Thermodynamic properties of nonpolar solutes in water and the structure of hydrophobic hydration shells

Abstract

Experimental partial molar entropies and heat capacities in water for noble gases, nonpolar diatomic gases, and hydrocarbons were analyzed thermodynamically by delphic dissection to evaluate the contributions from solute-induced perturbations of the water network. These contributions, which are typically large, were then interpreted in terms of the familiar two-state model of liquid water. Changes in the fractions of the two states and of their relative enthalpies, per mole of solute, were thus evaluated. The numbers of water molecules that are nearest neighbors to the solute, and the manner in which the nearest neighbors are tied to the bulk water network, could be elucidated.