Ab initio studies of structural features not easily amenable to experiment: Part III. The influence of lone pair orbital interactions on molecular structure

The characteristic structural asymmetries and distortions of AXYB systems in which an electron lone pair is at Y are discussed on the basis of the completely relaxed ab initio equilibrium geometries of a number of representative systems including various conformations of methanediol, hydrazine, 1,2-dimethylhydrazine and of compounds with CH₃ groups adjacent to OH, OCH₃, NH, NCH₃ and C(π). It is found that, regardless of quantitative overlap and energy gap factors, all calculated trends in the relative extensions of bond distances and bond angles can be correlated in every detail to qualitative predictions based only on the orientational aspects of orbital interaction concepts.