Conformational analysis of poly(tetrahydrofurandiyls)

The stereoisomeric configurations of poly(2,5-tetraliydrofurandiyl), 1, and poly(2,3-tetrahydrofurandiyl), 2, have been investigated by conformational analysis. Similar results were obtained for 1 and 2, Threodiisotactic (tit) and erythrodisyndiotactic (est) configurations could form low energy helical conformations, whereas erythrodiisotactic (eit) and threodisyndiotactic (tst) configurations generally formed low energy linear conformations. Helical conformations of I placed oxygen atoms at the interior of the helices, but helical conformations of 2 placed oxygen atoms more toward the periphery. The results of ion-binding experiments are interpreted in terms of the results of conformational analysis. Ion-binding experiments are consistent with the suggestion that configurations that can form low energy, helical conformations with oxygen atoms at the interior of the helices could bind cations efficiently. Configurations that can form only low energy linear conformations, or that form helices with oxygen atoms toward the periphery of the helices, should be inefficient in binding cations.