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Investigation of the solid-state polymorphic transformations of piracetam

机译：吡乙酰胺的固态多态转化研究

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摘要

The solid-state polymorphic transformations of 2-oxo-1-pyrrolidine acetamide (piracetam) were investigated using a combination of off-line and online techniques: differential scanning calorimetry (DSC), high temperature X-ray diffraction (HT-XRD), thermal analysis, and hot-stage optical microscopy. Form II and Form III were each observed to transform directly to Form I upon heating, with Form II transforming at a slightly lower temperature. The transformation of both polymorphs to Form I was observed to cause physical cracking of the crystals as well as changing the optical properties. Form I consistently transformed to Form II when cooled. The molecular rearrangements required for the transformation from Form I to Form II were found to be more energetically favorable than those required for the transformation to Form III. The transformation from the metastable Form II to the stable Form III was not observed in the solid-state, while the Form II-Form III transition temperature was found to be higher than the transition temperature of both polymorphs to Form I.
机译：使用离线和在线技术相结合，研究了2-氧代-1-吡咯烷乙酰胺（吡乙酰胺）的固态多态转化：差示扫描量热法（DSC），高温X射线衍射（HT-XRD），热分析和热台光学显微镜。观察到形式II和形式III各自在加热时直接转化为形式I，其中形式II在稍低的温度下转化。观察到两种多晶型物都转变为晶型I，引起晶体的物理开裂以及光学性质的改变。冷却时，形式I始终转变为形式II。发现从形式I到形式II的转化所需的分子重排比向形式III的转化所需的分子重排在能量上更有利。在固态中未观察到从亚稳态晶型II到稳定晶型III的转变，而发现晶型II-晶型III的转变温度高于两种多晶型物向晶型I的转变温度。

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