PENTAD ASSIGNMENTS OF METHINE CARBON RESONANCES IN STEREOREGULAR ETHYLENE PROPYLENE COPOLYMER BASED ON TWO-DIMENSIONAL INADEQUATE NMR-SPECTRUM

It is demonstrated that the 13C double quantum two dimensional (2D-INADEQUATE) NMR spectrum is very useful for 13C NMR chemical shift assignments of split peaks arising from differences in long range sequences. The 2D-INADEQUATE spectrum of streoregular ethylene-propylene copolymer revealed the detailed connectivities between methyl and methine carbons. By tracing these connectivities, the pentad comonomer sequence assignments of methine carbon could be determined for the first time. The 13C chemical shifts of methyl carbons in the different pentad sequences, predicted by the chemical shift calculation via the gamma-effect, were used as references for the assignments of methine carbon resonances.