1,2-1,4 regioselectivity in the anionic polymerization of dienes. The structure of butadiene-toluene telomers

The structure of lower telomers produced by the sodium-initiated polymeriza tion of butadiene in toluene, when the reaction of chain transfer to the so lvent was pronounced, was studied by H-1 and C-13 NMR spectroscopy. It was shown that the terminal butadiene units of the telomers, which result from abstraction of a proton from the solvent, have an entire 1,4-structure in c ontrast to a predominantly 1,2-structure of the internal units. The experim ental evidence indicates that the structure of the monomer units in the res ulting polymer is not determined by the configuration of the growing chain end but depends on the transition state of the corresponding elementary act .