Structural and Thermal Studies on Racemic BaC4H4O6•H2O

Abstract

Single crystals of racemic barium tartrate monohydrate, BaC4H4O6·H2O, were grown at 308 K by a gel method using silica gel as the growth medium. Differential scanning calorimetry, thermogravimetric-differential thermal analysis, and X-ray diffraction measurements were performed on the single crystals. The space group symmetry (monoclinic P21/c) and structural parameters were determined at room temperature. The crystal structure consisted of BaO9 and BaO10 polyhedra, two independent C4H4O6 molecules, and O–H···O and C–H···O hydrogen bonds between adjacent H2O or C4H4O6 molecules. Weight losses due to thermal decomposition of racemic BaC4H4O6·H2O were found to occur in the temperature range of 300–1550 K. We suggested that the weight losses were caused by the evaporation of bound water molecules and the evolution of H2CO, H2, CO, and O2 gases from the two C4H4O6 molecules, and that the residual chalky white and black substances that remained as a mixture in the vessel after decomposition were barium oxide (BaO) and barium monocarbide (BaC), respectively.