Relation between van der Waals and Partial Molal Volumes of Organic Molecules in Water

Abstract

The partial molal volumes [Formula: see text] of nonpolar organic molecules (i.e. those having more than three aliphatic carbon atoms per polar hydroxyl, ether, amine, amide, or urea group) in water at 25 °C are given by their van der Waals volumes υw plus the additional empty volume provided by an enclosing shell 0.53 Å thick. An equation relates [Formula: see text] to υw More polar compounds (i.e. those having fewer than two or three aliphatic carbon atoms per polar group) have [Formula: see text] smaller than calculated by the equation; the shrinkage in [Formula: see text] from that computed is linearly related to the fraction of the total surface area of the molecule occupied by the polar group.