L-苏糖酸镁的制备及标准生成焓

以L-苏糖酸钙与草酸的复分解反应得到的L-苏糖酸溶液，在80 ℃下与过量MgO反应较长时间， 滤液浓缩后加无水乙醇制得L-苏糖酸镁白色粉末.用化学分析及元素分析确定其组成为Mg(C4H7O5)2•H2O. IR光谱分析表明,化合物中苏糖酸以羧基氧原子与Mg2＋配位，Mg2＋为sp3杂化态，配位数为4. TD－DTG结果说明，它在热分解中有一定稳定性，而经脱水和生成Mg(OAc)2，最后生成MgO.用转动弹热量计测得其恒容燃烧能ΔE为 (－10407.34±4.67) kJ•mol－1,计算其标准燃烧焓ΔcHm和标准生成焓ΔfHm分别为(－3 249.49±1.46) kJ•mol－1和(－2 786.23±1.84) kJ•mol－1.

Synthesis and Standard Enthalpy of Formation of Magnesium L-Threonate

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 ℃. The composition of the new compound was determined by chemical and elemental analyses and its formula fits Mg(C4H7O5)2•H2O, 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.