Reiss Céleste A, Mechelen Jan B van, Goubitz Kees, Peschar René
PANalytical B.V., Lelyweg 1, 7602EA Almelo, The Netherlands.
De Geerkamp 1164, 6545HG Nijmegen, The Netherlands.
Acta Crystallogr C Struct Chem. 2018 Mar 1;74(Pt 3):392-399. doi: 10.1107/S2053229618002619. Epub 2018 Feb 28.
Paracetamol [N-(4-hydroxyphenyl)acetamide, CHNO] has several polymorphs, just like many other drugs. The most stable polymorphs, denoted Forms I and II, can be obtained easily and their crystal structures are known. Crystals of the orthorhombic, less stable, room-temperature Form III are difficult to grow; they need a special recipe to crystallize and suffer from severe preferred orientation. A crystal structure model of Form III has been proposed and solved from a combination of structure prediction and powder X-ray diffraction (PXRD) [Perrin et al. (2009). Chem. Commun. 22, 3181-3183]. The final R value of 0.138 and the corresponding considerable residual trace were reasons to check its validity. A new structure determination of Form III using new high-resolution PXRD data led to a final R value of 0.042 and an improvement of the earlier proposed model. In addition, a reversible phase transition was found at 170-220 K between the orthorhombic Form III and a novel monoclinic Form III-m. The crystal structure of Form III-m has been determined and refined from PXRD data to a final R value of 0.059.
对乙酰氨基酚[N-(4-羟基苯基)乙酰胺，CHNO]与许多其他药物一样，有几种多晶型物。最稳定的多晶型物，即I型和II型，可以很容易地获得，并且它们的晶体结构是已知的。正交晶系、稳定性较差的室温III型晶体很难生长；它们需要特殊的结晶方法，并且存在严重的择优取向问题。已经通过结构预测和粉末X射线衍射（PXRD）相结合的方法提出并解析了III型的晶体结构模型[佩兰等人（2009年）。《化学通讯》22，3181 - 3183]。最终R值为0.138以及相应的可观残余痕迹是检验其有效性的原因。使用新的高分辨率PXRD数据对III型进行新的结构测定，得到的最终R值为0.042，并且对早期提出的模型有所改进。此外，在170 - 220 K之间发现了正交晶系III型与新型单斜晶系III - m型之间的可逆相变。已经根据PXRD数据测定并精修了III - m型的晶体结构，最终R值为0.059。
