Thermodynamics of Ion Association of s-Acetylthiocholine Halides and Perchlorate in Acetonitrile

Abstract

Thermodynamic parameters (DHº, DGº, DSº) and the activation energy (DEs) were calculated to explain the limiting equivalent conductance (L₀) and ion association constant (K_A) of s-acetylthiocholine halides and perchlorate in acetonitrile at different temperatures by using conductance measurements. It has been evaluated by using Fuoss-Onsager equation. It is evident that the values of (L₀) increase regularly with increase in temperature. For all salts of s-acetylthiocholine, (L₀) indicates less solvation or higher mobility of the ions in all solvent systems studied. The free energy change DGº values are negative for all salts (Br^–, I^– and ClO₄^–). Clearly strengthening to interionic association at higher temperatures is largely caused by a decrease in the permitivity of the solvent. The positive values of (DHº) for three salts (Br^–, I^– and ClO₄^–) show that the association processes are endothermic in nature. Entropy change (DSº) values are positive for all salts indicate the randomness of ions in all solvent systems studied.