Hydrogen bonds and conformations in ethylene glycol under pressure.

Ethylene glycol (EG) is a model system for studying complex hydrogen bonding networks in biological compounds such as polysaccharides and sugars. Using in situ high-pressure Raman and infrared absorption spectroscopy, we have investigated the pressure induced variation in the conformations and hydrogen bonding interactions in this compound up to 10 GPa. The high-pressure behavior of Raman modes suggests that EG exists as a liquid with a mixture of trans and gauche conformations up to 3.1 GPa. At ∼4 GPa, a liquid-solid transition is evidenced by the appearance of external Raman modes as well as visual observation. Raman and infrared spectra of EG at high pressures indicate that new hydrogen bonding networks are formed prior to liquid-solid transition and the high pressure phase is stabilized to gauche conformation at pressures above 5 GPa.