苯甲酸晶体中分子结构的研究

In Benzoic Acid Crystal Molecular Structure Research

用压片法测定了苯甲酸晶体的红外光谱,并与苯甲酸的标准红外光谱比较,确证了苯甲酸的红外光谱.用密度泛函B3LYP方法在6-311G**基组水平上对苯甲酸分子的几何结构和红外光谱进行了优化和计算,并将计算所得的苯甲酸各构象的红外频率与其实测的红外光谱进行比较,确定了在晶体中苯甲酸的分子结构,同时在计算中给出了各种频率所对应的红外强度,对光谱进行了归属.通过对光谱归属结果的分析,确定了在晶体中苯甲酸分子是以构象a的分子构象为单体,按图3的形式形成二聚体而存在的.

Examined infrared spectrum of benzoic acid crystal with pressed - disk technique, and compared it with standard infrared spectrum of benzoic acid, as a result, verified the infrared spectrum of benzoic acid. Optimized and calculated geometric structure and infrared spectrum of benzoic acid molecule with density functional B3LYP method on 6 - 311 G^＊＊ base cluster level, and compared the calculated infrared frequency of each conformation of benzoic acid with actually - measured infrared spectrum, thus determined molecular structure of benzoic acid in its crystal form. At the same time, produced the infrared intensity corresponding to each kind of frequency, therefore categorized the infrared spectrum. By analyzing the spectrum category, confirmed that benzoic acid molecule exists in the form of dimer, from monomer＇ with molecular structure demonstrated on graph 3, in its crystal form. in overlapped conformation Ⅰ, a process as