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Conformation of Ethylene Glycol in the Liquid State: Intra- versus Intermolecular Interactions
Ethylene glycol is
a typical rotor molecule with the three dihedral angles that allow
for a number of possible conformers. The geometry of the molecule
in the liquid state brings into sharp focus the competition between
intra- and inter-molecular interactions in deciding conformation.
Here, we report a conformational analysis of ethylene glycol in the
liquid state from ab initio molecular dynamics simulations. Our results
highlight the importance of intermolecular hydrogen bonding over intramolecular
interactions in the liquid, with the central OCCO linkage adopting
both gauche and trans geometries in contrast to the gas phase, wherein
only the gauche has been reported. The influence of intermolecular
interactions on the conformation of the terminal CCOH moieties is
even more striking, with certain regions of conformational space,
wherein the ethylene glycol molecule cannot participate with its full
complement of intermolecular hydrogen bonds, excluded. The results
are in agreement with Raman and NMR spectroscopic studies of liquid
ethylene glycol, but at the same time they are able to provide new
insights into how intermolecular interactions favor certain conformations
while excluding others