Solutions of organic solutes. Part 3.—Compression and structure

Abstract

Using the chemical thermodynamic (CT) model outlined in part 1 (J. V. Leyendekkers, J. Phys. Chem., 1986, 90, 5449), equations are derived for estimating the effect of pressure on the cavity occupied by an organic solute in solution. The relative effects of pressure on the packing and dynamic spaces for twenty solutes (solids and liquids) are calculated. Various structural factors and work functions for the solute in solution are obtained and these are shown to be correlated with dielectric properties and the cohesive energy density of the pure solute. Such relationships show distinct patterns amongst the solutes and could be useful as guides to classification of solutes. Equations for predicting the change in compressibility with concentration (S_kT) are derived. Agreement is good between experimental and calculated values of S_kT for most of the solutes considered here and also the amino acids covered in part 1.