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51.
Johannes Reisch Arnd A. W. Voerste Michael Top Peter Dziemba 《Monatshefte für Chemie / Chemical Monthly》1992,123(5):473-475
Summary The natural product noracronycine as well as some of its analogs were synthesized by Mitsunobu-etherisation, using propinol derivatives.
Acetylenchemie, 22. Mitt.: Synthese von Noracronycin und einiger Analoga mittels Mitsunobu-Reaktion (Kurze Mitt.)
Zusammenfassung Der Naturstoff Noracronycin sowie einige seiner Analoga konnten durch Mitsunobu-Veretherung unter Verwendung von Propinol-Derivaten synthetisiert werden.相似文献
52.
We prove the conjecture of Gould and Jacobson that a connected S(K1,3)-free graph has a vertex pancyclic square. Since S(K1,3)2 is not vertex pan-cyclic, this result is best possible. 相似文献
53.
The nonlocal contribution of the pi-electrons to the 1H-chemical shifts in the annulenoid systems 1–12 is calculated within the HMO theory from which information is gained about the change of the annulenoid character of (4n) and (4n + 2)-annulenes by different annelated groups. The predicted trends are then compared with experimental data. Calculated ground state stabilization energies and aromaticity indices based on the uniformization of bond lengths show no correlation with the chemical shifts. 相似文献
54.
Eva Rentschler Werner Massa Stefan Vogler Kurt Dehnicke Dieter Fenske Gerhard Baum 《无机化学与普通化学杂志》1991,592(1):59-72
Halogeno-Nitrosyl Complexes of Molybdenum and Tungsten. Crystal Structures of [Na2(15-Crown-5)2(CH3CN)][MoCl4(NO)2] and [Na(15-Crown-5)]2[MoF4Cl(NO)] MoCl2(NO)2 and WCl2(NO)2, respectively, react with excess sodium fluoride in acetonitrile at room temperature and in the presence of 15-crown-5 to give crystalline mixtures, which consist of the title compounds, respectively of [Na(15-crown-5)]2[WCl4(NO)2] and [Na(15-crown-5)]2[WF4Cl(NO)], and which can be separated by selection. The complexes are characterized by their i.r. spectra, the molybdenum compounds additionally by crystal structure determinations. [Na2(15-crown-5)2(CH3CN)][MoCl4(NO)2]: Space group P21, Z = 2, 5415 independent unique reflexions, R = 0.039. Lattice dimensions at ?10°C: a = 984.3, b = 1231.1, c = 1483.0 pm, β = 105.67°. The compound consists of cations [Ne(l5-crown-5)(CH3CN)]+, in which the sodium ion is surrounded by the five O-atoms of the crown ether and by the N-atom of the acetonitrile molecule, as well as of anions, which form an ion pair {Na(15-crown-5)[MoCl4(NO)2]}?. In the in pairs the sodium ion is coordinated by the five oxygen atoms of the crown ether and by two chlorine atoms of the [MoCI4(NO)2]2? unit. The nitrosyl ligands take the cis-position a t the molybdenum atom which is in a distorted octahedrally fashion. [Na(15-crown-5)]2[MoF4Cl(NO)]. Space group C2/c, Z = 4, 1933 independent unique reflexions, R = 0.078. Lattice dimensions at ?7O°C: D : 1.585.8, b = 1171.5, c = 1771.5 pm, β = 114.91°. The compound forms an ion triple, in which the sodium ions are linked to five oxygen atoms each of the crown ether molecules, and to two F-atoms of the [MoF4Cl(NO)]2? unit. The F-atom which is arranged in trans-position to the nitrosyl ligand coordinates with both sodium ions; thus an unusual T-shaped arrangement results for this F-atom. The sole terminal F-Atom and the Cl-atom are disordered in two positions. 相似文献
55.
Sharon M. Molnar Glen E. Jensen Lisa M. Vogler Sumner W. Jones Leroy Laverman Jon S. Bridgewater Mark M. Richter Karen J. Brewer 《Journal of photochemistry and photobiology. A, Chemistry》1994,80(1-3):315-322
We have prepared a series of mixed-metal trimetallic complexes of the form {[(bpy)2Ru(BL)]2MCl2}n+(bpy 2,2′-bipyridine; BL 2,3-bis(2-pyridyl)pyrazine (dpp), 2,3-bis(2-pyridyl)quinoxaline (dpq) or 2,3-bis(2-pyridyl)-benzoquinozaline (dpb); M Ir(III), Rh(III) or Os(II). This new class of trimetallic complexes can be prepared with a good yield, often as high as 95%, using our building block strategy. The central rhodium and iridium fragments of these trimetallic, namely [M(BL)2Cl2]+, have been shown in our laboratory to be capable of delivering multiple electrons, “stored” on the bridging ligand π* orbitals, to a substrate as they functioned as electrocatalysts for the reduction of carbon dioxide to formate. The two terminal ruthenium metals are good light absorbers designed to give rise to photochemical activity. These bichromophoric systems should be capable of absorbing two photons of light, each giving rise to a desired photochemical reaction, namely excited-state electron transfer. Thus these systems form the basis of a molecular device for photoinitiated electron collection. The properties of these supramolecular complexes have been tuned by variation in the central metal and bridging ligand. Comparison of this array of nine complexes is described herein. 相似文献
56.
