| Autor: |
Hofmann, Katja, Roth, Isabelle, Spange, Stefan |
| Zdroj: |
Macromolecular Chemistry & Physics; Aug2012, Vol. 213 Issue 16, p1655-1662, 8p |
| Abstrakt: |
The nucleophilic aromatic substitution (NAS) reaction of various fluoroaromatic/2,6- O-dimethyl- β-cyclodextrin complexes with poly(vinyl amine) (PVAm) has been studied in water at different pH. Increasing pH lowers the notable negative activation entropy of those types of NAS due to the PVAm chain segments becomes better accessible in basic media. At pH > 7, the zwitterionic intermediate in the course of NAS seems stabilized by intermolecular hydrogen bonds, which has an influence on the increase of activation energy for elimination the fluoride ion. As a consequence, the counter balance between activation entropy and activation energy determines the rate of the NAS with PVAm, which is shown for several functional fluoroaromatic compounds including fluoronitrobenzenes, fluoronitroanilines, and imine bases. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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