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991.
New polymethine dyes with an indolo[3,2-d]thiazole residue are described, and their spectral properties are discussed. Replacement of the vinylene group in the naphtho[1,2-d]thiazole residue by an NH group leads to a considerably greater bathochromic shift of the absorption maximum of carbo- and merocyanines as compared with replacement by a sulfur atom. The basicity of the indolo[3,2-d]thiazole residue is higher than the basicity of the naphtho[1,2-d]-thiazole and thionaphtheno[3,2-d]thiazole residues.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1606–1610, December, 1972. 相似文献
992.
A method is proposed for selective complexometric determination of palladium, thiourea being used as masking agent. An excess of EDTA is added and the surplus EDTA is back-titrated at pH 5-5.5 with lead nitrate, with Xylenol Orange as indicator. Thiourea is then added to decompose the palladium-EDTA complex and the liberated EDTA is again back-titrated with lead nitrate. The interference of various cations has been studied. 相似文献
993.
CD spectra of acyclic α-N,N-dimethylamino ketones exhibit two absorption bands of opposite sign at ca. 240 and 305–315 nm. Both bands are ascribed to the same conformers. On protonation only one CD band is seen. The single CD band of α-N,N,N-trimethylammonio ketones has the same sign and almost the same wavelength maximum as the protonated amino ketones. 相似文献
994.
O. V. Statsenko S. N. Bolotin V. T. Panyushkin 《Russian Journal of General Chemistry》2004,74(8):1286-1288
Complexation of Cu(II) ions with L- and DL-threonine in aqueous solution was studied. Treatment of the ESR spectra of solutions containing Cu(II) and threonine in various ratios and having various pH, involving total line shape analysis, revealed formation of geometric isomers of the complex ions [Cu(thrH–1)2]2– differing in the mutual arrangement of the N and O atoms in the equatorial plane; the complexation and isomerization equilibrium constants were determined.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 8, 2004, pp. 1388–1391.Original Russian Text Copyright © 2004 by Statsenko, Bolotin, Panyushkin.This revised version was published online in April 2005 with a corrected cover date. 相似文献
995.
A few 2-substituted 1-(1-ethoxyethyl)benzimidazoles have been prepared and the rate constants for their hydrolysis measured at various temperatures and oxonium ion concentrations. The formal kinetics followed and the effect of varying the 2-substitution on the hydrolysis rate suggest that the acid-catalyzed cleavage of these compounds involves a rapid initial protonation of the benzimidazole ring and a subsequent rate-limiting heterolysis of the protonated substrate to form a free nitrogen base and an ocarbenium ion derived from the ethoxyethyl group. The values obtained for the entropy of activation are consistent with the assumed unimolecular nature of the rate-limiting step. The effects of 2-substituents on the acidities of the protonated substrates and their heterolysis rates have been compared. The latter partial reaction has been suggested to be the subject of steric acceleration. 相似文献
996.
A.B. Zolotoy O.A. Dyachenko L.O. Atovmyan I.P. Yakovlev V.O. Reichsfeld 《Journal of organometallic chemistry》1980,190(3):267-276
The structure of 5-ethyl-5,10-dihydro-10,10-diphenylphenazasiline has been determined from three-dimensional X-ray data collected by counter methods. The compound in the monoclinic space group P21/b with a 10.782(5), b 22.642(9), c 8.830(4) Å and γ 74°41′(2). The observed and calculated densities (Z = 4) are 1.22 and 1.21 g cm-3, respectively. Anisotropic(Si, N, C)-isotropic block-diagonal least squares refinement gave a conventional R factor of 3.9% for 1871 reflections with I>2σ(I). The central six-membered ring of the tricyclic system adopts a boat conformation; the dihedral angle between the benzo-group planes is 157.3°. The CSiC angle in the heterocycle is 101.1(1)°; the mean SiC bond length is 1.850(2) Å (in the cycle) and 1.862(2) Å (with Ph group). The nitrogen atom is displaced 0.05 Å from the plane of the adjacent carbon atoms; the sum of the angle about N is 359.7°. 相似文献
997.
K G Wahlung 《Journal of chromatography. A》1975,115(2):411-422
A reversed-phase partition chromatographic system for separation of organic anions as ion pairs with quaternary ammonium ions has been developed. Commercial, hydrophobized silica supports are used with 1-pentanol as stationary phase and aqueous solutions of tetrabutylammonium (TBA) as mobile phase. The separation of the aromatic sulphonates and benzoic acid derivatives is demonstrated. The use of the TBA concentration of the mobile phase to regulate the capacity factor of the anions, as a means of improving separation by gradient elution and direct injection of large sample volumes, is demonstrated. The isolation of nicotinic acid from human serum samples is shown. 相似文献
998.
A comparison of some results from Xα-scattered wave (Xα-SW) and extended Hückel (EH) calculations for metal clusters is given. It is found that small clusters of atoms (≈ 13 atoms) using the Xα-SW method reproduce many of the features of the electronic structure of the bulk metals, whereas this is not the case for the same clusters using the EH method. A more systematic approach to EH parametrizations is suggested in order to make this method a more viable approach to treating metal clusters. 相似文献
999.
Organoantimony Compounds. V. The Reactivity of Phenyl Stibine C6H5SbH2, synthesized by the reduction of C6H5SbCl2 with LiBH4, reacts with LiR under certain conditions forming (C6H5Sb)n and H2 or give by a partially elimination of H2 stibides with a different structure. The latter react with alkyl and aryl halides forming tert. stibines which may be characterized as the corresponding dibromides. The preparation of C6H5SbNa2 and its reaction with C2H5Br, Cl(CH2)4Cl and C6H5(Cl)C?N? N?C(Cl)C6H5 are described. 相似文献
1000.
Dipl.-Ing. Dr. O. Hinterhofer 《Monatshefte für Chemie / Chemical Monthly》1974,105(2):279-290
The selective chlorination of a m/p-xylene mixture, followed by distillation of the unreacted p-xylene, leaves a residue containing up to 90% of monochlorinated m-xylenes. m-Xylene is recovered from the latter by heterogeneous catalytic hydrogenolysis in the gas-phase. It was found that the hydrogenolysis on certain noble metal catalysts proceeds according to an ionic reaction mechanism at temperatures below a definite temperature range. At temperatures above this range hydrogenolysis follows a radical reaction mechanism. 相似文献