Crystal structure and thermochemical properties of potassium pyruvate C₃H₃O₃K(s)

Abstract

One important compound potassium pyruvate C₃H₃O₃K(s) is synthesized and characterized by chemical analysis, elemental analysis, and X-ray crystallography. X-ray single-crystal structural analysis reveals that the compound is formed by one CH₃COCOO⁻ anion and one metal cation K⁺. An obvious feature of the crystal structure of the compound is the formation of the five-membered chelate ring, and it is good for the stability of the compound in structure. The lattice potential energy of the compound and ionic volume of the anion CH₃COCOO⁻ are obtained from crystallographic data. The lattice potential energy is determined to be: U _POT[C₃H₃O₃K(s)] = 567.7 kJ mol⁻¹. The V ₋ (the volume of the anion CH₃COCOO⁻) is estimated to be 0.088 nm³. Molar enthalpies of dissolution of the compound at various molalities in the double-distilled water are measured by use of an isoperibol solution-reaction calorimeter at 298.15 K. According to Pitzer’s electrolyte solution theory, molar enthalpy of dissolution of C₃H₃O₃K(s) at infinite dilution is derived to be 22.9 kJ mol⁻¹. The values of relative apparent molar enthalpies (^Φ L), relative partial molar enthalpies ($\bar{L}_{2}$) of the compound, and relative partial molar enthalpies ($\bar{L}_{1}$) of the solvent (water) at different concentrations m/(mol kg⁻¹) are derived from the experimental values of the enthalpies of dissolution of the compound. Finally, the molar enthalpy of hydration of the anion CH₃COCOO⁻(g) is calculated to be −227.8 kJ mol⁻¹ by the design of the thermochemical cycle.