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  • 11
    Digitale Medien
    Digitale Medien
    A translactonization route to macrocyclic lactones (1977)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 99 (1977), S. 7359-7360 
    Details
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ja00464a047
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  • 12
    Digitale Medien
    Digitale Medien
    Mechanistic studies of carbonate macrocyclization (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 741-746 
    Details
    ISSN: 0887-624X
    Schlagwort(e): polymerization mechanism ; polymerization kinetics ; carbonate macrocyclization ; polycarbonate ; stopped-flow spectroscopy ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of phenylchloroformate (PCF) reactions have been used to model some of the key chemical events in carbonate macrocyclization. Three reactions have been studied using stopped-flow FT-IR spectroscopy: formation of acyl ammonium salt from PCF and three different trialkylamines, the conversion of acyl ammonium salt to urethane, and the condensation reaction between acyl ammonium salt and 4-isopropylphenol. The rate dependence was studied for triethylamine (TEA), diethylmethylamine (DEMA) and tri-n-butylamine (TBA) at 0°C in anhydrous CH2Cl2. The reactivity order for acyl ammonium salt formation for TBA: TEA: DEMA is 1 : 2.7 : 〉444. By contrast, condensation and urethane formation are not sensitive to the structure of the amine. The rate of condensation is comparable to the rate of acyl ammonium salt formation for TEA and TBA, while the rate of urethane formation is the slowest process for all three amines. These results are consistent with the view that the yield of macrocyclic polycarbonates is related to the concentration of the acyl ammonium salt. The optimum amine concentration for obtaining high yields of cyclics varies with the amine structure and parallels the difference in the rates of acyl ammonium salt formation. © 1994 John & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1994.080320412
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  • 13
    Digitale Medien
    Digitale Medien
    Rates of carbonate bond formation: Implications for macrocyclizationDedicated to Professor Maurice Morton to commemorate the establishment of the Maurice Morton Institute of Polymer Science at the University of Akron. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 33 (1994), S. 161-164 
    Details
    ISSN: 0959-8103
    Schlagwort(e): polymerization mechanism ; polymerization kinetics ; carbonate macrocyclization ; polycarbonate ; stopped-flow spectroscopy ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: High yields of cyclic oligomeric carbonates can be prepared using an amine-catalyzed reaction of bisphenol A-bischloroformate. We have studied the mechanistic aspets of this carbonate macrocyclization by the isolated study of key chemical events. Using stopped-flow FT-IR spectroscopy, we have found that the rate of carbonate formation between the intermediate acyl ammonium salt and 4-isopropylphenol is the same for the acyl ammonium salt derived from tri-n-butylamine, triethylamine and diethylmethylamine. Previously, we found that conversion of acyl ammonium salt to urethane was also insensitive to amine structure while the formation of acyl ammonium salt is profoundly dependent on amine structure. These results are consistent with a mechanism in which the selectivity toward macrocyclization versus linear oligomer or high polymer formation is related to acyl ammonium salt concentration.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pi.1994.210330206
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  • 14
    Digitale Medien
    Digitale Medien
    Preparation of bis(chloroformate)s for use in cyclization reactionsPresented at ‘MacroAkron '94, 35th IUPAC Symposium on Macromolecules Akron’, Ohio, 11-15 July 1994. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 37 (1995), S. 179-186 
    Details
    ISSN: 0959-8103
    Schlagwort(e): bis(chloroformate) ; cyclization ; interfacial condensation ; phosgene ; cyclic carbonate ; chloroformate ; bisphenol ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Cyclic oligomeric carbonates are prepared by a hydrolysis/condensation reaction from aromatic bis(chloroformate)s. Three methods for convenient preparation of bis(chloroformate)s have been developed: (1) use of diethylaniline to scavenge HCl, in a modification of an earlier procedure; (2) low pH, low temperature interfacial condensation of bisphenols with phosgene; and (3) use of Ca(OH)2 in interfacial condensation with phosgene. Reaction parameters which control formation of monomeric bis(chloroformate)s versus higher oligomerization include temperature, pH, and rate of phosgene addition. For water-soluble bisphenols such as hydroquinone, the phase ratio of water to CH2Cl2 can also be important.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pi.1995.210370305
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  • 15
    Digitale Medien
    Digitale Medien
    Stopped-flow fourier transform infrared studies in polymer chemistry (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1249-1272 
    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 application of stopped-flow FT-IR spectroscopy to group transfer polymerization (GTP) and cyclic oligomeric carbonate formation is described. The influence of catalyst structure, propagating end stereochemistry and degree of polymerization (DP) on the rate of monomer addition was examined for GTP. Also, the major GTP termination process was identified and characterized. Model reactions were used to study the kinetics of acyl ammonium salt formation and subsequent conversion to urethane. These results were used to further develop the mechanism of bisphenol A-bischloroformate macrocyclization.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1993.021940501
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