ISSN:
0025-116X
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
The cationic ring-opening polymerization of 1-azabicyclo[4.2.0]octane (1) was studied with initiators providing small and large anions, namely F⊖, Br⊖, I⊖, picryl(Pic⊖), CF3SO3⊖. In nitrobenzene as solvent the macroions and macroion-pairs, independently of the anion size, propagate with the same rate constant kp+ = kp± = 7,0 · 10-3 mol-1 · l · S-1 at 35°C ( Δ HP≠ = 55 ± 5kj· mol-1, Δ SP≠ = 105 ± 11 j · mol-1 · K-1). This result strongly indicates that it is not the large size of anoins which is exclusively responsible for the equality kP+ = kP±. The structure of the onium ions, their strong solvation, and the resulting weak interactions with anions are primarily responsible for the observed equalities. In methanol as solvent polymerization proceeds 30 times slowlier than in nitrobenzene and ion-pairs are more reactive by 40% than ions, in agreement with Enikolopyan's findings.
Zusätzliches Material:
9 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/macp.1984.021850106
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