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  • Wiley-Blackwell  (3,970)
  • American Meteorological Society
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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 649-656 
    ISSN: 0947-3440
    Keywords: Catenanes ; Interlocked rings ; Mechanical bond ; Photoswitches ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four catenanes (1-4) and the corresponding tetracationic monocycles 5-8 are synthesized. X-ray structural analyses allow a prediction of the mobility (circumrotation) of the „interlocked“ rings in the catenanes, which is proven by 1H-NMR spectroscopy. An unexpected order in the crystal packing of 6 is demonstrated. (E/Z) isomerization in one ring influences the second ring of 1-4 and inversely. An existing obstacle inside the cavity of the switchable macrocycle can block this isomerization completely.
    Additional Material: 2 Ill.
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  • 2
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: This paper is concerned with the ring opening of the uretdione group in presence of nucleophilic partners and of the technological significance of this reaction. It is shown that at temperatures from 100° to 120°C both polyesters containing hydroxyl groups and low-molecular weight compounds carrying Zerewitinow-active hydrogen atoms react in solution as well as in the molten state with free NCO groups of uretdione diisocyanates by the diisocyanate polyaddition process. Under these conditions no opening of the uretdione ring occurs.These results give rise to the use of uretdione diisocyanates for chain extensions yielding polyuretdione polyurethanes. Reactions with blocking agents (e.g. ε-caprolactam) result in new types of blocked uretdione and blocked polyuretdione polyurethanes. It is shown that the four-membered rings are split completely at temperatures from 140° to 180°C. Compounds containing hydroxyl groups which are available in the reaction mixture react with the latent NCO groups of the uretdiones to form urethanes. By selection and combination of suitable starting compounds crystalline, high-melting polyuretdione polyurethane powders of good milling properties can be obtained. The new syntheses of technical usefulness yield non-polluting polyurethane powder coatings for application by electrostatic spraying.
    Notes: Die Ringöffnung der Uretdiongruppe in Gegenwart von nukleophilen Reaktionspartner und die technische Bedeutung dieser Reaktionsind Gegenstand der vorliegenden Arbeit. Die Untersuchungen machen deutlich, daß hydroxylgruppenhaltige Polyester und niedermolekulare Zerewitinow-aktive Wasserstofftome tragende Verbindungen sich bei Temperaturen von 100-120°C in Lösung, aber auch in der Schmelze mit den freien NCO-Gruppen der Uretdiondiisocyanate nach dem Diisocyanat-Polyadditionsver-faren umsetzen lassen, ohne daß nennenswerte Uretdionringöffnung eintritt. Auf Grund dieser Erkenntnis können mit den Uretdiondiisocyanaten Kettenverlängerungen zu Poly-uretdionpolyurethanen durchgeführt werden. Durch Umsetzung mit Blockierungsmitteln (z.B.ε-Caprolactam) werden neuartige blockierte Uretdione und blockierte Polyuretdion-polyurethane erhalten. Es wird nachgewiesen, daß die Vierringe im Temperaturbereich von 140-180°C vollständig aufspalten. Gleichzeitig vorliegende hydroxylgruppenhaltige Verbindungen reagieren mit den latenten NCO-Gruppen der Uretdione unter Urethanbildung. Durch geeignete Wahl und Kombinatio der Asgangsverbindungen lassen sich kristalline, hochschmelzende, gut mahlbare Polyuretdionpolyurethanpulver gewinnen. Die neuen technisch verwertbaren Synthesen führen zu umweltfreundlichen, lösungsmittel-freien Verfahen der elektrostatischen Pulverbeschichtung.
    Additional Material: 1 Ill.
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  • 3
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Metallocen-Katalysatoren eröffnen neue Wege zur Synthese von Olefinoligomeren und -polymeren, deren Molekulargewichte und Schmelzpunkte in weiten Bereichen variieren. Einige wichtige Besonderheiten bei der Herstellung von Oligomeren, von wachsartigen sowie von hochmolekularen Polymeren durch Metallocen-Katalyse werden hier behandelt. Am Beispiel der Oligomerisation von Hexen wird ein einfaches kinetisches Modell entwickelt, das geeignet erscheint, den Reaktionsverlauf und die resultierende Oligomerenverteilung beim Einsatz von Metallocen-Katalysatoren zu beschreiben. Die Herstellung von Propylenpolymeren mit niedrigen und hohen Molekulargewichten durch Metallocen-Katalyse wird hinsichtlich der Reaktionsbedingungen und der Produkteigenschaften mit bekannten Prozessen verglichen. Ferner wurde der Einfluß von verschiedenen Unregelmäßigkeiten der Polymerketten, wie Kettenenden, Regioirregularitäten und Comonomersegmenten auf die Schmelzpunkte untersucht.
