Influence of Tacticity on Some Reactions of PVC

The influence of the tacticity on PVC reactivity is discussed on the basis of preliminary results obtained in ionic dehydrohalo, genation and chlorination reactions. From the reaction of an atactic PVC and a 70% syndiotactic PVC with LiCl in dimethyl-formamide and hexamethylphosphortriamide as solvents, it follows that both the reaction rate and the polyene sequence distribution depend markedly on the syndiotacticity content. This effect is accounted for by the fact that the isotactic parts are preferred in dimethylformamide and the syndiotactic ones in hexamethylphosphoramide. On the other hand, the chlorination of PVC appears to be easier through the heterotactic parts than through the syndiotactic sequences as shown by ¹³C-NMR.