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  • Chemistry  (189)
  • Analytical Chemistry and Spectroscopy  (8)
  • Lunar and Planetary Science and Exploration  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Stereoselective polymerization of butadiene by a new dicationic nickel complex (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 239 (1996), S. 33-41 
    Details
    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: Der neuartige dikationische Komplex [dppfNi(MeCN)4][BF4]2 (dppf = 1,1′-Bis(diphenylphosphin)ferrocen) zeigte in Anwesenheit von Diethylaluminiumchlorid (AIEt2CI) hohe Aktivität für die Polymerisation von 1,3-Butadien. Reaktionsdauer, Temperatur und das Aluminium/Nickel-Verhältnis wurden auf maximale Aktivität und Selektivität optimiert. Umsätze über 90% konnten erreicht werden. Im Vergleich zu Polybutadienen, die mit anderen Nickel-Phosphin-Systemen hergestellt wurden, zeigten die synthetisierten Polybutadiene höhere cis-1,4-Anteile (〈80%) und eine geringe Bildung von 1,2-Einheiten (2%). Alle Polymeren hatten niedrige mittlere Molekulargewichte (Mw 〉 11 800).
    Notes: The new dicationic nickel complex [dppfNi(MeCN)4][BF4]2 (dppf = 1,1′-bis(diphenylphosphino)ferrocene) in the presence of diethylaluminium chloride (AIEt2CI) exhibited high activity on the 1,3-butadiene polymerization. Reaction time, temperature and aluminium/nickel molar ratio were optimized in order to achieve maximum activity and selectivity. Conversions higher than 90% were obtained in contrast to other nickel-based systems using phosphine ligands, the resulting polybutadiene showed high cis-1,4 (〈80%) content and only small amount of 1,2-units (2%). All polymers presented low molecular weights (Mw 〉 11 800).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052390104
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  • 2
    Electronic Resource
    Electronic Resource
    Application of thin film dialysis to the determination of equilibrium constants (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 837-842 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A theoretical basis for thin-film dialysis involving binding between a ligand and nondialyzing species is presented. A general differential equation that applies to the case of equivalent, noninteracting sites is derived relating [A]F, [A]T, [P]T, and K. Numerical solutions to this equation are used to develop a series of escape curves corresponding to specific values of the parameters [P]T, [A]i, K, and k0. A general method for determining an equilibrium binding constant from thin-film dialysis data is given. A comparison of thin-film dialysis results predicted by this theory with literature data shows essential agreement.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170403
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  • 3
    Electronic Resource
    Electronic Resource
    Complexity of the hydrolytic degradation of aliphatic polyesters (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 247 (1997), S. 239-253 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Aliphatic polyesters are more or less hydrolytically degradable, depending on their chemical, configurational and morphological structures. Hydrolysis can be either homogeneous or heterogeneous, depending on many structural and environmental factors. The present understanding of this hydrolytic degradation is recalled. The importance of diffusion-reaction phenomena is discussed on the basis of the behaviors of polyesters derived from α-hydroxy acids, namely lactic and glycolic acids and attempts are made to extend the understanding to other members of the aliphatic polyester family. The main results of some recent investigations of the effects on poly(lactic acid) polymers of basic additives and of initiators such as stannous octoate and zinc metal, which are now industrially used, are presented.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052470116
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  • 4
    Electronic Resource
    Electronic Resource
    Binding of alcohols to the peptide CO-group of poly-L-proline in the I and II conformation. I. Demonstration of the binding by infrared spectroscopy and optical rotatory dispersion (1969)
    New York : Wiley-Blackwell
    Biopolymers 8 (1969), S. 237-246 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding of n-butanol, benzyl alcohol, and trifluoroethanol to polyproline I (all peptide bonds in cis configuration) and II (all peptide bonds in trans configuration) has been demonstrated. It was found by infrared spectroscopy that hydrogen bonds are formed between the CO groups of the polymer and the OH groups of the alcohols. Their strength increases from n-butanol via benzyl alcohol to trifluoroethanol. The binding of benzyl alcohol could also be followed by optical rotatory dispersion due to the fact that the electronic transitions of the benzyl ring are rendered optically active by the binding to the polymer.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1969.360080209
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  • 5
    Electronic Resource
    Electronic Resource
    A cooperative transition between two helical conformations in a linear system: poly-L-proline I ⇌ II. II. Kinetic studies (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 721-737 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational transition between the two helical forms I and II of poly-L-proline serves as an experimental model for the study of the kinetic, behavior of cooperative systems. The slow I ⇌ II conversion after a sudden perturbation of the solvent composition was followed polarimetrically. The dependence of the mean relaxation times on chain length and the degree of conversion was compared with Schwarz's theory. In addition, a description of the entire relaxation curves was possible in three special cases: all-or-nothing, small perturbations of the I ⇌ II equilibrium in long chains, and conversions which start off with molecules completely in one or the other conformational state. The mathematical model on which the theory is based contains only one more adjustable parameter than the equilibrium model, but it adapts to the experimental results surprisingly well. The present kinetic results and equilibrium measurements on this system are described by the same values of those parameters which are common to both models. The found value of the rate constant of the propagation step, i.e. the cis ⇌ trans isomerization of a peptide bond at an existing I-II junction, agrees with the rate of isomerization in N,N-dimethylacetamide reported in the literature. The rate of nucleation is up to 105 times smaller than the rate of propagation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360100410
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  • 6
    Electronic Resource
    Electronic Resource
    Isochinoline, II. 3.3-Dialkylsubstituierte 3.4-Dihydro-isochinoline aus Alkyl-aryl-cyclopropanen (1971)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 104 (1971), S. 248-258 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Isoquinolines, II. 3.3-Dialkyl-3.4-dihydroisoquinolines from Alkyl-aryl-cyclopropanesUnder the conditions of the Graf-Ritter reaction alkyl-aryl-cyclopropanes 8 react with nitriles 2 via dialkyl-benzyl-carbonium ions 1 to give 3.3-dialkyl-3.4-dihydroisoquinolines 3. The effect of the substituents R1, R2, and R3 in 8 on the reaction is discussed.
