EVIDENCE FOR O-H...C AND N-H...C HYDROGEN-BONDING IN CRYSTALLINE ALKYNES, ALKENES, AND AROMATICS

Attempts have been made to understand the nature and significance of hydrogen bonds of the type X-H...C (X = O,N). These unusual interactions have been discussed recently. Crystallographic studies on 17alpha-ethynylandrosta-2,4-dieno[2,3-d]dihydroxazol-17beta-ol (donazole) provide direct evidence of such an O-H...C interaction. Ab initio computations, IR spectroscopy, and database studies show that these hydrogen bonds, while uncommon, are energetically and structurally significant.