The hydrophobic effect. 1. A consequence of the mobile order in H-bonded liquids

Abstract

The hydrophobic effect has an entropic nature that cannot be explained by classical multicomponent treatments that do not explicitly take into account both the mobility and the nonergodicity of the H-bonds in amphiphilic liquids. The nonergodic thermodynamics of mobile order in H-bonded liquids based on time fractions rather than on concentrations provides a novel qualitative and quantitative explanation for the molecular origin of the hydrophobic effect. Chiefly, this effect corresponds to the loss of the mobile order entropy of associated molecules by dilution with foreign substances. Not being a unique property of water, the propensity of an amphiphilic solvent to induce a solvophobic effect increases primarily as its structuration factor increases, and secondarity as the solute/solvent molar volume ratio increases. On this basis, it can be expected that in the absence of strong solute-solvent specific interactions, the solubility of nonelectrolytes will generally decrease in the following order: butanol > propanol > ethanol > methanol > propylene glycol > ethylene glycol > formamide > water.