Thermochemical Properties of the Dissolution of Rubidium D-Gluconate Rb[D-C6H11O7](2)(s) in Aqueous Solutions

摘要

A novel coordination compound rubidium d-gluconate Rb[d-C6H11O7](s) has been synthesized and characterized by chemical analysis, elemental analysis, and X-ray diffraction. Single-crystal X-ray analysis reveals that the crystal is monoclinic with space group P2(1) and Z = 2. Also, the d-gluconate anion in Rb[d-C6H11O7](s) has a bent-chain conformation, in which the carbon atoms of the anion form two approximate planes. The compound exhibits an obvious chelation of the d-gluconate anions to the rubidum(I) cation and the cation is seven-coordinated to all seven oxygen atoms. The lattice potential energy and ionic volume of the anion d- were obtained to be U (POT) = 484.23 kJ center dot mol(-1) and V (-) = 0.2004 nm(3) from crystallographic data. Molar enthalpies of dissolution of Rb[d-C6H11O7](s) in double-distilled water at various molalities were measured by use of an isoperibol solution-reaction calorimeter at T = 298.15 K. According to Pitzer's electrolyte solution model, the molar enthalpy of dissolution of the title compound at infinite dilution was determined to be . The values of the apparent relative molar enthalpies () of the title compound and relative partial molar enthalpies ( and ) of the solute and the solvent at different concentrations were derived from the experimental enthalpies of dissolution of the compound. Furthermore, the molar enthalpy of hydration of the anion d- was calculated to be Delta H (-) = - (166.4 +/- 2.7) kJ center dot mol(-1) by use of a thermochemical cycle.