Premium
Delocalized π‐electrons in 2‐oxazoline rings resulting in negatively charged nitrogen atoms: revealing the selectivity during the initiation of cationic ring‐opening polymerizations
Author(s) -
Bodner Thomas,
Ellmaier Lisa,
Schenk Verena,
Albering Jörg,
Wiesbrock Frank
Publication year - 2011
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.3126
Subject(s) - delocalized electron , oxazoline , cationic polymerization , ring (chemistry) , chemistry , crystallography , atom (system on chip) , electrophile , aromaticity , regioselectivity , photochemistry , polymer chemistry , organic chemistry , molecule , catalysis , computer science , embedded system
Abstract The inventory of the single‐crystal X‐ray structures of aliphatic and aromatic 2‐oxazolines, namely 2‐nonyl‐2‐oxazoline, 2,2′‐tetramethylenebis(2‐oxazoline) and 2‐phenyl‐2‐oxazoline, reveals significant delocalization of π‐electrons along the NCO segment. The delocalization of π‐electrons is stabilized by inductive and resonance contributions of the side‐chains; in 2‐phenyl‐2‐oxazoline, also π‐arene interactions between the benzene ring and the CN and the CO bond stabilize the crystalline phase. This delocalization gives a partial negative charge to the nitrogen atom and a partial positive charge to the oxygen atom. The partial negative charge of the nitrogen atom makes this atom the exclusive reaction partner also for highly reactive non‐selective cations, which explains the regioselectivity of electrophilic attacks in cationic ring‐opening polymerizations. Copyright © 2011 Society of Chemical Industry