SynopsisThe NMR spectra of three stereoisomers of 2,4,&trichloroheptane 3s model compounds of poly(viny1 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 a t 60 McJsec. 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(viny1 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 conformatiorrs of the models were determined.