    Notes: Alkyl-aryl-cyclopropane 8 reagieren unter den Bedingungen der Graf-Ritter-Reaktion über Dialkyl-benzyl-carboniumionen 1 mit Nitrilen 2 zu 3.3-dialkylsubstituierten 3.4-Dihydroisochinolinen 3. Der Einfluß der Substituenten R1, R2 und R3 in 8 auf den Reaktionsverlauf wird besprochen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19711040129
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  • 7
    Electronic Resource
    Electronic Resource
    Isochinoline,1. Synthese 3.3-dialkylsubstituierter 3.4-Dihydro- und 1.2.3.4-Tetrahydro-isochinoline (1970)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 103 (1970), S. 1674-1691 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Isoquinolines, 1. Synthesis of 3,3-Dialkyl Substituted 3,4-Dihydro- and 1,2,3,4-TetrahydroisoquinolinesDialkyl benzyl carbonium ions 12 react with nitriles under the conditions of the Graf-Ritter reaction to give 3,3-dialkyl-3,4-dihydroisoquinolines 9. 3,3-Dialkyl-1,2,3,4-tetrahydroisoquinolines 26 are prepared by reduction of dihydroisoquinolines as well as by Pictet-Spengler ring closure.
    Notes: Dialkyl-benzyl-carbonium-Ionen 12 reagieren mit Nitrilen unter den Bedingungen der Graf-Ritter-Reaktion zu 3.3-dialkylsubstituierten 3.4-Dihydro-isochinolinen 9. 3.3-Dialkylsubstituierte 1.2.3.4-Tetrahydro-isochinoline 26 lassen sich außer durch Reduktion entsprechender Dihydro-isochinoline auch durch Pictet-Spengler-Ringschluß darstellen.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19701030604
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  • 8
    Electronic Resource
    Electronic Resource
    Einige weitere Umsetzungen des 3.4-Dichlor-1.2.3.4-tetramethyl-cyclobutensX. Mitteil. über Cyclobutene; IX. Mitteil.: G. MAIER, Chem. Ber. 96, 2238 [1963]. (1963)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 96 (1963), S. 2362-2367 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Das Dichlorid I gibt bei der Thermolyse ein 1.4-Dichlor-tetramethylbutadien, das mit konz. Schwefelsäure Tetramethylfuran liefert. Beim Erhitzen mit Chinolin wird I unter Bildung des Chlordiens VI und des Triens IV dehydrohalogeniert. Aus dem Chlordien läßt sich durch Hydrogenolyse das äußerst reaktionsfähige Dien VIII gewinnen. Durch Chlorierung ergibt I ein Pentachlor-cyclobutan.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19630960913
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  • 9
    Electronic Resource
    Electronic Resource
    Valenzisomere des OctamethylcyclooctatetraensVIII. Mitteil. über Cyclobutene; I-VII. Mitteil. siehe Zitate. (1963)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 96 (1963), S. 2230-2237 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Thermolyse von Octamethyl-cyclooctatetraen (IV) oder eines der beiden stereoisomeren Tricyclooctadien-Derivate VI und VII bei Gegenwart von Alkali ergibt das permethylierte Bicyclo-[4.2.0]-octatrien (V). Dieses läßt sich selbst im Dunkeln in ein Endoperoxyd verwandeln und mit Silbernitrat oder mit Chinonen dehydrieren. Mit Säuren entstehen aus allen vier Valenzisomeren unter Verschiebung eines H-Atoms Strukturisomere mit semicyclischer Doppelbindung. Eines der tricyclischen Valenzisomeren ließ sich zum bekannten Dianhydrid der Tetramethylcyclobutan-tetracarbonsäure abbauen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19630960836
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  • 10
    Electronic Resource
    Electronic Resource
    Struktur der Sesquiterpene von Petasites hybridus (L.) G. M.et SCH.: Petasol- und Isopetasol-Abkömmlinge3. Mitt. über Petasites-Inhaltstoffe. 2.Mitt.: [1], Kurzmitt.: [2]. (1979)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 609-626 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structure of the Sesquiterpenes of Petasites hybridus (L.) G. M. et SCH.: Petasol and Isopetasol DerivativesThe structure of 11 compounds of the sesquiterpene fraction of petasites hybridus has been determined by combination of spectroscopic methods, especially by analysis of the 360-MHz-1H-NMR. spectra. Most natural products are esters of two isomeric sesquiterpene alcohols, characterized by an eremophilan skeleton, namely of petasol as well as of isopetasol. The structure of one key product has been confirmed by X-ray analysis.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19790620228
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