Calorimetric and spectroscopic studies of LiSCN solutions in aprotic solvents

Abstract

Using a calorimetric method, enthalpies of solution of lithium thiocyanate in five weakly polar aprotic solvents [HMPA, DMSO, DMF, propylene carbonate (PC) and acetonitrile (MeCN)] have been determined. IR spectroscopy in the range 2000–2100 cm^–1 was applied to the determination of equilibrium constants and enthalpies of ionic lithium thiocyanate association in PC and MeCN. The standard enthalpies of solution (ΔH^°_s) in the highly ionizing solvents, HMPA and DMSO, were obtained by the Criss and Cobble method. Connection of the spectroscopic and calorimetric data also enabled the calculation of ΔH^°_s in the other three solvents where ion pairing occurs to a large extent. The standard enthalpy of solution of LiSCN depends mainly on the basicity of the solvent.