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111.
Gerald Koitz Walter Fabian Hans-Werner Schmidt Hans Junek 《Monatshefte für Chemie / Chemical Monthly》1981,112(8-9):973-985
The synthesis of several 2-aminopyridines is described. The reaction of tetracyanoethylene with 3-imino-propane-carbonitrile gives 2-amino-3,4,5-tricyano-pyridines with alkyl and aryl-substituents, resp., in position 6. Nucleophilic substitution of 2-amino-6-chloro-3,5-dicyanopyridines and 2-amino-6-chloro-3,4,5-tricyano-pyridines with phenolates leads to a variety of pyridines. Spectroscopical data of absorption and fluorescence are presented and the influence of the cyano groups is discussed. The results are in good agreement with quantum chemical calculations (PPP).
Herrn Univ-Prof. Dr.A. Holasek zum 60. Geburtstag gewidmet. 相似文献
112.
"Bare" CeO(2)(+) ions can be prepared in the gas phase by consecutive oxidation of Ce(+) with O(2) and NO(2). The ability to activate saturated and unsaturated hydrocarbons is investigated by use of Fourier-transform ion cyclotron resonance mass spectrometry. In the reactions of CeO(2)(+) with linear and branched alkanes C-H bond activation is observed almost exclusively. In contrast, both oxygen-atom transfer and C-H bond activation processes occur when thermalized CeO(2)(+) cations react with simple alkenes and aromatic compounds. C-C bond activation is not observed at all. Insight into the structural and electronic properties of neutral CeO(2) and cationic CeO(2)(+) is provided by means of quasirelativistic density-functional and ab initio pseudopotential calculations. They reveal a (2)Sigma(u)(+) ground state for CeO(2)(+) which is best described as a linear cerium dioxide with a resonating pi bond. Finally, we discuss the influence of oxo ligands on the chemistry of the cationic CeO(n)()(+) (n = 0-2) species toward hydrocarbons. 相似文献
113.
Gerhard Laus Johannes Schütz Herwig Schottenberger Max Andre Klaus Wurst Mariana Spetea Karl‐Hans Ongania AdrianG. Müller Helmut Schmidhammer 《Helvetica chimica acta》2003,86(10):3274-3280
The two diastereoisomeric ferrocenyl‐substituted orvinols 2 and 3 were prepared. The modified alkaloids are still able to interact with opioid receptors (see Table). The ferrocene moiety allows highly selective and sensitive electrochemical detection. The X‐ray crystal structure of the major isomer 2 was determined. The combination of a metallocene and a morphinan alkaloid holds promise for useful antitumor activity. 相似文献
114.
The reconstruction numberrn(G) of a graphG was introduced by Harary and Plantholt as the smallest number of vertex-deleted subgraphsG
i
=G – v
i
in the deck ofG which do not all appear in the deck of any other graph. For any graph theoretic propertyP, Harary defined theP-reconstruction number of a graph G P as the smallest number of theG
i
in the deck ofG, which do not all appear in the deck of any other graph inP We now study the maximal planar graph reconstruction numberrn(G), proving that its value is either 1 or 2 and characterizing those with value 1. 相似文献
115.
Hans Kummer 《Foundations of Physics》1987,17(1):1-62
An axiomatic theory is formulated which describes a class of yes-no experiments, involving a fixed basic source, a fixed basic detector, and various filters. It is assumed that all filters considered can be constructed from a setP of primitive filters by composition and stochastic selection. Two physically plausible axioms are formulated which allow us to define the concept of asystem in the present context (cf. Definition2.4). To each system we can attach anorder unit module (
) (cf. Definition5.1) whereby (
) is acomplete, separable order unit space. Two additional axioms are proposed which have the effect that the space (
) becomes isomorphic to the order unit space underlying a JB-algebra, at least in the case where
isfinite dimensional (cf. Corollary7.9). 相似文献
116.
Òscar Rubio-Pons Boris Minaev Oleksandr Loboda Hans Ågren 《Theoretical chemistry accounts》2005,113(1):15-27
The phosphorescence spectrum of p-dichlorobenzene has been calculated using multiconfiguration self-consistent-field wave functions and the quadratic response technique. Attention has been paid to the intensity distribution of the singlet–triplet (3B1u1Ag) transition through a number of vibronic subbands. The second order spin–orbit coupling (SOC) contribution to the spin splitting of the 3B1u (3*) state is found to be almost negligible, and the calculations therefore provide a good estimate for the zero-field splitting (ZFS) parameters based only on the electron spin–spin coupling expectation values. Nuclear quadrupole resonance constants for the different Cl isotopes are also calculated to accomplish the ZFS assignment. The electric dipole activity of the spin sublevels in the triplet–singlet transitions to the ground-state vibrational levels is estimated by calculations of derivatives using distorted geometries which are shifted from the equilibrium position along different vibrational modes. A vibrational analysis of the phosphorescence spectrum, based on the SOC-induced mixing of the singlet and triplet states calculated along different vibrational modes, provides reasonable agreement with experimental data.Acknowledgment O. R.-P. would like to thank the European MOLPROP network for support. The authors thank Alexander Baev for fruitful discussions. This work was supported by the Swedish Royal Academy of Science (KVA). 相似文献
117.
