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  • Artikel  (51)
  • Chemistry  (49)
  • Biochemistry and Biotechnology  (7)
  • Cloning, Molecular  (2)
  • 1985-1989  (51)
  • 1
    Digitale Medien
    Digitale Medien
    Reaction of poly(vinyl alcohol) with n-butyl isocyanate. Chemical hydrolysis of the resulting polymers (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 152 (1987), S. 79-91 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Diese Untersuchung befaßt sich mit einigen kinetischen Merkmalen der Reaktion von n-Butylisocyanat mit Polyvinylalkohol ohne jeden Katalysator und unter Verwendung von Triethylendiamin als Katalysator. Die Struktur der resultierenden Polymeren wurde mit Hilfe der IR-, 1H-, und 13C-NMR-Spektroskopie und chemischer Analyse ermittelt. Es wurden Vinylalkohol-Vinylbutylurethancopolymere (VAL-VBU) erhalten. Es ergab sich eine lineare Abhängigkeit der Reaktionsgeschwindigkeit von Polymer-, n-Butylisocyanat- und Triethylendiaminkonzentration. Die Reaktionsgeschwindigkeitskonstante nimmt mit zunehmender Reaktionszeit ab. Das kann mit der sterischen Hinderung durch die Urethangruppen, die entlang der Polymerkette eingebaut sind, erklärt werden. Die Aktivierungsenergie ergab sich zu 49,9 kJ/mol. Eine kinetische Untersuchung der homogenen Hydrolyse von VAL-VBU-Copolymeren wurde durchgefilhrt als Funktion der Basenkonzentration, der Temperatur und des VBU Gehalts. Es zeigte sich, daß die homogene Hydrolyse als Reaktion 1 . Ordnung verliluft, sowohl im Hinblick auf die Hydroxylionen als auch auf den VBU-Gehalt. Die Aktivierungsenergie filr die basenkatalysierte Hydrolyse betragt 79,3 kJ/mol. Die heterogene Hydrolyse von VAL-VBU-Copolymeren im basischen Medium zeigte, daß keine Hydrolyse unter diesen Bedingungen stattfand.
    Notizen: This study is concerned with some kinetic features of the reaction of n-butyl isocyanate with poly(vinyl alcohol) without any catalyst and using triethylene diamine as catalyst. The structure of the resulting polymers was determined by means of IR, 1H- and 13C-NMR spectroscopy as well as by chemical analysis. Vinyl alcohol-vinyl butyl urethane (VAL-VBU) copolymers were obtained. It has been found a linear dependence of reaction rate on polymer, n-butyl isocyanate, and triethylene diamine concentrations. Reaction rate constant decreases as reaction time increases. It can be explained by steric hindrance phenomena due to urethane groups incorporated along the polymeric chain. The activation energy was found to be 49.9 kJ/mol. A kinetic study of the homogeneous hydrolysis of VAL-VBU copolymers has been made as a function of the base concentration, the temperature, and the VBU content. The homogeneous hydrolysis was found to be first order with respect to both hydroxyl ion and VBU contents. The activation energy for the base catalyzed homogeneous hydrolysis was found to be 79.3 kJ/mol. The heterogeneous hydrolysis of VAL-VBU copolymers in basic medium showed that no hydrolysis takes place under the conditions employed.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051520108
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  • 2
    Digitale Medien
    Digitale Medien
    Nature et stabilité des complexes métalliques de cryptands dinucléants en solution. I. Polyazapolyoxa macrotricycle cylindrique et monocycle constitutif (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 456-464 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Nature and Stability of Some Metallic Complexes of Dinucleating Cryptands in Solution. I. A Polyazapolyoxa Cylindrical Macrotricycle and its Monocyclic SubunitpH-metry and UV spectrophotometry were used to study the complexing properties of the cylindrical macrotricycle, 1,7,13,19-tetraaza-4,16-dioxa-10,22,27,32-tetraoxatricyclo[17.5.5.5]tetratriacontane (1) and of its constitutive monocyclic subunit, 1,7-diaza-4,10-dioxacyclododecane (2) with some transition and heavy metal cations (Cu2+, Co2+, Ni2+, Zn2+, Cd2+, Pb2+, Ag+), in aqueous medium 0.1M Et4NClO4, at 25°. The protonation constants of the ligands as well as the nature and the stabilities of the complexes formed in the pH-regions studied were determined. The tricycle 1 only formed dinuclear M2L complexes with Cu2+, Zn2+, and Ag+, accompanied in the latter case by a protonated mononuclear MLH species, and with Cu2+ and Zn2+ at high pH-values by dinuclear hydroxo complexes. Only mononuclear complexes were evidenced with the other cations, ML being accompanied either by protonated or hydroxy mononuclear species. The mononuclear complexes of 1, when they existed, were more stable than the corresponding complexes of 2, except for cobalt which formed complexes of comparable stability with both ligands. In the other cases (Cd2+, Pb2+, Ag+), the stability differences between the complexes of 1 and 2 increased with the size of the cation.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19850680219
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  • 3
    Digitale Medien
    Digitale Medien