Ochiai N Sasamoto K Takino M Yamashita S Daishima S Heiden AC Hoffmann A 《Analytical and bioanalytical chemistry》2002,373(1-2):56-63
A method for the simultaneous determination of seven preservatives - sorbic acid, benzoic acid, and p-hydroxybenzoic acid ethyl, isopropyl, propyl, isobutyl, and butyl esters - in beverages, vinegar, aqueous sauces, and quasi-drug drinks has been developed using the stir-bar sorptive extraction technique then thermal desorption GC-MS analysis. The extraction conditions - pH, sample volume, extraction temperature, salt addition, and extraction time - were examined. d5-Benzoic acid and p-hydroxybenzoic acid sec-butyl ester were added as surrogate internal standards to compensate for the effect of sample matrix and coexisting analytes on the sorptive extraction. The linearity of the method was good over the concentration range from 1 to 1000 microg mL(-1) for sorbic acid, 10-1000 microg mL(-1) for benzoic acid, and 0.1-100 microg mL(-1) for p-hydroxybenzoic acid ethyl, isopropyl, propyl, isobutyl, and butyl esters, and the correlation coefficients were higher than 0.9984. The limit of detection ranged from 0.015 to 3.3 microg mL(-1). The recoveries (95-105%) and precision (RSD: 0.86-6.0%) of the method were examined by analyzing a sparkling soft drink, white wine, red wine, balsamic vinegar, soy sauce, and quasi-drug drink samples fortified at the 5 to 50 microg mL(-1) level. 相似文献
57.
58.
Using a photon-particle delayed coincidence method the energy distributions of H +H(2p) and H++H(2p) fragment pairs have been measured arising from collisional dissociation of 10 keV H 2 + ions incident on various target gases. H fragments in their 2p state are identified by the Lymanα radiation emitted. The distribution of H+H(2p) fragment pairs arising from dissociative charge exchange reveals a sharp increase below 0.2 eV in the center-of-mass frame of the H 2 + ion. This is ascribed to predissociation of vibrational levels of higher H2 Rydberg states close above then=2 dissociation limit by those H2 Rydberg states which separate into H+H(2p) fragments. Only direct transitions into the continuum of theGK 1 ∑ g + state may compete. Some structure at 0.3–0.5 eV is attributed to the three statesI 1 П g,i 3 П g, andh 3 bE g + having potential barriers of this height. The distributions for H++H(2p) have maxima at 3.4, 3.8, and 4.2 eV for a H2, Ar, and He target, respectively, indicating that the 2pπ u state as well as the 3dσ g state ofH 2 + is excited. The H+H(2p) process has a greater probability than the H++H(2p) process for Ar and H2 targets, though all electronic H2 states under consideration are bound. 相似文献
59.
Th. Arnd Kühne Sven Odén U. Pratolongo Th. Schloesing E. W. Hilgard G. Richter A. Atterberg J. König J. Hasenbäumer O. Kleine-Möllhof D. J. Hissink M. L. Plonski Ch. J. Moore W. H. Fry H. E. Middleton J. B. Rather O. Lemmermann L. Fresenius L. J. Gillespie L. E. Wise N. M. Comber Ch. Brioux E. A. Fisher Neuman O. Nolte 《Analytical and bioanalytical chemistry》1924,64(5-6):241-248
60.
Th. Arnd Kühne Sven Odén U. Pratolongo Th. Schloesing E. W. Hilgard G. Richter A. Atterberg J. König J. Hasenbäumer O. Kleine-Möllhof D. J. Hissink M. L. Plonski Ch. J. Moore W. H. Fry H. E. Middleton J. B. Rather O. Lemmermann L. Fresenius L. J. Gillespie L. E. Wise N. M. Comber Ch. Brioux E. A. Fisher Neuman und O. Nolte 《Fresenius' Journal of Analytical Chemistry》1924,64(5-6):241-248
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