Ab initio molecular orbital theory has been used to model the structure of perfluoro-n-alkane chains. Ex tended basis set calculations on C2F6, C3F8, and n-C4F 10 show that C2F6 and C3F8 have staggered geometries with D3d and C2v symmetry, respectively. The butane n-C4F10 has a helical C 2 structure that is 0.5 kcal/mol more stable than the C2h structure. Smaller basis set calculations on the larger n-alkanes, n-C 6F14 and n-C8F18, also show he lical structures of C2 symmetry. These results demon strate that the helicity observed in polytetrafluoroethy lene (Teflon®) chains is due to inherent electronic prop erties of the isolated chains and not to crystal packing forces. Structural, energetic, and vibration spectral infor mation on the perfluoro-n-alkanes is presented. This study demonstrates the power of modern theoretical chemistry methods, and how computational approaches can complement experimentation in predicting molecular structure and behavior.
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