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551.
552.
Prof. Dr. Oskar Perron 《Mathematische Zeitschrift》1969,112(4):280-288
Ohne Zusammenfassung 相似文献
553.
An algorithm for obtaining the matching polynomial of an arbitrary catacondensed unbranched benzenoid molecule is presented. It is based on multiplication of only three 5 x 5 transfer matrices I, J, K, and an appropriate terminal vector. The choice of the matrices is dictated by the history of the growth of the hexagonal “animals” (i.e., by the pattern of the successive fusions of the benzene rings). The approach also gives the number of Kekule valance structures, the count of conjugated circuits, the values of the topological index Z, and the characteristic polynomials. 相似文献
554.
555.
Ulrich S. Schubert Christian Eschbaumer Oskar Nuyken Georg Hochwimmer 《Journal of inclusion phenomena and macrocyclic chemistry》1999,35(1-2):23-34
[Fe(II){5,5- bis(bromomethyl)-terpyridin}2](PF26)22 complexes were used as metallo-supramolecular initiators for the living polymerization of 2-ethyl-2-oxazolines yielding defined hydrophilic polymers with a central supramolecular building unit and star-like architectures. The living character of the polymerization allows an exact control of the molecular weight as well as the incorporation of additional (complexing) units at the polymer chain ends. 相似文献
556.
Johannes Leitich Oskar E. Polansky Werner Riemer Ursula Ritter-Thomas 《Monatshefte für Chemie / Chemical Monthly》1982,113(4):485-494
Knoevenagel condensation of malononitrile withcis- andtrans-2,5-dimethylcyclohexanone (1
c and1
t, respectively) leads to2
c and2
t, respectively, and withtrans-1-decalone to4
t. The equilibria2
c2
t and4
c4
t have been determined as well as, by means of 270-MHz-1H-NMR, the conformations of these four compounds. The dicyanomethylene group is found to induce axial positions of neighbouring alkyl residues on the cyclohexane ring (or when this is impossible, as in the case of4
t, the twist form of the cyclohexane ring). This results in a strong predominance of thecis isomers in the equilibria2
c2
t and4
c4
t whereas thetrans isomers strongly predominate in the equilibria among the starting ketones. This situation allows the optional preparation of2
c or2
t, and of4
c or4
t, from the more stable starting ketone (or ketone mixture). The free conformational energy of the distorted twist form of4
t amounts to 17 kJ/mol.
Herrn Prof. Dr.E. Ziegler, Graz, zum 70. Geburtstag in aufrichtiger Verbundenheit gewidmet. 相似文献
557.
Oleg V. Surov Nugzar Zh. Mamardashvili Gennadiy P. Shaposhnikov Oskar I. Koifman 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(3-4):329-335
The inclusion of small neutral organic guests (C6H14, CH2Cl2, CH3OH) by calix[4]arene receptors was found by 1H NMR spectroscopy and microanalysis. The studied calix[4]arenes can form stable intramolecular complexes with solvent molecules
which keep the stoichiometric composition without changing under conditions of the sublimation experiment. The saturated vapour
pressures of calix[4]arenes and complexes of calix[4]arenes with solvent molecules were determinated for the first time by
the Knudsen’s effusion method in the wide temperature range. The changing of standard thermodynamic parameters of complexation
by transfer process from condensed state to vapour phase was estimated. It was shown that the large flexibility of the calixarene
ligand structure corresponds to a strongly negative entropic contribution as well as negative enthalpy term to the Gibbs energy
of formation of host–guest complexes in the gas phase. 相似文献
558.
By means of the HMO method a postulate by Clar is justified. According to this postulate certain localized benzene-like regions exist in condensed aromatic hydrocarbons. A measure of the benzene character, butene character, etc., of certain parts of these molecules is derived and a simple method to calculate it is described. The importance of these measurements for discussions of chemical reactivity is pointed out. 相似文献
559.
Martin G. Mayershofer Oskar Nuyken 《Journal of polymer science. Part A, Polymer chemistry》2005,43(23):5723-5747
For many years, considerable research efforts have been dedicated to π‐conjugated polymers because of their extraordinary electronic, optical, and structural properties. The employed transition‐metal‐based initiating systems comprise not only simple transition‐metal salts but also rather sophisticated mixtures of two, three, or four compounds and even highly defined single‐component systems such as transition‐metal alkylidene complexes. Extensive fine‐tuning of the electronic and steric properties of initiator–monomer systems eventually allowed the tailor‐made synthesis of conjugated materials via living polymerization techniques. This article focuses on recent developments in the field of the living polymerization of substituted acetylene derivatives. Ill‐defined group 5 and 6 transition metal halide‐based initiators, well‐defined transition‐metal alkylidene complexes, and rhodium(I)‐based systems that induce the living polymerization of numerous substituted acetylenes are reviewed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5723–5747, 2005 相似文献
560.
Max Ziegler Herbert Sbrzesny und Oskar Glemser 《Fresenius' Journal of Analytical Chemistry》1959,171(4):250-254
Zusammenfassung Die Extraktion des Silbers mit Methylen clilorid als Tri-n-butylammoniumsilberrhodanid erlaubt Trennungen von Blei bis zum Verhältnis AgPb=17500. Das Silber wird aus der nichtwäßrigen Phase mit Schwefelwasserstoff gefällt und gelangt als Ag2S zur Wägung. Es wird gleichzeitig eine Trennung von Wismut bis zum Verhältnis AgBi=l1200 erzielt.Dem Herrn Bundesminister für Atomkernenergie und Wasserwirtschaft und der Deutschen Forschungsgemeinschaft danken wir für Unterstützung. 相似文献