    Nature et stabilité des complexes métalliques de cryptands dinucléants en solution. III. Le monocycle [22]-Py2N4 (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 840-845 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Nature and Stability of Some Metallic Complexes of Dinucleating Cryptands in Solution III. The Monocycle [22]-Py2N4The nature and stability of complexes formed by a new 22-membered monocycle L = [22]-Py2N4 with the cations Mn+ = Cu2+, Co2+, Ni2+, Zn2+, Cd2+, Pb2+, and Ag+ have been determined in aqueous solutions (0.01M NaClO4, 25°) by pH-metry and also, for the copper system, by UV-absorption spectrophotometry. The stepwise protonation constants of the four amine functions of L were 9.1, 8.3, 7.1 and 3.7 logarithms units, respectively. No evidence was found for the protonation of the two pyridine nitrogen atoms. Mononuclear complexes MLn+ were identified in all systems investigated, but the dinuclear species M2L2n+ were only found with Cu2+ and Ag+. The logarithms of the overall stability constants for the copper and silver complexes are CuL2+, 12.9; Cu2L4+, 18.6; Agl+, 6.3; Ag2L2+, 10.9, respectively. Mononuclear hydroxy species MLOH(n-1)+ were identified in all systems except those of copper and silver. No dinuclear hydroxy complexes were detected. The complexing properties of L are compared to those of the large and less rigid bis-dien.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19850680404
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  • 4
    Digitale Medien
    Digitale Medien
    Water-insoluble dextrans by grafting, 2Part 1: cf.3.. Reaction of dextrans with n-alkyl chloroformates. Chemical and enzymatic hydrolysis (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 17-29 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: This work deals with the modification reaction of dextran with ethyl and butyl chloroformate using tertiary amines as catalyst/acceptor systems and the DMF/LiCl system as solvent. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy as well as by chemical analyses. The reaction rate was found to increase in the following order: N,N′-dimethylaniline 〈 pyridine 〈 triethylamine. The presence of cyclic carbonates was observed when triethylamine was used as catalyst. A linear dependence of the reaction rate on polymer and pyridine concentrations and a more complex dependence on the n-alkyl chloroformate concentration were found. Reaction rate and yield decrease with increasing amount of LiCl in the solvent medium and increase with increasing chain length of the n-alkyl chloroformate. The activation energy was found to be 64 kJ/mol (15,3 kcal/mol). The equilibrium water content (EWC) values decreases progressively when either the content of carbonate groups or the side chain length increases. The hydrolysis in the heterogeneous phase showed that the time required for the polymer solubilization is dependent upon the nature of the carbonate groups, the temperature as well as the pH value of the medium. Dextranase was found to be inactive in the hydrolysis of water-insoluble modified dextrans. However, the hydrolysis takes place when water-soluble modified dextrans were used.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1985.021860103
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  • 5
    Digitale Medien
    Digitale Medien
    Synthesis and hydrolysis of esters from amylose and nicotinoyl chloride (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 2269-2274 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The modification reaction of amylose with nicotinoyl chloride using pyridine as catalyst was studied. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy. A linear dependence of the reaction rate on polymer, nicotinoyl chloride and pyridine was found. The activation energy was found to be 32,2 kJ/mol. The hydrolysis in the heterogeneous phase showed that the release of the active compound is dependent upon the hydrophilic character of the modified amylose polymers, the temperature as well as the pH value of the medium.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1988.021891006
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  • 6
    Digitale Medien
    Digitale Medien
    Study of the distributions of chemical composition and molecular weight in relation to the preparation method of vinyl alcohol/vinyl acetate copolymers (1986)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 187 (1986), S. 1215-1228 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The chemical heterogeneity of two vinyl alcohol/vinyl acetate (VAL-VAC) copolymers prepared by partial acetylation of poly(vinyl alcohol) and by partial alkaline hydrolysis of poly(vinyl acetate), respectively, was studied by cross-fractionation. The used solvent/non-solvent systems were selected on the basis of cloud-point determinations. The chemical composition distribution (CCD) and the molecular weight distribution (MWD) curves were constructed from fractionation data. The observed chemical heterogeneity was correlated with the kinetic parameters of the two different methods used for the preparation of the VAL-VAC copolymers. Thus, squared standard deviation values \documentclass{article}\pagestyle{empty}\begin{document}$\overline {{\rm \sigma }^{2} }$\end{document}= 2,90·10-4 and \documentclass{article}\pagestyle{empty}\begin{document}$\overline {{\rm \sigma }^{2} }$\end{document}= 7,42·10-4 were found for the two VAL-VAC copolymers prepared by acetylation and hydrolysis, respectively. These results are in agreement with theoretical predictions. The cumulative data were fitted by the two-parameters MWD functions of Tung and of Wesslau.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1986.021870518
