Hydrophobicity of benzene

The present work tries to clarify the molecular origin of the poor solubility of benzene in water. The transfer of benzene from pure liquid phase into water is dissected in two processes: transfer from gas phase to pure liquid benzene; and transfer from gas phase to liquid water. The two solvation processes are analyzed in the temperature range 5-100 degrees C according to Lee's Theory. The solvation Gibbs energy change is determined by the balance between the work of cavity creation in the solvent, and the dispersive interactions of the inserted benzene molecule with the surrounding solvent molecules. The purely structural solvent reorganization upon solute insertion proves to be a compensating process. The analysis shows that the work of cavity creation is larger in water than in benzene, whereas the attractive energetic interactions are stronger in benzene than in water; this scenario is true at any temperature. Therefore, both terms act in the same direction, contrasting the transfer of benzene from pure liquid phase into water and determining its hydrophobicity. (C) 1999 Elsevier Science B.V. All rights reserved.