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991.
J. Carlsson P. Jönsson L. Sturesson 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1990,16(2):87-90
The lifetimes of the silver 5p 2 P states have been measured with high accuracy by time-resolved laser spectroscopy using the delayed coincidence technique. Also, the hyperfine structure of107Ag and109Ag in these two states has been studied by observing quantum beats. 相似文献
992.
HPLC-separation of cis and trans monounsaturated fatty acids 总被引:1,自引:0,他引:1
Summary The chromatography of monounsaturated fatty acids as their methyl esters on silver nitrate-loaded HPLC-columns has been studied. The separation of cis- and trans-isomers was easily achieved even with columns of low performance. High-performance small-particle-columns treated with silver nitrate separated a large variety of monounsaturated cis and trans positional isomers. The influence of variable silver-loads on the selectivity of the system was studied and a survey of the distribution of positional trans C181 isomers in commercial margarines is given. 相似文献
993.
M. Trömel 《Journal of solid state chemistry》1980,35(1):90-98
The strong variability of bond length between Sb(III) or Te(IV) and oxygen is correlated with distances to more distant oxygen atoms in the trans position. Closer approach of the trans-oxygen atom leads to lengthening of the bond in question. Hyperbolic functions represent suitable approximations for the correlations and give the bond lengths on the average within 0.04 Å. The distance relations are discussed for various limiting coordinations corresponding to 3, 4, and 5. 相似文献
994.
W. Fleischhacker H. Markut F. Vieböck 《Monatshefte für Chemie / Chemical Monthly》1972,103(4):1066-1077
Zusammenfassung Beim Erhitzen von 14-Brom-codeinon-dimethylacetal (1) in absol. Methanol mit einer äquivalenten Menge Na2CO3 entstehen die drei isomeren Methoxycodeinon-acetale3, 4 und5 sowie die beiden Indolino-codeinonderivate6 und7. Die Strukturen und Konfigurationen der Verbindungen3–6 werden auf Grund der NMR- und IR-Spektren sowie durch Umwandlung in bekannte Verbindungen bewiesen.
Herrn Prof.E. Ziegler mit den besten Wünschen zum 60. Geburtstag gewidmet. 相似文献
The methanolysis of 14-bromo-codeinone dimethyl acetal
14-Bromocodeinone dimethyl acetal (1) reacts in methanol containing sodium carbonate (0.5 moles) to give the three isomeric methoxycodeinone acetals3, 4, and5 besides the indolino-codeinones6 and7. The structures and configurations of3–6 were established on the basis of NMR- and IR-spectroscopy and by conversion to known compounds.
Herrn Prof.E. Ziegler mit den besten Wünschen zum 60. Geburtstag gewidmet. 相似文献
995.
The complex generated from 1/2[Ir(OMe)(cod)]2 and 4,4'-di-tert-butyl-2,2'-bipyridine catalyzes the regioselective borylation of ferrocenes, CpMn(CO)3 and CpMo(CO)3CH3 with a stoichiometric amount of B2pin2. 相似文献
996.
The determination of quaternary ammonium ions by capillary electrophoresis (CE) is reviewed. The analytes include tetraalkylammonium and alkylbenzyldimethylammonium compounds frequently used as antiseptic and antibacterial agents as well as in various household products, several plant growth regulators and herbicides, by-products in bile acid sequestrants, and a range of anticholinergic drugs. Besides direct and indirect UV detection, hyphenation with electrospray mass spectrometry is particularly suited for quaternary ammonium ions and may lower the detection limits by two orders of magnitude. In comparison with established liquid chromatographic techniques, CE may exhibits superior separation efficiency. Applications in routine analysis have demonstrated that CE is reliable and robust enough to represent a real alternative to chromatography. 相似文献
997.
Klika KD Imrich J Danihel I Böhm S Kristian P Hamul'aková S Pihlaja K Koch A Kleinpeter E 《Magnetic resonance in chemistry : MRC》2005,43(5):380-388
The configuration and dynamic behavior of O-allyl-S-methyl-N-(acridin-9-yl)iminothiocarbonate (1) and its S-allyl-O-methyl regioisomer (2) were studied using quantum chemical calculations and by applying a novel graphical method to scatter maps obtained from MD simulations for evaluation of an NOE-weighted internuclear distance (r(NOE)). Energy calculations indicated that the Z configuration was predominant for each compound and, further, this was supported both by the calculated chemical shifts and the r(NOE). Both N-inversion- and rotation-type transition-state structures were also calculated for the E/Z isomerization process, the results indicating that the preferred interconversion mechanism for 1 is N-inversion, but contrastingly, interconversion via rotation is equally as probable as N-inversion for 2. This supports the notion that one or the other or both pathways can be active and each system needs to be assessed on a case-by-case basis. 相似文献
998.
Griesbeck AG Heinrich T Oelgemöller M Lex J Molis A 《Journal of the American Chemical Society》2002,124(37):10972-10973
An elaborated protocol is described which allows the efficient transformation of di-, tri-, and tetrapeptides into cyclopeptides with a minimum of protection and activation chemistry using the photoinduced electron transfer initiated decarboxylation of N-phthaloyl peptides resulting in C-C coupling between the initially formed carbon radicals. 相似文献
999.
Nowaczyk S Alayrac C Metzner P Averbuch-Pouchot MT 《The Journal of organic chemistry》2002,67(19):6852-6855
The alkylation of the lithium enolate of enantiopure alpha-cyclohexylsulfinyl thioacetamide 1 with allyl bromides 5 possessing an electron-withdrawing group at the vinylic position does not occur at the sulfur center - as expected in the sulfur series - but at the carbon center through conjugate addition followed by bromide elimination. The modest to excellent 1,2-asymmetric induction achieved by the alkylsulfinyl group (dr up to 100:0) is explained by an electronic model. 相似文献
1000.
Zusammenfassung Es wird die Darstellung von 2-Sulfanilamido-4-methoxy-5-chlorpyrimidin, 2-Sulfanilamido-4-methoxy-5-jodpyrimidin sowie 4-Sulfanilamido-2-methoxy-5-chlorpyrimidin beschrieben. Die erste Verbindung wurde auf zwei voneinander unabhängigen Synthesewegen erhalten.
W. Klötzer undJ. Schantl, Mh. chem.94, 1178 (1963). 相似文献