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An INDO-LMO and 13C NMR spectroscopic study of the CH bonds in tetracyclo[3.2.0.02,7.04,6]heptane (quadricyclane) and tricyclo[3.1.0.02,4]hexane

par Figeys, Hubert ;Geerlings, Pau̧l;Raeymaekers, Paul ;Van Lommen, Guy;Defay, Nicole
Référence Tetrahedron, 31, 15, page (1731-1735)
Publication Publié, 1975

Article révisé par les pairs

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Résumé :

Using an INDO approximation to Von Niessen's charge density localization method, the percent s character of the C atom hybrid orbitals engaged in CH bonds is computed for a series of open-chain and cyclic saturated and unsaturated hydrocarbons. A semi-empirical linear relationship is found between these quantities and the experimental nuclear spin-spin coupling constants JCH (standard deviation 4·98 Hz). The experimental values of JCH were measured for quadricyclane (1) and tricyclo[3.1.0.02,4]hexane (2) and were shown to be in fair agreement with the theoretical predictions. An analogous relationship is also established between the percent s character of the involved C atom hybrid orbital and the CH bond distance, the standard deviation being 0·0040 Å. This relation is used in order to predict the different CH bond lengths in the vibrational ground state of 1 and 2, for which equal CH distances were assumed in the analysis of electron diffraction experiments. The results indicate that molecular geometries can be refined with the use of semi-empirical correlations of the above mentioned type. © 1975.