Living anionic stereospecific polymerization of 2‐vinylpyridine, 3. Structure of models of active centres and mechanism of polymerization

Abstract

AbstractThe mechanism of the stereospecific polymerization of 2‐vinylpyridine initiated by organomagnesium compounds in non‐polar solvents, was studied. Triad and pentad data were found to be consistent with a first‐order Markov‐polymerization process. 1H and 13C NMR studies on model molecules of the active species showed an sp3 hybridization of the carbanion and a coordination of the Mg cation by the last and the penultimate pyridine rings of the living chain. The NMR characterization of the monomer coordination with the Mg cation of the active species indicates that two transition states are possible. For steric reasons, only one of them is highly probable, leading to isotactic linkages.