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  • 1
    Electronic Resource
    Electronic Resource
    Thermisch und UV-photochemisch initiierte hochdruckpolymerisation des ethylens, 2Teil 1: cf.1. Molmassen-verteilung (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1699-1717 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molar mass distribution of polyethylenes synthesized at pressures up to 2500 bar and temperatures to 255°C with thermal and partly with photochemical initiation is determined by GPC. In the limiting situation of high pressure, low temperature, and small conversion a distribution function based on a limited set of kinetic equations provides a fair representation of the experimental data. The transfer constant with the monomer is derived as a function of pressure and temperature. The logarithmic normal distribution reasonably represents the molar mass distribution of the high pressure polyethylenes if the conversion is low and if both empirical parameters are taken as temperature dependent. The degree of long chain branching is analyzed for the ethylene polymerization as a function of pressure and temperature and to maximum conversions of 30%. It turns out that even at conversions as low as 2% long chain branching is not negligible.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850817
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  • 2
    Electronic Resource
    Electronic Resource
    Etude 13C NMR d'alcanes ramifiés, 1. n-alkyl-12 tricosanes. Application aux polyéthylènes basses densités (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 2305-2320 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series (8 compounds) of mono-branched alkanes (12-n-alkyl-tricosanes) as models for polyethylene was prepared. The results obtained from 13C NMR show in particular the dependence of the chemical shifts (Δδ ≈ 0,05 p.p.m.) on T in the temperature range 37°C ≤ T ≤ 100°C but that the branches remain identifiable in this range of temperature. By mixing different tricosanes we simulated various branched polyethylenes. The chemical shifts observed at 100°C with some corrections complete the incremental system of Grant and Paul as modified by Randall for the effect of temperature.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021820820
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  • 3
    Electronic Resource
    Electronic Resource
    Etude par 13C NMR d'alcanes lourds mono- et diramifiés. Modèles de polyoléfines (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 569-583 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 13C NMR spectra were obtained for a series of branched, heavy alkanes at 37°C and 100°C, which provide a model set for describing the branched sequences in low density polyethylene (LDPE) and copolymers of α-olefines. In addition, they provide a model set for revising the empirical Grant-Paul and Lindeman-Adams additive coefficients and corrective terms for pre-dicting 13C chemical shifts of alkanes. The resulting revised parameters (for 37°C and 100°C) produce more accurate predictions of 13C NMR spectra for branched alkanes and it is noted that some corrective terms can be temperature-sensitive.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1983.021840312
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  • 4
    Electronic Resource
    Electronic Resource
    Thermisch und UV-photochemisch initiierte hochdruckpolymerisation des ethylens, 1. Molmassen-mittelwerte (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1685-1697 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ethylene is polymerized with thermal and with UV-photochemical initiation at temperatures between 130°C and 255°C up to pressures of 2500 bar. The conversions are between two and five percent. The degrees of polymerization as obtained from viscosity experiments are dependent on reaction temperature and pressure, but are insensitive to the kind of initiation, thermal or photochemical. These observations are explained by an equation which relates the degree of polymerization to kinetic parameters of the system which have partly been determined by independent experiments. From this equation, the activation energy and the activation volume of the transfer constant with the monomer, cm, are determined to be Ea(cm) = 43,9 ± 4 kJ · mol-1 and ΔV≠ (cm)=20,1 ± 3 cm3 · mol-1, respectively.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850816
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  • 5
    Electronic Resource
    Electronic Resource
    Tetrapyrrol-Biosynthese, 10. Einfache biomimetische Porphyrin-Synthesen (1980)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1980 (1980), S. 263-274 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Tetrapyrrole Biosynthesis, 101).  -  Easy Biomimetic Porphyrin SynthesesThe hitherto unknown porphyrin octacarboxylic acids 12a and 20a can be prepared in a highly selective reaction by acid catalysed condensation of monopyrroles, which are structurally related to porphobilinogen (1), the precursor of porphyrin biosynthesis. The 7-step synthesis of 12b (average yield per step 68%) provides a particulary facile entry to a porphyrin with promising properties as a model compound. The porphyrinogenes corresponding to 12a and 20a differ from the biologically important uroporphyrinogen III (13) only by absence or presence of four CH2 groups each.
    Notes: Durch säurekatalysierte Kondensation einfacher Monopyrrole, die der Porphyrin-Biosynthesevorstufe Porphobilinogen (1) strukturverwandt sind, lassen sich in hochselektiver Reaktion die bisher unbekannten Porphyrinoctacarbonsäuren 12a und 20a darstellen. Die Siebenstufen-Synthese von 12b (durchschnittliche Ausbeute je Stufe 68%) ermöglicht einen besonders einfachen Zugang zu einem Porphyrin mit günstigen Eigenschaften als Modellverbindung. Die 12a und 20a entsprechenden Porphyrinogene unterscheiden sich vom biologisch wichtigen Uroporphyrinogen III (13) nur durch Mehrgehalt bzw. Mindergehalt von je vier CH2-Gruppen.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198019800212
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  • 6
    Electronic Resource
    Electronic Resource
    Tetrapyrrol-Biosynthese, 13. Synthese linearer Di-, Tri-, Tetra- und Pentapyrrole mit natürlichen Seitenketten und günstigen Eigenschaften (1982)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1982 (1982), S. 1261-1271 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Tetrapyrrole Biosynthesis, 131).  -  Synthesis of Linear Di-, Tri-, Tetra-, and Pentapyrroles with Natural Side Chains and Favourable PropertiesBy application of a substantially simplifying synthetic conception which avoids the conventional use of ester protective groups, the even-numbered (12, 15) and odd-numbered oligopyrrols (17, 19) were prepared from the monopyrrole 4. These oligopyrroles owe favourable condensation and solubility properties to their propionic acid side chains  -  which are also present in natural products containing pyrrole  -  and are useful model compounds.
