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81.
M. M. Krayushkin L. G. Vorontsova M. G. Kurella M. A. Kalik E. Yu. Zvezdina 《Russian Chemical Bulletin》1994,43(10):1700-1702
The crystal and molecular structure of a novel heterocyclic system, 8-methyl-3,3a,4,5-tetrahydrothieno[3,2:6,7]thiepino[4,5-c]isoxazole, has been determined by X-ray analysis. The seven-membered ring has the boat conformation (B), while the isoxazoline cycle has the flat chair conformation (3E). There are strong steric strains between the vicinal protons at the C(3a), C(3), and C(4) atoms.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1795–1797, October, 1994. 相似文献
82.
ZHOU Hai-cheng XU Sheng PENG Qing LI Ya-dong 《高等学校化学研究》2006,22(1):11-13
IntroductionNano-sized semiconductors are of great interestdue to their special optical and electronic proper-ties[1,2].As one of the mostimportantⅡ—Ⅵsemicon-ductors,CdS has importantapplications in many fields,such as the solar cell field,non linear o… 相似文献
83.
A miniaturised technique to analyse and detect heterocyclic aromatic amines (HAs) using micro solid-phase extraction (SPE) coupled on-line (in-capillary) to capillary electrophoresis (CE) separation with nanospray (nESI) mass spectrometry (MS) detection has been developed. HAs are mutagenic and carcinogenic compounds formed at low levels in protein-rich food during cooking. Due to the low concentrations of HAs and the high complexity of the matrix in which they exist, sensitive and selective analytical methods are required for quantification. SPE was performed on a packed bed of C18 particles inside the CE capillary, which minimised the dead volume. The on-line coupling of SPE, CE and nESI-MS reduced the time for extraction and identification to less than half an hour, which will allow for screening of several samples per day. The new technique provides short analysis time, low sample and solvent consumption, and HAs in standard solutions were easily detected at 12–17 fmol injections, and in spiked urine samples at 750–810 fmol injections. 相似文献
84.
V. Wedelich W. Mehnert K. -H. Frömming 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(5):621-624
-, and -cyclodextrin and heptakis-2,6-di-O-methyl--cyclodextrin enhance the nitrosation rate of l-ephedrine if the nitrosation assay procedure (NAP test) is applied. During this reaction with -cyclodextrin a solid inclusion compound of -cyclodextrin andN-nitrosoephedrine precipitates. Solubilities and stabilities of inclusion compounds of the cyclodextrins with ephedrine and nitrosoephedrine, respectively, explain especially the catalytic effects of some cyclodextrins on ephedrine.Part of the PhD thesis of V. Wedelich, Freie Universität Berlin, 1985. 相似文献
85.
A one-step procedure was developed for the synthesis of new 6-fluoro-7-(isoxazolidin-2-yl)-4-oxo-1,4-dihydroquinolines. The procedure is based on the 1,3-dipolar cycloaddition of the azomethine oxide and 1,1-disubstituted alkenes, which are generated in situ from 6-fluoro-7-hydroxylamino-4-oxo-1,4-dihydroquinoline-3-carboxylic acid and CH-active compounds (dialkyl malonates, ethyl acetoacetate), respectively, in the presence of formaldehyde at 100—120 °C. 相似文献
86.
Summary Two -cyclodextrin (-CD)-containing polymers have been prepared either by condensation of -CD molecules with a bifunctional reagent or by grafting a -CD derivative on to a linear polymer (polyvinylimidazole). HPLC stationary phases were obtained by adsorption of the -CD polymers on to silica. The ability of these chromatographic supports to resolve racemic mixtures of organic compounds such as amino acid derivatives, phenylhydantoins, barbiturates, and hydroxycoumarin derivatives has been investigated. Results were found to depend on the chemical structure of the -CD polymers 相似文献
87.
Ali Taha Viktor Gutmann Wolfgang Linert 《Monatshefte für Chemie / Chemical Monthly》1991,122(5):327-339
Summary The solvatochromic and thermochromic behaviour of a series of mixed Ni(II) complexes with unsubstituted and substituted -diketones and diamines in the solvents 1,2-dichloroethane (DCE), acetonitrile (An), acetone (AC),n-butanol (n-BuOH), formamide (FA), N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO) and pyridine (PY) has been studied and characterized on the basis of electronic spectra. Spectrophotometric methods have been used to evaluate equilibrium constants and their enthalpic and entropic terms for the formation of Ni(-dik)(diam)L
+ and Ni(-dik)(diam)L
2
+
. Increasing donor strength of the donor-solvents (L) and (or) increasing electronwithdrawing parameters of the substituents at the -diketone and the diamine ligands lead to increasing formation constants, paralleled by relative increase in the stability of the five-coordinated species Ni(-dik)(diam)L
+. The results are discussed in terms of the extended donor-acceptor concept.On leave of absence from the Faculty of Education, Ain Schams University, Roxy, Cairo, Egypt 相似文献
88.
89.
V. P. Perelygin S. G. Stetsenko H. J. Crawford T. J. M. Symons 《Zeitschrift für Physik A Hadrons and Nuclei》1991,338(4):435-439
The results are presented of calibrating the sensitivity of olivine crystals from meteorites by the238U nuclei produced at the Bevalac accelerator. The comparative studies of the spectra of the etchable track lengths due to the238U nuclei and to fossil tracks in these olivines have shown that the group of the 210 m fossil tracks observed in 1980 at the LNR, JINR is due to the galactic cosmic-ray nuclei of the Th-U group. As regards the origin of the 340–360 m group of fossil tracks which were considered in [2] to be candidates for superheavy nuclei in cosmic rays the presence of the track with a length of up to 360 m in the calibrating238U track length spectra indicates that the above interpretation has to be questioned. The possible ways of the unambiguous identification of the group of the abnormally long fossil tracks are discussed.In conclusion the authors express their deep gratitude to Academician G.N. Flerov for thoughtful guidance and permanent attention to this study. The authors wish to thank Dr. G.M. Ter-Akopian for very useful discussions and advice and also for his help during the calibrations on Bevalac, Dr. R.I. Petrova for her help in preparing olivine crystal mounts and for their subsequent annealing and etching, and Mrs. G.G. Bankova and G.P. Knyazeva for the thorough microscopic measurements of the238U track spectra. 相似文献
90.
F. Azaiez W. H. Kelly W. Korten M. A. Deleplanque F. S. Stephens R. M. Diamond J. E. Draper A. O. Macchiavelli E. Rubel J. de Boer M. Rohn J. A. Becker E. A. Henry M. J. Brinkman S. W. Yates A. Kuhnert T. F. Wang 《Zeitschrift für Physik A Hadrons and Nuclei》1991,338(4):471-472
Two superdeformed (SD) bands have been found and assigned to195Tl on the basis of excitation function and cross bombardment results. The two bands are almost identical in transition energies to those observed in193Tl. They are signature partners with a splitting, presumably due to the proton i13/2 (=5/2) orbital, characteristic of all known SD bands in the thallium isotopes. Their alignments relative to the193Tl bands were found to be zero.On leave from Comision National de Energia Atomica 1429 Buenos Aires, Argentina. 相似文献