Synthesis and standard enthalpy of formation of magnesium L-threonate

Abstract

The white powder of magnesium L-threonate was obtained by extracting with alcohol the concentrated solution obtained from the reaction between L-threonic acid solution prepared by double decomposition reaction of calcium L-threonate with oxalic acid and superfluous magnesium oxide at 80°C. The composition of the new compound was determined by chemical and elemental analyses and its formula fits Mg(C4H7O5)2·H 2O, the IR spectra indicated that Mg2+ in the compound coordinates to oxygen atom of the carboxyl group, while the proton of the carboxyl group is dissociated, it was assumed that the coordination number of Mg2+ was 4. The results of TG-DTG showed that the compound had fairish stability, the intermediate and final product of the thermal decomposition of the compound are Mg(C4H7O5)2, Mg(CH3COO)2 and MgO, respectively. The constant volume combustion energy of the compound, ΔcE, was determined as (-10 407.34±4.67) kJ·mol-1 by a precise rotating-bomb calorimeter at 298.15 K, its standard enthalpies of combustion, ΔcHm⊖, and standard enthalpies of formation, ΔfHm⊖, were calculated as (-3 249.49±1.46) kJ·mol-1 and (-2 786.23±1.84) kJ·mol-1, respectively.