CRYSTALLOGRAPHIC, AM1 AND PM3 SCF-MO INVESTIGATION OF STRONG OH-CENTER-DOT-CENTER-DOT-CENTER-DOT-PI-ALKENE AND ALKYNE HYDROGEN-BONDING INTERACTIONS

A search of the Cambridge structural database reveals eleven alkenes and two alkynes in which particularly short OH ... pi-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 pi-facial bonding may be associated with anomalous reported reactivity. Semiempirical AM1 and PM3 SCF-MO calculations tend to overestimate the C ... H distances in these structures, and very probably underestimate the energies of OH ... pi interaction.