(2):291-298
Conditions for the electrodeposition of59Co and57Co on stainless steel foils have been studied. A set of electrolytic parameters has been determined to get a reasonably good electrodeposited sample. The57Co electrodeposited foil was then introduced in a quartz tube to be annealed in an argon flow. The final product was a 11 Ci Mössbauer source for college experiments which was succesfully tested by obtaining spectra of stainless steel and sodium nitroprusside. 相似文献
978.
T. V. Rybalova V. F. Sedova Yu. V. Gatilov O. P. Shkurko 《Chemistry of Heterocyclic Compounds》1998,34(10):1161-1165
The crystal structure of 2-nitropyridine has been determined by x-ray diffraction analysis. The influence of the nitro group
on the geometric parameters of the molecule was evaluated, as well as its influence on the molecular parameters of other nitropyridines,
depending on the position of this group in the pyridine ring.
Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090. E-mail:
gatilov@nioch.nsc.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1367–1371, October, 1998. 相似文献
979.
The simple determination of the sum of weak (polycarboxylic) acids in aqueous solutions and titratable acidity of wines based on indirect iodate-iodide potentiometry without titration was described. 相似文献
980.
Bobby L. Wilson Rudolph R. Schwarzer Callista O. Chukwuenye 《Microchemical Journal》1982,27(4):558-563
This paper reports the development of a field electrode method for the determination of total sulfide in water. The method involves the use of preweighed sodium sulfide crystals in the standardization process. Sodium sulfide crystals were weighed and sealed in air-tight plastic volumetric flasks. Standards were prepared in the field by adding a sulfide antioxidant buffer to the flasks containing the sulfide crystals and diluting it to mark with deionized deaerated water. Standards of lower concentration were prepared by serial dilutions of first standards.The results of the reproducibility determination revealed that sulfide concentrations as low as 6 ppb could be measured with a reproducibility of better than ±10%.Water samples were collected from a series of lakes in Fort Bend County, Texas (near Houston) and analyzed for sulfide content. The sulfide ion concentrations of these samples were determined directly in the field by use of an Orion Model 407A/F specific meter equipped with a silver/sulfide ion selective electrode in conjunction with a double junction reference electrode. 相似文献