Long-range σ-inductive interactions through saturated C–C bonds in polymethylene chains

摘要: Analysis of the NMR shifts unsaturated carbon in monounsaturated linear long-chain esters, alcohols and acids, including data from jojoba oil, shows a highly dependence logarithm shift separation CC bond upon number bonds separating this ester moiety. Both linearity dependence, observation that it does not change sign reversal grouping, rule out ‘electric field effect’ as an explanation, but are semi-quantitatively consistent with remarkably simple, ‘σ-inductive’ through-bond mechanism. Semi-empirical MO calculations support conclusion. The attenuation factor is 1.75 per saturated C–C each class compound, although actual separations, for given chain length, vary up to twofold changes polarizing group (Z)–(E) isomerism at bond. Other series compounds show same factor.