Simple model for nonassociative organic liquids and water

A simple model that has been derived from molecular-level considerations (J . Phys. Chem. B 1998, 102, 5715) is revisited and extended. It is shown tha t it gives a unified and adequate description of a variety of properties re lated to intermolecular interactions, including boiling point, enthalpy of vaporization, vapor pressure, surface tension, and a number of partition an d solubility data for organic liquids that do not contain associative or st rongly polar substituents. All corresponding equations were derived from th e same free energy expression that forms the basis of the model. For the or ganic liquids considered here that include haloalkanes, aromatics, haloarom atics, eaters, and ketones, molecular size as the sole descriptor (characte rized here by molecular volume) can account for 80-90% of the variance. Fur thermore, water, which is a highly abnormal liquid, seems to be integrable within the model by a simple modification of the interaction-related consta nt. This modification is consistent with the modified hydration-shell hydro gen-bond model of Muller, with data on partition and solubility in water, a nd with the large surface tension value of water. Within this approach, the controversy related to different macroscopic/microscopic free energies of interactions per surface area that was raised by Tanford and has recently r esurfaced in the work of Honig, Sharp, and co-workers is also avoided.