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  • 1
    Electronic Resource
    Electronic Resource
    Polymerization of transdimethylthiirane with chiral initiators (1979)
    Springer
    Polymer bulletin 1 (1979), S. 267-273 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In the polymerization of transdimethylthiirane using a chiral initiator an unusual phenomenon was observed : the sign of unreacted monomer changed at high conversions. A new kinetic equation is proposed to explain this behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00254335
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  • 2
    Electronic Resource
    Electronic Resource
    13C NMR study of the tacticity of poly(propylene oxide)s prepared by polymerization with α,β,γ,δ-tetraphenylporphyrin/AlEt2Cl as initiator system: An example of first-order markovian statistics in ring-opening polymerization (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 637-650 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Racemic and enantiomerically enriched poly(propylene oxide)s were prepared using α, β, γ, δ-tetraphenylporphyrin/AlEt2Cl as initiator system. Triad tacticity of the polymers was analyzed by 13C NMR spectroscopy (62,89 MHz). A predominance of isotactic triads was observed in the case of the racemic polymer, corresponding to a non-random distribution of configurational units in the polymer chain. A model correlating tacticity with enantiomeric excess of starting monomer in the case of a first-order Markovian distribution was established. Good agreement between experimental results and calculated triad contents (according to the model previously described) was observed for enantiomerically enriched polymers. This indicates a steric control by the last unit of the growing chain end. The influence of the size of the substituent was examined for the case of poly(1,2-epoxybutane). The origin of the chain-end effect is discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1988.021890316
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  • 3
    Electronic Resource
    Electronic Resource
    Asymmetric synthesis polymerization of meso oxiranes and thiiranesThis work is dedicated to the memory of Professor Piero Pino. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 295-299 
    Details
    ISSN: 0899-0042
    Keywords: cis-dimethylthiirane ; cyclohexene sulfide ; cis-dimethyloxirane ; cyclohexene oxide ; chiral initiator system ; enantiogenic polymerization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The asymmetric synthesis polymerization or “enantiogenic” polymerization of some meso oxiranes, cis-dimethyloxirane (cis-DMO) and cyclohexene oxide (CHO), and thiiranes, cis-dimethylthiirane (cis-DMT) and cyclohexene sulfide (CHS), initiated with different chiral systems was examined. Strong differences in behaviour were observed between oxiranes and thiiranes depending on the initiator used. The initiators based on ZnEt2 or CdMe2 and a chiral diol give optically active polymers from meso thiiranes but fail to induce an asymmetric polymer synthesis with meso oxiranes. A new chiral initiator based on ZnEt2 and (1S,2R)-ephedrine allowed us to prepare optically active poly CHOs, which can be fractionated into fractions exhibiting opposite optical activities. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040506
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  • 4
    Electronic Resource
    Electronic Resource
    Configurational rules governing the stereochemical control of chiral initiators in ring-opening polymerizations of heterocyclic monomers (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 3089-3099 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Configuration rules were established for the polymerization of cyclic monomers with chiral initiators. The latter recognize in the monomer an asymmetric carbon of homochiral configuration. The chirality of the initiator is defined by the “local” asymmetry of the ligand and by the overall asymmetry of the particular arrangement of catalytic aggregates. Two types of process called “homosteric” and “antisteric,” which apply to the polymerization of resolvable monomers and achiral monomers of meso structure, are defined. These configurational rules have a general character and are verified in many examples of differently substituted three- or four-membered cyclic monomers (oxiranes, thiiranes, β-lactones). Stereoelective polymerization appears to be an original method for the determination of the absolute configuration of some monomers of unknown chirality.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.170181018
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