Catalytic Effect of Solvent Vapors on the Spontaneous Formation of Caffeine–Malonic Acid Cocrystal
Catalytic Effect of Solvent Vapors on the Spontaneous Formation of Caffeine–Malonic Acid Cocrystal
复制标题
溶剂蒸气对咖啡因-丙二酸共晶自发形成的催化作用
DOI：
--
复制
发表时间：
2017
期刊：
影响因子：
--
通讯作者：
M. Mehta
中科院分区：
文献类型：
--
作者：
Canran Ji;Mikaila C. Hoffman;M. Mehta
咖啡因(一种模拟药物)和丙二酸(一种常见的赋形剂伙伴)在常温下混合粉末后，在大约一周的时间内自发形成分子共晶体。我们报告了当粉末混合物暴露在常见实验室溶剂的蒸气中时，该反应的显著催化加速。丙酮和甲醇蒸气的速率提高了1000倍以上，在不到5分钟的时间内实现了定量转化。用粉末X-射线衍射仪对反应过程进行了非原位跟踪，用13C固体核磁共振对产物进行了确证。我们的数据显示没有证据表明存在中间阶段。重量实验表明，溶剂蒸气吸收不是化学计量的，而且是可逆的。这一罕见的气相催化超分子转化的例子对于更深层次地理解扩散控制的固-固反应具有重要的意义。
Caffeine (a model pharmaceutical mimic) and malonic acid (a common excipient partner) are known to form a molecular cocrystal spontaneously over about 1 week when their powders are mixed at ambient conditions. We report the dramatic catalytic acceleration of this reaction when the mixture of powders is exposed to vapors of common laboratory solvents. Acetone and methanol vapors show rate enhancements over 1000-fold, effecting quantitative conversion in less than 5 min. The reaction progress was tracked ex situ by powder X-ray diffraction, and products were verified by 13C solid-state NMR. Our data show no evidence of an intermediate phase. Gravimetric experiments show that solvent vapor uptake is not stoichiometric and is reversible. This rare example of gas phase catalysis of supramolecular transformations has important implications for a deeper mechanistic understanding of diffusion-controlled solid–solid reactions.