Roles of Monomer Binding and Alkoxide Nucleophilicity in Aluminum-Catalyzed Polymerization of ε-Caprolactone
Citations Over TimeTop 10% of 2012 papers
Abstract
The kinetics of polymerization of ε-caprolactone (CL) initiated by aluminum-alkoxide complexes supported by the dianionic forms of N,N-bis[methyl-(2-hydroxy-3-tert-butyl-5-R-phenyl)]-N,N-dimethylethylenediamines, (LR)Al(Oi-Pr) (R = OMe, Br, NO2) were studied. The ligands are sterically similar but have variable electron donating characteristics due to the differing remote (para) ligand substituents R. Saturation kinetics were observed using [CL]0 = 2–2.6 M and [complex]0 = 7 mM, enabling independent determination of the substrate coordination (Keq) and insertion (k2) events in the ring-opening polymerization process. Analysis of the effects of the substituent R as a function of temperature on both Keq and k2 yielded thermodynamic parameters for these steps. The rate constant k2, related to alkoxide nucleophilicity, was strongly enhanced by electron-donating R substituents, but the binding parameter Keq is invariant as a function of ligand electronic properties. Density functional calculations provide atomic-level detail for the structures of key reaction intermediates and their associated thermochemistries.
Related Papers
- → Effect of substituent on the UV-Vis spectra: an extension from disubstituted to multi-substituted benzylideneanilines(2016)18 cited
- → PS II inhibitory activity of 2,4-diamino-6-chloro-s-triazines with a chiral sec-butyl and/or .ALPHA.-methylbenzyl group.(1990)15 cited
- → Proximity effects in pyridines. Proton chemical shifts in substituted methyl pyridinecarboxylates(1975)18 cited
- → The origin and nature of the π-electron steric effect(1977)2 cited
- → PSII Inhibitory Activity of 2,4-Diamino-6-chloro-s-triazines with a Chiralsec-Butyl and/or α-Methylbenzyl Group(1990)1 cited