Web Release Date: January 17,
Structure of Hydrophobic Hydration of Benzene and Hexafluorobenzene from First Principles
and
Department of Theoretical and Computational Physics, Graz University of Technology, Graz, Austria, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 84559, and University of California, Davis, Davis, California 95616
Received: August 22, 2006
In Final Form: October 29, 2006
Abstract:
We report on the aqueous hydration of benzene and hexafluorobenzene, as obtained by carrying out extensive
(>100 ps) first principles molecular dynamics simulations. Our results show that benzene and hexafluorobenzene do not behave as ordinary hydrophobic solutes, but rather present two distinct regions, one
equatorial and the other axial, that exhibit different solvation properties. While in both cases the equatorial
regions behave as typical hydrophobic solutes, the solvation properties of the axial regions depend
strongly on the nature of the 
-water interaction. In particular, -hydrogen and -lone pair interactions are
found to dominate in benzene and hexafluorobenzene, respectively, which leads to substantially different
orientations of water near the two solutes. We present atomic and electronic structure results (in terms of
Maximally Localized Wannier Functions) providing a microscopic description of benzene- and hexafluorobenzene-water interfaces, as well as a comparative study of the two solutes. Our results point at the
importance of an accurate description of interfacial water to characterize hydration properties of apolar
molecules, as these are strongly influenced by subtle charge rearrangements and dipole moment redistributions
in interfacial regions.
Download the full text: PDF | HTML
