Crystalline ethane-1,2-diol does not have intra-molecular hydrogen bonding: experimental and theoretical charge density studies

Abstract

The X-ray structure and electron density distribution of ethane-1,2-diol (ethylene glycol), obtained at a resolution extending to 1.00 Å^-1 in sin θ/λ (data completion = 100% at 100 K) by in situ cryocrystallization technique is reported. The diol is in the gauche (g'Gt) conformation with the crystal structure stabilised by a network of inter-molecular hydrogen bonds. In addition to the well-recognized O-H···O hydrogen bonds there is topological evidence for C-H···O inter-molecular interactions. There is no experimental electron density based topological evidence for the occurrence of an intra-molecular hydrogen bond. The O···H spacing is ~0.45 Å greater than in the gas-phase with an O-H···O angle close to 90°, calling into question the general assumption that the gauche conformation of ethane-1,2-diol is stabilised by the intra-molecular oxygen-hydrogen interaction.