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 sys tem comprising 256 water molecules and four ethane molecules at 279, 2 99, 313, 317, 322, 332 and 346 K. Radial distribution functions for th e water-water and ethane-water pairs reveal a structuring of the first hydration shell of ethane, while the radial distribution functions fo r the ethane-ethane pair show a tendency for ethane particles to aggre gate with increasing temperature in a small temperature range, with a maximum around 317 K. This behavior is consistent with an entropy-driv en hydrophobic attraction between the nonpolar solutes near room tempe rature.