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201.
Xiao Wen Hu Zhi Min Zheng Cai Hong Xu 《中国化学快报》2007,18(11):1351-1352
Three new 1,3-bis(phenylethynyl)disilazanes were synthesized from the reaction of 1,3-dichlorodisilazanes with (phenylethy- nyl)lithium,and characterized by infrared (IR) spectra,nuclear magnetic resonance (NMR) and mass spectrometry (MS). 相似文献
202.
The need for accurate (< 0.06%) isotopic blends of 6Liand 7Li is explained and their preparation is discussed. It is shown that lithium must be determined at an accuracy level better than 0.035%. Four methods — acid-base titration with hydrochloric acid or benzoic acid, and weighing as sulphate or carbonate — were tested and improved for the precise and accurate analysis of lithium hydroxide solutions. The results of these four methods for a 0.1 M solution agreed within ± 0.02%. The preparation of pure isotopically enriched lithium hydroxide solutions, with specially purified cation- and anion-exchangers, is described. The prepared products contain as little as 100 μg of other alkali metals and 50 μg of alkaline-earth metals per gram of lithium, and are sufficiently free of anions to permit accurate chemical assay of lithium. No changes in the isotopic compositions of 99% 6Li or 99.99% 7Li were detected during the treatment. 相似文献
203.
The acid catalized reaction of tri-0-acetyl-D-glucal with benzotriazole or 6-methylthiopurine in acetonitrile gave a mixture of 1',2'- and 2',3'-unsaturated nucleosides, the former predominating. The relationship between these unsaturated nucleosides is studied and an allylic carbonium ion is proposed as an intermediate for these isomerizations. The acid catalized reaction of 1',2'-unsaturated nucleosides with more benzotriazole or 6-methylthiopurine gave 1',3'-two base nucleosides. The conformation and anomeric configuration of the N-glycosyl compounds obtained were assigned by NMR spectroscopy. 相似文献
204.
S. V. Volkov S. V. Kutyakov A. N. Levov E. I. Polyakova Le Tuan An S. A. Soldatova P. B. Terentiev A. T. Soldatenkov 《Chemistry of Heterocyclic Compounds》2007,43(10):1260-1268
It has been established that on heating, 3-benzoyl-4-hydroxy-1-methyl-4-phenylpiperidine is ring-opened in the presence of
arylamines by a type of retroaldol reaction, with subsequent transamination of the intermediate Mannich base and the formation
of 3-arylamino-1-oxo-1-phenylpropanes. When using arylhydrazines this γ-piperidol is recyclized with the formation of 1,3-diarylpyrazoles
and their 4,5-dihydro derivatives. The mass spectral behavior of a series of 3-arylamino-substituted 1-phenylpropanones has
been studied.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1486–1495, October, 2007. 相似文献
205.
Although the theories and potential applications of intermolecular multiple-quantum coherences (iMQCs) have been under active investigations for over a decade, discussion of iMQC NMR signal formation was mainly confined in the time domain. In this paper, a full line-shape theory was developed to describe iMQC signals in the frequency domain. Relevant features of the line shape, such as peak height, linewidth, and phase, were investigated in detail. Predictions based on the theory agree well with experimental and simulated results. Since radiation-damping effects always couple with iMQCs in highly polarized liquid-state NMR systems, and strongly radiation-damped signals have many spectral characteristics similar to those of iMQCs, a detailed comparison was also made between them from different spectral aspects. With detailed comparison of peak height, linewidth, and phase, this work demonstrates that the iMQC and radiation-damping phenomena result from two completely different physical mechanisms despite that both present similar signal features and coexist in highly polarized liquid-state NMR systems. 相似文献
206.
Summary A reversed-phase HPLC method has been developed for the urinary determination of mutagenic 2,4- and 2,6-toluendiamines. These
amines are degradation products of polyurethane, a material used to cover textured silicone breast implants. FMOC-Cl was used
as fluorescent derivatising agent in order to obtain a limit of detection of 15 ng/ml in urine. Pre-treatment of urine samples
was by liquid/liquid extraction and urine specimens of patients after surgury were analysed. 相似文献
207.
Analytically packed columns prepared with Versamid-930, Versamid-900, XE-60, and OV-225 as stationary phases were examined for quantitative gas-liquid chromatography of the potent monamine oxydase inhibitor (MAOI) drugs iproniazid and iproclozide. With the aid of chemically related substances as internal standards, response ratios were determined and linearities calculated by regression analysis. Using the 2-butyl analogs of compounds all four column systems permit quantitation of iproniazid and iproclozide with a percent standard deviation sigmaK of about 1% or less. 相似文献
208.
Electronic structure and spectra of fused n/m ring systems with one or two bridgehead nitrogen atoms
The semiempirical ASMO-SCF-CI method has been applied to study the electronic structures and ultraviolet absorption spectra of the 4-azapentalenyl anion, 4,8-diazapentalene and related azaderivatives. The agreement between observed and calculated transition energies is, in general, satisfactory. Chemical reactivity and assignment of the observed bands are discussed.
Zusammenfassung Mit Hilfe einer semi-empirischen ASMO-SCF-CI Methode wurden Elektronenstruktur und UV Absorptionsspektren des 4-Azapentalenylanions, des 4,8-Diazapentalens und der entsprechenden Azaderivate studiert. Im allgemeinen ist die Übereinstimmung zwischen experimentellen und theoretischen Übergangsenergien zufriedenstellend. Die Zuordnung der beobachteten Banden und Reaktivitäten werden diskutiert.
Résumé La méthode semi-empirique ASMO-SCF-CI a été appliquée à l'étude de la structure électronique et des spectres d'absorption U.V. de l'anion 4-azapentalenil, du 4,8-diazapentalene et de composés aza-derivés apparentés. L'accord entre les énergies de transition observées et calculées est, dans l'ensemble, satisfaisant. La reactivité chimique et l'attribution des bandes observées ont été discutées.相似文献
209.
I. M. Skvortsov I. V. Antipova Yu. A. Pentin Tran Suan Khoan' S. V. Vasil'kovskii 《Chemistry of Heterocyclic Compounds》1975,11(8):949-955
1-(2-Furyl)-3-amino-4,4-dimethylpentane was used to obtain 3-tert-butyl-1,2-dihydropyrrolizine, the catalytic hydrogenation of which over Rh/Al2O3 at room temperature gives a mixture of cis- and trans-3,8-H-3-ter-butylpyrrolizidines with predominance of the cis isomer, whereas hydrogenation at 90–100 °C gives a mixture containing the trans isomer as the principal component. The three-dimensional structures of the isomers follow from data on the catalytic hydrogenation and isomerization and the IR, Raman, and PME spectra. A considerable percentage of the trans-fused form is characteristic for cis-3,8-H-3-tert-butylpyrrolizidine. 相似文献
210.
An alternative convention describing the (n, γ)-reaction rate suited for use in the k0-method of NAA
An alternative convention for use in the k0-method describing the (n, )-reaction rate upon reactor neutron irradiation has been derived by dividing the cross-section in a (v)=0v0/v part and a pure resonance integral, instead of splitting up the neutron spectrum. It describes the (n, )-reactions with the Westcott factor g(T)1 but without resonances below 0.35 eV, and should yield better results for those with resonances below this limit. The resulting formulas are simpler than the ones currently used. An important practical aspect of this new convention is that no irradiations under Cd-cover are needed to determine the parameters to be used in the k0-method. The parameters determined previously for (n, )-reactions with g(T)=1 can still be used. 相似文献