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103Rh NMR Spectroscopic Evidence of Mixed Nonahalogenodirhodates(III), [Rh2ClnBr9–n]3?, n = 0–9 On heating a mixture of the tetrabutylammonium salts (TBA)3[Rh2Cl9] and (TBA)3[Rh2Br9] at 60°C in propylenecarbonate the complete system of the mixed nonahalogenodirhodates(III) [Rh2ClnBr9–n]3?, n = 0–9 is formed. In the 103Rh nmr spectra 40 different species have been detected, 16 with two equivalent 103Rh atoms each resulting in one singlet and 24 with inequivalent 103Rh atoms each pair giving two resonances. The signals of the geometric isomeres are not resolved. All 64 expected resonances are really observed. By additional measuring of the 103Rh nmr spectra of the fractions n = 0–4 separable by ion exchange chromatography on DEAE cellulose, and utilizing characteristic increments of chemical shifts the complete and unambiguous assignment of all signals is achieved. 相似文献
25.
Dan Peters Anna-Britta Hrnfeldt Salo Gronowitz 《Journal of heterocyclic chemistry》1991,28(6):1629-1631
5-Cyclopropyluracil and cyclopropylcytosine were prepared by the Pd(0)-catalyzed coupling reaction of 5-bromo-2,4-di(trimethylsilyloxy)pyrimidine and 5-bromo-2,4-O,N-bis-trimethylsilylcytosine with tributylstan-nylcyclopropane. The reactions also gave dehalogenated pyrimidine bases as by-products. Attempts to use 2,4-O,N-bis-trimethylsilyl-5-iodocytosine as the halide gave complete dehalogenation. 相似文献
26.
Maurer HH Tenberken O Kratzsch C Weber AA Peters FT 《Journal of chromatography. A》2004,1058(1-2):169-181
A liquid chromatographic-mass spectrometric assay with atmospheric pressure chemical ionization (LC-APCI-MS) is presented for screening for, library-assisted identification (both in scan mode) and quantification (selected-ion mode) of the beta-blockers acebutolol, diacetolol, alprenolol, atenolol, betaxolol, bisoprolol, bupranolol, carazolol, carteolol, carvedilol, celiprolol, esmolol, labetalol, metoprolol, nadolol, nebivolol, oxprenolol, penbutolol, propranolol, sotalol, talinolol and timolol in blood plasma after mixed-mode (HCX) solid-phase extraction (SPE) and separation by reverse-phase liquid chromatography with gradient elution. The validation data were within the required limits. The assay was successfully applied to authentic plasma samples allowing confirmation of diagnosis of overdose situations as well as monitoring of patients' compliance. 相似文献
27.
The reduction behaviour of porous lead dioxide electrodes is shown to be independent of rotation speed in a large excess of 5 M H2SO4. The reduction peak is broadened by the porosity. This porosity broadening is interpreted in terms of the reaction being driven more deeply into the pore structure as the front of the electrode becomes progressively more ressstive. The effect of different potential sweep rates on the current response and the effects of progressive redox cycles can be fully explained on this model. 相似文献
28.
Simple tandemly organized (GTG)n/(CAC)n sequences are spread throughout the human chromosomes. The most informative DNA fingerprints for the testing of pedigrees and/or paternity were obtained with the simple triplet repeat probe (GTG)5 or its complement (CAC)5. These hypervariable simple-repeat fragments are stably inherited in a Mendelian fashion. Using these highly discriminating probes, all human individuals could, theoretically, be differentiated, except for genetically identical monozygotic twins. Examples from actual case work are reported and pertinent advantages of this methodology are discussed. 相似文献
29.
A new direct synthesis of benzo(k,1)thioxanthene-3,4-dicarboxylic anhydride from 4-nitro-naphthalene-1,8-dicarboxylic anhydride and 2-aminobenzenethiol is reported; 4-(2-aminophenylthio) naphthalene-1,8-dicarboxylic anhydride and 4-phenylthionaphthalene-1,8-dicarboxylic anhydride are also formed. Similar reaction in presence of amyl nitrite or sodium nitrite results in formation of larger amounts of 4-phenylthionaphthalene-1,8-dicarboxylic anhydride, together with other products arising from the oxidation of 2-aminobenzenethiol; one such product is the new heterocycle 9,10-dithiaphenanthrene. 4-(2-Aminophenylthio)-naphthalene-1,8-dicarboxylic anhydride is rapidly converted by amyl nitrite or sodium nitrite in dimethylformamide into benzo(k,1)thioxanthene-3,4-dicarboxylic anhydride, constituting a novel one-stage intramolecular cyclisation reaction of greater convenience than the conventional two stage Pschorr cyclisation. 相似文献
30.
Structure of Tetraphenyldisiloxane Tetraphenyldisiloxane 1 crystallizes at 298 K monoclinically (P21/n; a = 1407.6; b = 610.7; c = 1262.7 pm; β = 95.87° Z = 2) and undergoes a second order phase transition at 200 K, in an almost unchanged structure of triclinic symmetry. At 298 K the molecules are already bent (Si? O? Si = 160°) with static or dynamical disorder of the bridging atom. Both Si? O distances are different (156 or 169 pm), because the shift of the bridging O atom is not perpendicular to the Si? to? Si vector. The reason for this remarkable behavior is not yet clear. According to the vibrational spectra, the Si? O? Si bridge is bent in the crystal but, in CCl4 solution a dynamical oscillation through the linear configuration may occur. 相似文献