An odd-even effect on solubility of dicarboxylic acids in organic solvents

The solubility of the homologous series of dicarboxylic acids, HOOC-(CH2)(n) (2)-COOH (n = 2 to 10), in ethanol, acetic acid, acetone and ethyl acetate was measured at temperatures ranging from (278.15 to 323.15) K by a static analytic method at atmospheric pressure. Dicarboxylic acids with even number of carbon atoms exhibit lower values of solubility than adjacent homologues with odd carbon numbers. This odd-even effect of solubility is attributed to the twist of molecules and interlayer packing in solid state as explained in our previous work. The alternation varies in different solvents, which is believed to be associated with the properties of solvents. Finally, the dissolution enthalpy, dissolution entropy and the molar Gibbs free energy were calculated using the fitting parameters of the modified Apelblat equation. The molar Gibbs free energy also showed apparent odd-even alternation in keeping with the alternation of solubility. (C) 2014 Elsevier Ltd. All rights reserved.