A crystallographic AM1 and PM3 SCF-MO investigation of strong OH ⋯π-alkene and alkyne hydrogen bonding interactions

Abstract

A search of the Cambridge structural database reveals eleven alkenes and two alkynes in which particularly short OH ⋯π-facial hydrogen bonding occurs, a feature largely unrecognised in the original reports of these structures. A wide structural diversity is found for these structures, and in two cases, the π-facial bonding may be associated with anomalous reported reactivity. Semi-empirical AM1 and PM3 SCF-MO calculations tend to overestimate the C ⋯ H distances in these structures, and very probably underestimate the energies of OH ⋯π interaction.