    Notes: Mit Hilfe eines stark vereinfachten Synthesekonzepts, das die konventionelle Anwendung von Esterschutzgruppen vermeidet, wurden die geradzahligen (12, 15) und ungeradzahligen Oligopyrrole (17, 19) aus dem Monopyrrol 4 erstmalig dargestellt. Diese Oligopyrrole verdanken ihren  -  auch in Pyrrol-Naturstoffen enthaltenen  -  Propionsäureseitenketten günstige Kondensations-und Löslichkeitseigenschaften und stellen nützliche Modellverbindungen dar.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198219820704
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  • 7
    Electronic Resource
    Electronic Resource
    Tetrapyrrol-Biosynthese, 14. Extrem selektive Porphyrin-Bildung bei der Cyclisierung verschiedener Oligopyrrole (1982)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1982 (1982), S. 1272-1279 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Tetrapyrrole Biosynthesis, 141).  -  Extremely Selective Porphyrin Formation by Cyclization of Different OligopyrrolesIn order to gain insight into the formation tendency of porphyrins, the acid catalysed condensation of the linear oligopyrroles 12-d, 18, and 19 was investigated in several combinations. Although the formation of cyclic tetra-, penta-, hexa-, and heptapyrroles might in principle be possible herewith, only cyclization to the porphyrin 13 under elimination of monopyrrole units took place in every case. This remarkable behaviour of the oligopyrroles is caused by their favoured helical conformation, which always forces their cyclization to the porphyrin system.
    Notes: Um Einblick in die Bildungstendenz der Porphyrine zu gewinnen, wurde die säurekatalysierte Kondensation linearer Oligopyrrole 12a-d, 18 und 19 in verschiedenen Kombinationen untersucht. Obwohl hierbei im Prinzip die Bildung cyclischer Tetra-, Penta-, Hexa- und Heptapyrrole möglich wäre, erfolgte in jedem Falle Cyclisierung zum Porphyrin 13 unter Eliminierung von Monopyrrol-Einheiten. Ursache für dieses bemerkenswerte Verhalten der Oligopyrrole ist deren begünstigte helikale Konformation, die stets den Ringschluß zum Porphyrin-Grundgerüst erzwingt.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198219820705
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  • 8
    Electronic Resource
    Electronic Resource
    Pilzinhaltstoffe, 32. Nachweis einer bicyclischen Zwischenstufe der Anthrachinon-Biosynthese (1981)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1981 (1981), S. 2106-2116 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Natural Products from Fungi, 321).  -  Detection of a Bicyclic Intermediate of Anthraquinone BiosynthesisFeeding of the synthetically 14C-labelled diketonaphthol 4a to surface cultures of the mould fungus Penicillium islandicum yielded radioactive islandicin (5d) and skyrin (12) with significant incorporation rates. Thus the participation of a bicyclic intermediate in anthraquinone biosynthesis by microorganisms has been detected for the first time.
    Notes: Verfütterung des synthetisch 14C-markierten Diketonaphthols 4a an Oberflächenkulturen des Schimmelpilzes Penicillium islandicum ergab mit signifikanten Einbauraten radioaktives Islandicin (5d) und Skyrin (12). Damit wurde erstmalig die Beteiligung einer bicyclischen Zwischenstufe an der Anthrachinon-Biosynthese durch Mikroorganismen nachgewiesen.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198119811204
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  • 9
    Electronic Resource
    Electronic Resource
    Tetrapyrrol-Biosynthese, 9. Synthese von geschütztem Nor- und Homoporphobilinogen (1980)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1980 (1980), S. 253-262 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Tetrapyrrole Biosynthesis, 91).  -  Synthesis of Protected Nor- and HomoporphobilinogenThe monopyrroles norporphobilinogen (3) and homoporphobilinogen (4), being derivatives of the biogenetic porphyrin precursor porphobilinogen (1), are of topical interest for biomimetic porphyrin syntheses. Syntheses were developed for the protected “depot compounds” 6a und 7a from which the highly reactive, previously unknown species 3 and 4 may be liberated by alkaline hydrolysis for subsequent condensation as occasion demands.
    Notes: Die Monopyrrole Norporphobilinogen (3) und Homoporphobilinogen (4) besitzen als Derivate der Porphyrin-Biosynthesevorstufe Porphobilinogen (1) aktuelles Interesse für biomimetische Porphyrin-Synthesen. Es wurden Synthesen für die geschützten “Depotverbindungen” 6a und 7a entwickelt, aus denen die hochreaktiven, zuvor unbekannten Verbindungen 3 und 4 nach Bedarf durch alkalische Hydrolyse für anschließende Kondensationen frei gesetzt werden können.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198019800211
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  • 10
    Electronic Resource
    Electronic Resource
    Dynamic 13C NMR study of the cyclohexane ring in spirocyclohexanes (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 14 (1980), S. 451-454 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A dynamic study of spirocyclohexanes was carried out using low-temperature 13C nuclear magnetic resonance spectroscopy. The variations of the energy barrier to inversion of the cyclohexane ring are interpreted in terms of the electronegativity of the heteroatoms of the spiro substituent.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270140606
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