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  • 7
    Digitale Medien
    Digitale Medien
    Water-insoluble dextrans by grafting, 3Part 2: cf.2.. Reaction of dextran with butyl isocyanate. Chemical hydrolysis (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 2831-2838 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The modification reaction of dextran with butyl isocyanate using 1,4-diaza[2.2.2]bicyclooctane as catalyst was studied. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy as well as by chemical analysis. A linear dependence of the reaction rate on the concentrations of polymer, butyl isocyanate and catalyst was found. The activation energy was found to be 38,5 kJ/mol (9,2 kcal/mol). The homogeneous hydrolysis in alkaline medium was found to be first order with respect to both the base and the butyl urethane concentrations. The activation energy, obtained for the base catalyzed homogeneous hydrolysis, was 83,7 kJ/mol (20,0 kcal/mol). The heterogeneous hydrolysis of a water insoluble modified dextran (degree of substitution = 0,72) showed that no hydrolysis takes place under the applied conditions.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1987.021881205
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  • 8
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of 2-acetoxybenzoic acid-dextran ester conjugates (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 2391-2396 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: This work deals with the modification reaction of dextran with 2-acetoxybenzoyl chloride (acetylsalicyloyl chloride) using tertiary amines as catalyst/acceptor systems and the DMF/LiCl system as solvent. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy. Transesterification reactions were observed when 4-dimethylaminopyridine or pyridine were used as catalysts, with the formation of acetoxy, 2-hydroxybenzoyloxy (salicyloyloxy) and 2-acetoxybenzoyloxy (acetylsalicyloxy) groups. When triethylamine was used as catalyst, only acetylsalicyloyloxy groups were found to be grafted onto the polymer chain. A linear dependence of the reaction rate on the concentrations of polymer, acetylsalicyloyl chloride and triethylamine was found. The activation energy was found to be 13,8 kJ/mol.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1989.021901005
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  • 9
    Digitale Medien
    Digitale Medien
    Release of sodium salicylate from vinyl alcohol/n-alkyl vinyl carbonate copolymers (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 2117-2123 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: This study is concerned with the sodium salicylate release from thin discs of vinyl alcohol/n-alkyl vinyl carbonate copolymers into an aqueous medium under sink conditions. The drug content of the disc decreases with pseudo-first order rate initially, whereas the drug quantity released is proportional to the square root of time. Data analysis supported the latter treatment, which is in agreement with the diffusional matrix model and invalidates the pseudo-first order assumption. The diffusion coefficient D of vinyl alcohol/ethyl vinyl carbonate copolymers decreases with increasing ethyl vinyl carbonate content whilst D increases as both sodium salicylate concentration and temperature increase. The activation energy of diffusion was found to be 46,03 kJ/mol (11,00 kcal/mol).
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1985.021861015
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  • 10
    Digitale Medien
    Digitale Medien
    Crystallization, melting and morphology of poly(hexamethylene sulfide) (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 1205-1215 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Poly(hexamethylene sulfide) fractions, ranging in molecular weight from 4600 to 20000, were isothermally crystallized from the melt state in the temperature range 50-70°C. The dependence of the melting temperature on the crystallization temperature was analyzed in experiments involving low and high levels of crystallinity. The equilibrium melting temperature corresponds to 366 K and the enthalpy of fusion was found to be 40,5 cal/g (= 170 J/g). The isothermal overall crystallization rates were analyzed using dilatometric and calorimetric techniques. The Avrami exponent is an integral value, n = 3, and the crystallinity varies with increasing molecular weight from 65% to 55%. The morphology is spherulitic and it was found that the growth rate is linear in the whole range of crystallization temperatures. The temperature coefficient of the crystallization was analyzed using nucleation theory, and comparison between dilatometric and growth data revealed that the overall rate and growth rate-temperature coefficients are approximately equal.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1987.021880523
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