Thermochemical Study of [Ce(Hsal)2·(tch)]·2H2O

Abstract

The reaction of cerium chloride heptahydrate with salicylic acid and thioproline produced [Ce(Hsal)2·(tch)]·2H2O [Hsal = salicylate (C7H5O3−), tch = thioprolinate (C4H6NO2S−))], which was isolated and characterized by IR, elemental, chemical, and thermogravimetric analysis. The standard molar enthalpies of solution of [CeCl3·7H2O(s)], [2C7H6O3(s)], [C4H7NO2S(s)], and [Ce(Hsal)2·(tch)·2H2O(s)] in a mixed solvent of absolute ethyl alcohol, dimethyl sulfoxide (DMSO), and 3 mol·L−1 HCl were determined by calorimetry to be ΔsHmΘ[CeCl3·7H2O(s), 298.15 K] = −(42.22 ± 0.37) kJ·mol−1, ΔsHmΘ[2C7H6O3(s), 298.15 K] = (45.54 ± 0.37) kJ·mol−1, ΔsHmΘ[C4H7NSO2(s), 298.15 K] = (21.91 ± 0.60) kJ·mol−1, and ΔsHmΘ[Ce(Hsal)2·(tch)·2H2O(s), 298.15 K] = −(30.87 ± 0.39) kJ·mol−1. The enthalpy change of the reaction CeCl3·7H2O(s) + 2C7H6O3(s) + C4H7NO2S(s) = [Ce(Hsal)2·(tch)]·2H2O(s) + 3HCl(g) + 5H2O(l) was determined to be ΔrHmΘ = (263.12 ± 0.95) kJ·mol−1. From data in the literature, through Hess’s law, the standard molar enthalpy of formation of [Ce(Hsal)2·(tch)]·2H2O(s) was estimated to be ΔfHmΘ[Ce(Hsal)2·(tch)·2H2O(s), 298.15 K] = −(2785.7 ± 3.2) kJ·mol−1.