Leonard S Van Schepdael A Iványi T Lázár I Rosier J Vanstockem M Vermeersch H Hoogmartens J 《Electrophoresis》2005,26(3):627-632
A capillary electrophoretic (CE) method was developed for the separation of diastereoisomers of a new human immunodeficiency virus (HIV) protease inhibitor TMC114. In total 16 isomers of this drug have been synthesized (eight pairs of enantiomers). We succeeded in the separation of the eight diastereoisomers, but no enantiomers could be separated. Because of the high similarity and water-insolubility of these isomers, the separation is a real challenge. Different CE modes were tried out: capillary zone electrophoresis (CZE), nonaqueous capillary electrophoresis (NACE), micellar electrokinetic capillary chromatography (MEKC), and microemulsion electrokinetic capillary chromatography (MEEKC). Only MEEKC offered resolution of these compounds. 相似文献
118.
We describe a convergent synthesis of eight 1,3,5- and 1,2,4,5-substituted benzene derivatives with long rigid arms containing 4-pyridyl, 2,2'-bipyridyl, and 2,2'-bipyrimidyl termini, meant to be used as trigonal or tetragonal connectors for the construction of large molecular structures. The synthesis involved copper-free Pd-mediated coupling of terminal acetylenes to aryl halides. First, one of the termini of 1,3-diethynylbicyclo[1.1.1]pentane was coupled with a brominated aza heterocycle, and second, 3 equiv of the resulting extended arm were coupled with 1,3,5-triiodobenzene or 4 with 1,2,4,5-tetraiodobenzene. An improved large-scale synthesis for 1,3-diethynylbicyclo[1.1.1]pentane is described. The structures of two of the arms were determined by single-crystal X-ray analysis. Several long molecular rods with 4-pyridyl termini were obtained as byproducts, and a single-crystal X-ray structure is reported for the shortest of these. 相似文献
119.
Thomas R. Gengenbach Zoran R. Vasic Sheng Li Ronald C. Chatelier Hans J. Griesser 《Plasmas and Polymers》1997,2(2):91-114
The properties and composition of plasma polymer surfaces stored in air can change considerably over time, especially as a
result of oxidative reactions. When plasma polymers contain an element other than O, it is possible to probe for mechanisms
in addition to oxidation that contribute to the aging of the surface. Plasma polymers containing N were fabricated from either
1,3-diaminopropane (DAP),n-heptylamine (nHA), or allylamine (AA), and studied by X-ray photo-electron spectroscopy (XPS) and air/water contact angles
(CA). For each of the plasma polymers, a multiexponential increase in the O/C ratio was observed over time using XPS. The
N/C ratios remained constant (AA) or decreased somewhat (nHA and DAP). In contrast, the trends in CA values differed, declining
for the nHA surfaces, rising for the AA, and changing little for the DAP. Surface roughness, assessed by scanning tunnelling
or atomic force microscopy, did not change over time. The diverse adjustments in the polarity of each surface and the similar
compositional changes between them are reconcilable if the aging of the plasma polymer surface is a manifestation of the superposition
of concurrent oxidative reactions and partial surface reorientation; the former introduce polar groups and the latter transports
then from the surface to deeper regions beyond the CA probe depth but within the XPS analysis depth. These processes vary
between different plasma polymers. Data for the alkylamine plasma polymers is also compared with that for two plasma polymers
fabricated from methanol. The change in composition, but not polarity, of the DAP surface after 4 days of storage demonstrates
the importance of using multiple techniques to characterize the aging of plasma polymer surfaces. 相似文献
120.
Josef Janča 《Mikrochimica acta》1994,112(5-6):197-215
The primary field forces can generate spatially oriented gradient of the effective property of a continuum or pseudo-continuum fluid (carrier liquid). When this gradient is coupled with the action of a secondary field of identical or different nature the isoperichoric focused zones of the dispersed species can appear. Consequently, they can be separated according to differences responding to the property gradient of the carrier liquid. This concept can be applied under static (non-flow) conditions in thin layer focusing as well as under dynamic conditions with the elution due to the carrier liquid flow in focusing field-flow fractionation. The gradient established by the action of the primary field and the concentration distribution of the isoperichoric focused zone formed by the coupled effect of the gradient and of the primary or secondary field are described theoretically. The rigorous relationship describing the shape of the focused zone is compared with the approximate solutions. The performances of the proposed principle were evaluated by model calculations. Potential experimental configurations considering the implementation of the static and dynamic conditions are discussed. The generalized isoperichoric focusing theory can be applied to describe the particular processes operating in analytical and preparative focusing separations of the particles of various, but especially of biological origin. 相似文献