1971 Volume 44 Issue 3 Pages 611-616
The MO calculation of the transannular interaction of eight-membered model systems, containing S,O,N, or C atoms in the position opposed to the C atom of the C=O group, are made by the extended Hückel method and the semi-empirical ASMO SCF method. The relation between the bond order (Prs value or EAB value) and the infrared absorption frequency, νC=O, is discussed. The electronic absorption maxima in the 221 mμ–235 mμ region are assigned to π–π* type transitions of intramolecular charge transfer from the interacting atom, X, to the C=O group. The absorptions in the region from 217 mμ to about 190 mμ are n–σ* type transitions. In the model calculation of the NH3 and HCHO system, it is shown that the interaction is large, the lone pair being directed to the C atom.
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