NMR spectra of model compounds of poly(vinyl chloride)

The NMR spectra of three stereoisomers of 2,4,6-trichloroheptane as model compounds of poly(vinyl chloride) have been studied. Spectra were observed at 60 and 100 Mc./sec., both at room temperature and at high temperatures. A spin-decoupling experiment was performed. Computational analysis of the spectra was carried out on an IBM 7090 computer. The difference of the chemical shifts of the two meso methylene protons at 60 Mc./sec. was found to be ca. 7 cps. for the isotactic three-unit model while it was ca. 16 cps. for the isotactic two-unit model or heterotactic three-unit model. The spectra of poly(vinyl chloride) were interpreted reasonably on the basis of this result. Observed values of vicinal coupling constants of model compounds were interpreted as the weighted means of those for several conformations, and the stable conformations of the models were determined.