Paul Popelier and his team have used quantum chemical topology (QCT) to reveal the dynamics of atom–atom interactions in a liquid.
Liquid mixtures, such as ethanol–water and methanol–water, are useful for research into molecular studies of the hydrophobic effect, which governs biological structures and plays a role in protein folding. Also, in the case of ethanol, its specific use as a bio-fuel creates an interest in understanding its interaction with water.
The team studied the behaviour of water and ethanol molecules in terms of O-H…O, C-H…O and H…H interactions. They found that the water molecule formed one to six C-H…O and one to four O-H…O interactions as a proton acceptor.
Also, the more localised a dynamical bond critical point distribution, the higher the average electron density at its bond critical points. The formation of multiple C-H…O interactions affected the shape of the oxygen basin of the water molecule. They also found that the hydrogen atoms of water strongly preferred to form H…H interactions with ethanol’s alkyl hydrogen atoms over its hydroxyl hydrogen.
Reference:
The dynamic behavior of a liquid ethanol-water mixture: a perspective from Quantum Chemical Topology
Paul L. A. Popelier et al, Phys. Chem. Chem. Phys., 2011, DOI: 10.1039/c0cp02869j
