Hydrophobic interaction and structural changes in the solvent

The effect of structural changes in the solvent (usually water) on the thermodynamics of the hydrophobic interaction process is examined within the framework of classical statistical mechanics. The concept of the “structure of water” is first defined in a precise way, yet reflecting the conventional definition that has been, implicitly and qualitatively, employed by many authors. Using this concept, we proceed to show that structural changes in the solvent, induced by the hydrophobic interaction process, cannot affect the strength of the hydrophobic interaction. On the other hand, the entropy and enthalpy changes, associated with the same process, may well be affected. Some qualitative arguments are presented showing that large structural changes are expected from a complex solvent such as water.