    Notes: Metallocenes offer new synthetic routes to olefin oligomers and polymers covering a wide range of molecular weights and melting points. This paper deals with some important features of the preparation of oligomers, wax-like polymers as well as highmolecular-weight polymers via metallocene catalysis. Taking the oligomerization of hexene as an example, a simple kinetic scheme is established, which is suitable to describe the course of the reaction and the resulting oligomer distribution with metallocenes as catalysts. For low and high-molecular-weight polymers, the metallocene route to polypropylene is compared to existent processes in terms of reaction conditions and product properties. An attempt is made to separate the effect of different chain defects like chain ends, regioirregularities and comonomers on the melting point.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 99 (1966), S. 2479-2490 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Lokalisationsenergien Lr+ einer Anzahl konjugierter Polyene weisen auf ihre leichte Substituierbarkeit durch Vilsmeier-Komplexe hin. Bei Kohlenwasserstoffen mit dem System des 2-Vinyl-butadiens-(1.3) und 2-Phenyl-butadiens-(1.3) gelingt Monoformylierung zu Imoniumsalzen. Isobutylen wird fünffach zu einem gelben Trikation substituiert, beim 2-Phenyl-propen konnten die Salze der Mono- und Triformylierung isoliert werden.
    Additional Material: 3 Ill.
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  • 5
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Targeting to specific sites of the body via colloidal carriers is sought in order to reduce drug side effects. The adsorption of plasma proteins on intravenously injected particles is regarded as the key factor in explaining their organ distribution: total bound protein, or, more likely, the presence of specific proteins and their conformation, are expected to influence macrophage uptake. Polystyrene beads, 60 nm in diameter, were used as model carriers; their surface was differentially modified by adsorption of increasingly hydrophilic block copolymers, poloxamers 184, 188 and 407. After incubation in plasma, the patterns of protein adsorption onto coated beads were analyzed by high-resolution two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). The behavior of some representative proteins was monitored, including albumin, fibrinogen, IgG, factor B and the apolipoproteins, A-I, A-IV, C-III, E and J. The more hydrophobic the particles, the larger the total amount of bound protein. However, this correlation was not valid for all of the analyzed protein species, which proves that it is insufficient to look only at physico-chemical data to predict organ distribution. On the contrary, it is essential to use 2-D PAGE to establish the correlation between adsorbed proteins and carrier behavior in vivo.
    Additional Material: 5 Ill.
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  • 6
    ISSN: 0173-0835
    Keywords: Two-dimensional polyacrylamide gel electrophoresis ; Protein sequencing ; Amino acid analysis ; Matrix assisted laser desorption ionization-mass spectrometry ; Database ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The master gel of the human myocardial two-dimensional electrophoresis (2-DE) gel database contains about 3300 protein spots characterized in terms of isoelectric point (pI) and molecular mass. A high-performance technique was applied, using large gels (23 × 30 cm). Isoelectric focusing with anodic sample preparation and nonequilibrium running conditions (NEPHGE) was combined with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in 15% acrylamide gels in the second dimension. The range of pI extends from pH 4.5 to 9.6. Seventy proteins were identified by combinations of amino acid analysis, N-terminal and internal sequencing, immunostaining, matrix assisted laser desorption/ionization-mass spectrometry (MALDI-MS) peptide mass fingerprinting, post-source decay MALDI-MS and ladder sequencing by carboxypeptidase P. The identification of additional proteins, not found in the master gel, was achieved by immunoblotting. Unequivocal identification with high sensitivity and good yield was obtained by combining internal sequencing and MALDI-MS. In-gel digestion, the concentration and purification of peptides in a peptide collecting device, and the improved FRAGMOD program for peptide mass fingerprinting have added to the security and sensitivity of identification. The high-performance human myocardial 2-DE database was built up with proteins detected by the TOPSPOT program. Spots within six sections of the whole pattern are clickable. Protein description includes detailed information about identification, characterization, and links to the related SWISS-PROT, other 2-DE databases and Medline entries. The database is constructed in accordance with four of the rules for a federated database.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Rapid Communications 13 (1992), S. 289-298 
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 96 (1963), S. 2894-2898 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis-trichlorsilyl-dichlormethan und Tris-trichlorsilyl-chlormethan, zwei der möglichen Zwischenverbindungen bei der Reaktion von Silicium-Kupfer-Gemischen mit Tetrachlorkohlenstoff, wurden mit jenen ebenfalls umgesetzt. Die isolierten Reaktionsprodukte bestätigten den seinerzeit angenommenen, schrittweisen Ersatz der an Kohlenstoff gebundenen Chloratome durch Trichlorsilylgruppen. Daneben lief stets eine Dechlorierung ab, die höheren Temperaturen außer-dem von einer Pyrolyse begleitet war. Verbindungen, die diesen Nebenreaktionen entstammen, wurden isoliert.
    Additional Material: 3 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 87-91 
    ISSN: 1434-1948
    Keywords: Imido complexes ; Titanium ; Heteroallylic ligands ; Benzamidinate ligands ; Diiminophosphinate ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of Ti(NtBu)Cl2(py)2 (1, py = pyridine) with bulky heteroallylic ligands in a 1:1 molar ratio affords the monosubstituted derivatives [PhC(NSiMe3)2]Ti(NtBu)Cl(py)2 (2), [MeOC6H4C(NSiMe3)2]Ti(NtBu)Cl(py) (3), and [Ph2P(NSiMe3)2]Ti(NtBu)Cl(py) (4). Similarly, 2:1 reactions afforded the disubstitution products [PhC(NiPr)2]2Ti(NtBu)(py) (6) and [Ph2P(NSiMe3)2]2Ti(NtBu) (7). The bis(pyridine) adduct Ph2P(NSiMe3)2Li(py)2 (5) was isolated as a by-product during the preparation of 4. The molecular structures of 7 has been established by X-ray crystallography.
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  • 10
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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