Mechanism of halogen exchange in ATRP
Journal
Macromolecules
Journal Volume
44
Journal Issue
19
Pages
7546-7557
Date Issued
2011
Author(s)
Abstract
Detailed mechanistic studies reveal that halogen exchange (HE) in ATRP can occur not only by a radical pathway (atom transfer) but also by an ionic pathway (SN2 reaction) because Cu(I)(L)X and Cu (II)(L)X2 complexes contain weakly associated halide anion that can participate in the SN2 reaction with alkyl halide (ATRP initiator). Both pathways were kinetically studied, and their contributions to the HE process were quantitatively evaluated for seven alkyl halides and three Cu(I)(L)Cl complexes. Radical pathway dominates the HE process for 3 and 2 alkyl bromides with more active complexes such as Cu (I)(TPMA)Cl. Interestingly, ionic pathway dominates for 1 alkyl bromides and less active ATRP catalysts. These studies also revealed that degree of association of alkyl halide anion depends on the structure of copper complexes. In addition, radical pathway is accompanied by the reverse reactions such as deactivation of radicals to alkyl bromides and also activation of alkyl chlorides, reducing the efficiency of halogen exchange. ? 2011 American Chemical Society.
SDGs
Other Subjects
Active complexes;Alkyl bromides;Alkyl chlorides;Alkyl halides;As deactivation;Atom transfer;ATRP initiator;Copper complexes;Degree of association;Halide anions;Halogen exchange;Ionic pathways;Mechanistic studies;Radical pathway;Reverse reactions;Bromine compounds;Chlorine;Chlorine compounds;Copper compounds;Free radical reactions;Ion exchange;Iodine
Type
journal article