Xu Mingcan, Harris Kenneth D M
J Phys Chem B. 2007 Aug 2;111(30):8705-7. doi: 10.1021/jp074375j. Epub 2007 Jul 12.
We report a case in which two different crystallization mechanisms occurring in the same crystallization experiment are found to yield different polymorphic outcomes. In particular, we focus on crystallization of glycine from neutral aqueous solution. Crystallization in the bulk solution gives only the metastable alpha-polymorph, as observed in previous studies, whereas crystallization by evaporation of a thin film of the solution on the walls of the crystallization vessel is found to give rise to the thermodynamically stable gamma-polymorph, and furthermore produces an uncharacteristic crystal morphology for this polymorph. A detailed set of control experiments are described that elucidate mechanistic details relating to the latter crystallization process. The fact that crystallization on the walls of a crystallization vessel can yield a different polymorphic outcome from crystallization in the bulk solution in the same experiment has potentially much wider significance with regard to other polymorphic systems.
我们报告了一个案例，发现在同一结晶实验中发生的两种不同结晶机制会产生不同的多晶型结果。具体而言，我们聚焦于甘氨酸从中性水溶液中的结晶。如先前研究中所观察到的，本体溶液中的结晶仅产生亚稳的α-多晶型，而通过在结晶容器壁上蒸发溶液薄膜进行的结晶则产生热力学稳定的γ-多晶型，并且还产生了该多晶型不寻常的晶体形态。描述了一组详细的对照实验，阐明了与后一种结晶过程相关的机理细节。在同一实验中，结晶容器壁上的结晶能产生与本体溶液结晶不同的多晶型结果，这一事实对于其他多晶型系统可能具有更广泛的意义。
