Further evidence for a temperature-dependent hydrophobic interaction: the aggregation of ethane in aqueous solutions

A series of molecular dynamics simulations has been performed on a system comprising 256 water molecules and four ethane molecules at 279, 299, 313, 317, 322, 332 and 346 K. Radial distribution functions for the water-water and ethane-water pairs reveal a structuring of the first hydration shell of ethane, while the radial distribution functions for the ethane-ethane pair show a tendency for ethane particles to aggregate with increasing temperature in a small temperature range, with a maximum around 317 K. This behavior is consistent with an emtropy-driven hydrophobic attraction between the nonpolar solutes near room temperature.