Single crystals of 2-tert-butyl-5-methylphenol anhydrate and 2-tert-butyl-5-methylphenol quarterhydrate were prepared and presented for the first time in this work. The structures were characterized by single-crystal X-ray diffraction and DSC analysis. The solid–liquid equilibrium (SLE) for 2-tert-butyl-4-methylphenol with 2-tert-butyl-5-methylphenol anhydrate or 2-tert-butyl-5-methylphenol quarterhydrate was studied by the cooling–heating recycling method using a synthetic visual technique at atmospheric pressure (101.6 ± 1.2 kPa). The experimental SLE data for the two binary systems were reported, and both systems showed simple eutectic behavior. The SLE data were further correlated by Wilson and NRTL (nonrandom two-liquid) models, and the optimally fitted parameters of the two systems were presented. Computational studies on geometric optimization and energy calculation were performed using density functional theory, and the lower energy configuration of 2-tert-butyl-5-methylphenol quarterhydrate could explain the spontaneous incorporation of water in the anhydrous form. These novel data provide valuable information in designing and optimizing the melt crystallization process of tert-butylmethylphenol isomers.

中文翻译：

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叔丁基甲基苯酚异构体的晶体结构和二元熔融固液平衡

本工作首次制备并展示了2-叔丁基-5-甲基苯酚无水物和2-叔丁基-5-甲基苯酚四水合物的单晶。通过单晶X射线衍射和DSC分析对结构进行了表征。采用冷热循环法研究了2-叔丁基-4-甲基苯酚与2-叔丁基-5-甲基苯酚无水物或2-叔丁基-5-甲基苯酚四水合物的固液平衡（SLE）大气压力 (101.6 ± 1.2 kPa) 下的合成视觉技术。报告了两个二元系统的实验 SLE 数据，两个系统都表现出简单的共晶行为。 SLE数据通过Wilson和NRTL（非随机双液）模型进一步相关，并给出了两个系统的最佳拟合参数。利用密度泛函理论进行几何优化和能量计算的计算研究，2-叔丁基-5-甲基苯酚四水合物的较低能量构型可以解释无水形式水的自发结合。这些新数据为设计和优化叔丁基甲基苯酚异构体的熔融结晶工艺提供了有价值的信息。