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以差示扫描量热法、热重法、热重-傅里叶红外光谱联用技术对两种环烯醚萜类化合物京尼平和京尼平苷在氮气环境下进行了非等温热分析,采用Van't Hoff方程建立回归曲线求得了它们的纯度和熔点。结合量子化学GAMESS软件分子模拟计算、热失重百分数和热解逸出气体红外光谱分析,对两种化合物化学键的断裂情况进行了理论推断和验证。应用积分Coats-Redfern法和微分Achar法两种热分析动力学方法对热重实验数据进行了分析,推断了各步分解最概然机理函数,并求得了相应的动力学参数-表观活化能E a和指前因子A。研究表明,京尼平和京尼平苷的纯度分别为99.53%和99.29%,其熔点分别为120.85℃和161.53℃;京尼平的热分解从151℃左右开始,共分为两步,而京尼平苷首先在29~110℃发生了失水干燥失重,热分解由213℃开始,至361℃结束,它们的失重百分数、分子模拟推断和逸出气体红外光谱解析三者能够对热分解过程的化学键断裂情况进行判断;京尼平第一步热分解是化学反应控制机制(符合反应级数方程),第二步则为三维扩散控制机制(符合Z.-L.-T.方程),而京尼平苷的热分解是化学反应控制机制(符合反应级数方程);京尼平两步热分解的活化能差别不大,但比京尼平苷的小得多,说明引入糖苷键的京尼平苷变得更为稳定;据京尼平和京尼平苷第一步分解的动力学参数,推断二者在室温(25℃)的贮存期分别为1.5~2年和4~5年。
Two kinds of iridoid genipin genipin and geniposidase were analyzed by differential scanning calorimetry, thermogravimetry and TG-FTIR in a non-isothermal thermal analysis , Using Van't Hoff equation regression curve obtained their purity and melting point. Combined with quantum chemistry calculations of GAMESS software, percentages of thermogravimetry and pyrolysis gas analysis, the fracture states of chemical bonds between the two compounds were theoretically inferred and verified. The thermo-gravimetric experimental data were analyzed by Coats-Redfern method and differential Achar method, and the most probable mechanism function of each step was deduced. The corresponding kinetic parameters-apparent activation energy E a and pre-exponential factor A. The results showed that the purity of genipin and geniposide were 99.53% and 99.29%, respectively. Their melting points were 120.85 ℃ and 161.53 ℃, respectively. The thermal decomposition of genipin began at about 151 ℃ and was divided into two steps. Niph glycosides firstly dehydrated and lost weight at 29-110 ° C, and the thermal decomposition started from 213 ° C to the end of 361 ° C. The percentages of weight loss, molecular simulation and gas evolution by escaped infrared spectroscopy showed that niphonin The first step of genipin thermal decomposition is the chemical reaction control mechanism (in line with the reaction series equation), the second step is the three-dimensional diffusion control mechanism (in line with Z.-L.-T. equation) The thermal decomposition of geniposide is a chemical reaction control mechanism (in line with the reaction series equation); genipin two-step thermal decomposition of the activation energy difference is not significant, but much smaller than the geniposide, indicating the introduction of glycosidic bonds Of geniposidase became more stable. According to the kinetic parameters of the decomposition of genipin and geniposide in the first step, the storage period of both genders at room temperature (25 ° C.) was 1.5 to 2 years and 4 to 5 year.