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991.
V. V. Lapachev O. A. Zagulyaeva S. F. Bychkov V. P. Mamaev 《Chemistry of Heterocyclic Compounds》1978,14(11):1257-1260
The tautomeric properties of 4-pyrimidinylmethanes were studied in the case of 2-CH3- and 2-CF3-4-pyrimidinylcyanoacetic esters, 2-CH3-4-pyrimidinylnitromethane, and 4-pyrimidinylnitromethane. It was shown by 1H and 13C NMR spectroscopy that an equilibrium with the participation of three tautomeric forms — pyrimidine form A and pyrimidinylidene forms B and C with o- and p-quinoid orientations of the double bonds in the heteroring — may be realized in aprotic dipolar solvents (dimethyl sulfoxide).See [1, 2] for communications I and II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1544–1548, November, 1978. 相似文献
992.
A simplified micro-method for the quantitative analysis of urinary polyamines is described. After acid hydrolysis of urine, the polyamines are converted to fluorescent 1-dimethylaminonaphthalene-5-sulfonyl (Dns; dansyl) derivatives and separated by means of thin-layer chromatography. Dns-NH2, which has been reported to interfere with the determination of putrescine, is well separated from di-Dns-putrescine. Putrescine, spermidine and spermine are quantitated by in situ scanning of their fluorescent spots on the chromatogram. The present method is both sensitive and reproducible. It eliminates a number of time-consuming steps and thus reduces preparative losses. Yet an adequate chromatographic resolution is obtained. Representative polyamine analyses of urine from normal volunteers and from cancer patients are reported. Elevated levels occur in the urines of pregnant women and of patients with various types of cancer. 相似文献
993.
New ionization potential values are reported for sixteen aromatic molecules. They are obtained from CT spectra of a new electron acceptor, 3,5-dinitro-phthalic anhydride with the aromatic electron donors in 1,2-dichloroethane. The results are correlated with molecular electronic structure using perturbation theory. 相似文献
994.
Prof. Dr. O. Hromatka D. Binder K. Eichinger 《Monatshefte für Chemie / Chemical Monthly》1974,105(1):123-126
The synthesis of 5-(o-trifluoromethylphenyl)-1H-thieno-[3,4-e]1,4-diazepin-2(3H)-one (7) and its nitration and chlorination in pos. 8 are described. 相似文献
995.
O. B. Bondarenko A. Yu. Gavrilova M. A. Kazantseva V. N. Tikhanushkina E. E. Nifant’ev L. G. Saginova N. V. Zyk 《Russian Journal of Organic Chemistry》2006,42(2):249-255
A reaction of monoarylcyclopropanes with nitrosyl chloride activated by sulfur (IV) oxide gave in good yields 5-arylisoxazolines. The reaction is of electrophilic character. A scheme of the reaction was suggested. 相似文献
996.
F. J. Krug L. C. R. Pessenda E. A. G. Zagatto A. O. Jacintho B. F. Reis 《Analytica chimica acta》1981,130(2):409-413
A flow injection procedure is described for the spectrophotometric determination of chloride in ethanol, based on the mercury(II) thiocyanate—iron(III) reaction. Effects of reagent composition and ethanol content of the sample are investigated in detail. The proposed system can analyse 120 samples of ethanol (94–100% v/v) per hour, with a relative standard deviation lower than 1%, when the chloride content ranges from 0.1–6.0 ppm. Recoveries of ca. 96% are found. 相似文献
997.
A. I. Druzhinina O. V. Krol’ A. A. Efimova R. M. Varushchenko L. L. Gervits 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(11):1742-1748
The borling temperatures of perfluoro-2,4,6,9,11,13-hexaoxy-n-tetradecane, perfluoro-2,4,6,8,11,13,15,17-octaoxy-n-octadecane, and perfluoro-2,4,6,8,11,13,15,17,19,21-decaoxy-n-docosane were determined by comparative ebulliometry over the saturated vapor pressure range 6.2–101.6 kPa. The heat capacity of perfluoro-2,4,6,8,11,13,15,17-octaoxy-n-octadecane was studied by adiabatic calorimetry over the temperature range 5.3–371.2 K. The densities of the substances at 296–338 K were measured in quartz pycnometers. The data obtained were used to calculate the normal boiling points, enthalpies of vaporization, critical parameters, and thermodynamic functions (entropy, enthalpy, and Gibbs energy) of the polyethers studied. 相似文献
998.
O. R. Sergeeva V. V. Chenets V. G. Lipovich 《Reaction Kinetics and Catalysis Letters》1982,19(3-4):411-414
Kinetic isotope effect (KIE) measurements in the trans-alkylation of toluene and benzene with ethylbenzene in hexane in the presence of AlBr3 at 313 K indicate that deuterium in the toluene methyl group causes a small inverse KIE characteristic for a -complex transiton state. The small direct KIE found for the reaction with C2D5C6H5 does not agree with a mechanism involving alkyl-and -phenylalkyl cations.
() - AlBr3 313 . , , - C2D5C6H5 , - -.相似文献
999.
O. Yu. Nadzhafova M. V. Drozdova E. V. Nebesnaya V. B. Ishchenko 《Journal of Analytical Chemistry》2007,62(12):1136-1142
Conditions are optimized for preparing sol-gel modified composite films based on silicon oxide and polyvinylsulfonic acid in the presence of the Tween 20 nonionic surfactant as a template for the adsorption of Fe(II) and Zn(II) phenanthrolinates. The adsorption of Zn(II), Cu(II), Mn(II), Co(II), and Ni(II) phenanthrolinates followed by their development on the surface with Rose Bengal oxyxanthene dye was studied by spectrophotometry. The variation of the pH of the solution pH and the addition of 0.01 M of EDTA enhanced the selectivity of determining Zn(II) using a film obtained under optimum conditions. The applicability of the proposed thin-film coatings to the adsorption-spectrophotometric determination of Fe(II) and Zn(II) in the ranges of 0.2–5.6 and 0.3–5.0 mg/L, respectively, was shown. The procedure was used to determine zinc in vitamin preparations, a food supplement, and an insulin preparation. The accuracy of determination was checked by atomic absorption spectrometry. The detection limit for zinc was 0.06 mg/L at a liquid phase volume of 25 mL and absorption layer thickness of 0.015 ± 0.003 mm. 相似文献
1000.