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Monomer versus Alcohol Activation in the 4‐Dimethylaminopyridine‐Catalyzed Ring‐Opening Polymerization of Lactide and Lactic O ‐Carboxylic Anhydride
Author(s) -
Bonduelle Colin,
MartínVaca Blanca,
Cossío Fernando P.,
Bourissou Didier
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200800346
Subject(s) - chemistry , ring opening polymerization , catalysis , monomer , polymer chemistry , lactide , polymerization , bifunctional , nucleophile , ring (chemistry) , acetic anhydride , alcohol , organic chemistry , medicinal chemistry , polymer
Model reactions for the 4‐dimethylaminopyridine (DMAP)‐catalyzed ring‐opening polymerization of lactide and the corresponding lactic O ‐carboxylic anhydride (lacOCA) have been studied computationally at the B3LYP/6–31G(d) level of theory. The solvent effect of dichloromethane was taken into account through PCM/SCRF single‐point calculations at the B3LYP/6–31G(d) level of theory. In marked contrast with that predicted for the reaction of alcohols with acetic anhydride, the mechanism in which nucleophilic activation of the monomer involving acylpyridinium intermediates was found to be energetically less favorable than the base activation of the alcohol through hydrogen bonding. The concerted pathway for the ring‐opening of lactide and lacOCA was shown to compete with the traditional stepwise mechanism involving tetrahedral intermediates. Furthermore, DMAP is proposed to act as a bifunctional catalyst through its basic nitrogen center and an acidic ortho ‐hydrogen atom.