There is a considerable disagreement about the range to which solutes perturb water structure. The dominant view is that bulk behavior is attained within one or two hydration shells from the solute. However, the extrapolation of thermodynamic and kinetic data as well as long-standing continuum-solvent models suggest that the perturbation is much longer-ranged. Here we analyse the hydrogen-bond structure of water around halide anions, alkali cations, and noble-gas solutes using molecular dynamics simulations (S. J. Irudayam, R. H. Henchman, J. Chem. Phys., 2012, 137, 034508). We observe perturbations in the numbers of water's hydrogen bonds in the entire simulation box, less so at longer range, but never the same as bulk.  This effect is independent of solute-size, hydrogen-bond definition or box size. It manifests itself as an excess of acceptors around halide anions, an excess of donors around alkali cations, and weakly enhanced tetrahedrality and an oscillating excess and deficiency of single and triple acceptors around noble-gas solutes. The structuring in hydrogen bonds induced by the solute appears to be compensated by a cancelling perturbation spread over as many water molecules as possible.

Long-range hydrogen-bond structure in aqueous solutions

245th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.