Extracting hydrophobic free energies from (Received 2

ABSTRACT: Solubility and vapor pressure measurements of hydrocarbons in water are general1 thought reassessment of the solubility data on the basis of new developments in solution thermodynamics suggests that the hydrophobic surface free energy for hydrocarbon solutes is 46-47 cal/(mol*A2), although the actual value depends strongly on curvature effects [Nicholls et al. (1991) Proteins (in press); Sharp et al. (1991) Science 252, 106-1091. The arguments to support such a significant increase in the estimate of the hy-drophobic effect stem partly from theoretical considerations and partly from the experimental results of De Young and Dill [(1990) J. Phys. Chem. 94,801-8091 on benzene partition between water and alkane solvents. Previous estimates of the hydrophobic effect derive from an analysis of solute partition data, which does not fully account for changes in volume entropy. We show here how the ideal gas equations, combined with experimental molar volumes, can account for such changes. Revised solubility scales for the 20 amin