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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Structural, Kinetic and Thermodynamic Aspects of the Conformational Dimorphism of Diethyl 3,6-Dibromo-2,5-dihydroxyterephthalate
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Structural, Kinetic and Thermodynamic Aspects of the Conformational Dimorphism of Diethyl 3,6-Dibromo-2,5-dihydroxyterephthalate

机译：3,6-二溴-2,5-二羟基对苯二甲酸二乙酯构象二态的结构，动力学和热力学方面

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摘要

The crystal structures of the title compound and of its ethanol solvate have been determined by X-ray diffraction. The compound crystallizes in two different crystal forms (I: Plx, high-temperature stable modification, II: P2Jc, room-temperature stable modification), which differ in molecular conformation and hydrogen bonding. Ab initio calculations show that both observed conformations correspond to local energy minima and predict the conformation in polymorph (II) to be energetically more favourable. Packing energy calculations confirm that form (II) should be more stable than form (I). Crystals of both modifications and a solvate, containing 2 equiv. of ethanol, can be obtained by slow crystallization from ethanolic solution. Modification (II) transforms to (I) at 391K, as shown by optical microscopy, powder diffraction and differential thermal analysis (DTA), whereas (I) melts at 429 K without previous transformation.
机译：通过X射线衍射测定了标题化合物及其乙醇溶剂化物的晶体结构。该化合物以两种不同的晶体形式结晶（I：Plx / n，高温稳定的修饰，II：P2Jc，室温稳定的修饰），它们的分子构象和氢键不同。从头算计算表明，两个观察到的构象均对应于局部能量最小值，并预测多晶型物（II）中的构象在能量上更有利。包装能量的计算证实，形式（II）应该比形式（I）更稳定。改性和溶剂化物的晶体，均含2当量。通过从乙醇溶液中缓慢结晶可以获得乙醇。如光学显微镜，粉末衍射和差热分析（​​DTA）所示，改性（II）在391K时转变为（I），而（I）在429 K时熔化而没有事先转变。

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