Structural and Thermal Studies on RacemicBaC4H4O6·H2O

摘要

Single crystals of racemic barium tartrate monohydrate, BaC_(4)H_(4)O_(6)·H_(2)O, 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 P 2_(1)/ c ) and structural parameters were determined at room temperature. The crystal structure consisted of BaO_(9) and BaO_(10) polyhedra, two independent C_(4)H_(4)O_(6) molecules, and O–H···O and C–H···O hydrogen bonds between adjacent H_(2)O or C_(4)H_(4)O_(6) molecules. Weight losses due to thermal decomposition of racemic BaC_(4)H_(4)O_(6)·H_(2)O 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 H_(2)CO, H_(2), CO, and O_(2 )gases from the two C_(4)H_(4)O_(6) 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.