Three-membered rings. Part I. Semiempirical calculations of the molecular conformation of compounds of the type PhCH·X·CH2(X = CH2, O, S, NH, or CCl2)

Publisher Website
Google Scholar
Abstract
Semiempirical CNDO/2 calculations have been performed on the series of compounds phenylcyclopropane, phenyloxiran, phenylthiiran, phenylaziridine, and 1,1-dichloro-2-phenylcyclopropane. From the energies obtained, it is concluded that for all these molecules the most stable conformation is that in which the planes of the phenyl group and of the three-membered ring are orthogonal (or very close to orthogonal) to one another. These results indicate that inter-ring conjugation is present. The energy barrier to rotation about the phenyl–threemembered ring bond is ⩽ 13.4 kJ mol–1 for the first four compounds, which suggests that interconversion between one orthogonal form and another, equivalent to the first, is rapid at room temperature. Instead, 1,1-dichloro-2-phenylcyclopropane, because of the steric and electrostatic effects of the chlorine atoms, gives an energy barrier of 61.9 kJ mol–1. For this reason interconversion in this molecule is slow.

This publication has 0 references indexed in Scilit: