Prediction of the Krichevskii parameter for volatile nonelectrolytes in water

Abstract

The Krichevskii parameter, A Kr, for aqueous solutes can be determined from variations of the vapor–liquid distribution constants for a solute at temperatures that are 100–150 K below the critical temperature of water. Pragmatically this means that if one can reliably evaluate the vapor–liquid distribution constant for a solute in water at temperatures up to 500–550 K, then the value of A Kr for this solute can be calculated. This is exactly the approach taken in this study. We use a virial equation of state truncated at the second virial coefficient to evaluate the fugacity coefficients of the solute in the vapor phase and a simple empirical method of thermodynamic integration to calculate Henry’s constant of the solute in water up to 550 K. These results allow prediction of the vapor–liquid distribution constants and the Krichevskii parameter for many volatile nonelectrolytes in water. It appears that the accuracy of predictions is limited mainly by the accuracy of the values of the thermodynamic functions of hydration of solutes at 298.15 K. The values of A Kr for aqueous organic solutes follow group additivity systematics, and we derive a set of corresponding group contribution values for a large number of functional groups.