Effect of temperature on the dilution enthalpies of carboxylic acids in aqueous solutions

Dilution enthalpies of propionic, butyric, valeric and caproic acid in water were measured at 293.15, 298.15,303.15 and 308.15 K using an LKB flow microcalorimeter. Experimental data were treated according to the McMillan-Mayer theory to obtain the homotactic enthalpic interaction coefficients. The value of the coefficients is positive and increases with chain length showing that hydrophobic interactions are enhanced. The obtained values of the interaction coefficients are interpreted in terms of solute-solvent and solute-solute interactions and are used as indicative of hydrophobic behavior of the carboxylic acids studied. (C) 2008 Elsevier B.V. All rights reserved.