Simple lattice model for solvation of nonpolar molecules in hydrogen-bonded liquids

A lattice model is presented that gives closed-form expressions for solvation thermodynamic parameters in hydrogen-bonded solvents including water and alcohols. The model allows one to handle the size of solutes in a very simple way using a single parameter and accounts for the influence of the solute on the entropy of the solvent hydrogen bond network. The model suggests that the influence of solute insertion on the orientational freedom of nearby water molecules is important but not entirely responsible for the unusual entropy of the hydrophobic effect. Appeal to formal exact expressions for solvation thermodynamic parameters shows that the unusual thermodynamic descriptors of hydrophobic solvation can result from an unusual positive covariance between the energy of interaction between a solute and the solvent and the energy of interaction among solvent molecules. These effects are incorporated in the lattice model by ascribing a temperature dependence to the solute-solvent and solvent-solvent-solvent interaction parameters. When suitably parameterized, the model is consistent with the signature features of the hydrophobic effect.