C-13 NMR CHEMICAL-SHIFT ASSIGNMENTS OF POLY(VINYL CHLORIDE) BASED ON THE 2D-INADEQUATE SPECTRUM

Two-dimensional (2D) heteronuclear H-1-C-13, homonuclear H-1, and spin-lock relay NMR experiments have been used to provide C-13 NMR chemical shift assignments of stereosequences in poly(vinyl chloride). However, relative areas of methylene tetrad peaks based on the assignments given by these 2D NMR experiments do not agree with the relative areas predicted by Bernoullian propagation statistics. Since the methods of the 2D experiments are correct, this is a puzzle. In this study, tetrad and pentad assignments are proposed on the basis of the carbon-carbon connectivities revealed by the PD-INADEQUATE (two-dimensional incredible natural abundance double quantum transfer experiment) spectrum. The tetrad assignments given by 2D-INADEQUATE experiments show that there are two mmr peaks and that one of them overlaps the mrm peak. These assignments differ from the previous assignments and resolve the contradication in relative peak areas. The relative areas of methylene peaks based on the assignments from the 2D-INADEQUATE spectrum agree with those predicted by Bernoullian propagation statistics.