Theoretical studies of unusually short bond lengths in oxirane and derivatives

The pi -Complex-Back-Donation model (pi -cbd) has been used together with t he topological analysis of the ab initio and semiempirical densities to inv estigate bond lengths in the oxirane molecule and derivatives. Both models offer similar conclusions. The shortenings of the C-C bond in the oxirane r ing and of the neighbouring C-C bond arise mainly from the substituent grou ps. However, neither the pi -cbd model nor the atoms in molecules model off ers a satisfactory explanation for the elongation of one of the C-O bonds. (C) 2001 Elsevier Science B.V. All rights reserved.