13C high-resolution NMR spectra of cyclic paraffins (C24H48, C28H6e, C32Hg4, C36H72, C^Hgo, C48H96, C64H128, and CggH^), «-paraffins (n-CigH^, «-€22646, and n-C32He6), and a crystalline polyethylene were measured in the solid state. It was shown that the 13C NMR resonance lines of the folded structure region and the trans zigzag structure region in the cyclic paraffins C40H80, C48Hgg, C64H128, and C8oH160 are chemically shifted from one another and that the chemical shifts of «-paraffins with an all-trans zigzag form in the solid state parallel those of the trans zigzag structure region in cyclic paraffins. Their difference is 4-12 ppm. These results demonstrate that cyclic paraffins assume a crystalline conformation with the shape of two parallel straight chains bridged at both ends, producing a freezing of molecular motion. Similarly, it is shown that the 13C NMR signals of the crystalline component and the other component (folded structure or noncrystalline structure) in a dilute-solution-grown crystalline polyethylene are chemically shifted from one another. In this case the latter peak appears as a high-field shoulder on the signal due to the crystalline form. Their difference is about 2.3 ppm. These results are compared with those in cyclic paraffins, and the fold structure is discussed.
High-resolution l 3 C NMR spectra of cyclic paraffins, n-paraffins and polyethylene were measured in 1,2,4trichlorobenzene solution, and the results were compared with the solid state 13C high resolution NMR data measured previously. It is proposed that in cyclic paraffins up to C&, the conformation in the solid state is retained even in solution, all the methylene carbons within the cyclic paraffin exhibiting identical gauche-trans population with fast transition between the conformers in the ring plane, whereas in cyclic paraffins of larger carbon number, the conformation in the solid state is not retained in solution, the gauche-trans populations being different in this case. The conformation of n-paraffins and polyethylene is also discussed.
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