Using methods of chemical kinetics and quantum modeling, we investigated the mechanism by which base catalysts affect the regioselectivity of the ring opening of 2‐(chloromethyl)oxirane by benzoic acid. The model reaction was carried out using 2‐(chloromethyl)oxirane as both reagent and solvent at temperatures of 303‐333 K. Rate constants and activation parameters of the ring opening were determined for the overall reaction and for the formation of the isomeric “normal” and “abnormal” products. Density functional theory B3LYP/6‐31+G** was used to examine possible reaction pathways. A comparison of experimental measurements and theoretical calculations confirm that the rate‐limiting step is the attack of the benzoate anion on the C¹ and C² positions of 2‐(chloromethyl)oxirane. The present results indicate that the regioselectivity of the 2‐(chloromethyl)oxirane ring opening by benzoic acid depends on the ratio of A2 mechanisms, S_N2 and “borderline” S_N2 type. This suggests that weak nucleophilic base catalysts can increase the reaction regiospecificity by increasing the contribution of the S_N2 pathway.

中文翻译：

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苯甲酸碱催化2-（氯甲基）环氧乙烷开环机理的实验和计算研究

利用化学动力学和量子建模方法，我们研究了碱催化剂影响苯甲酸对2-（氯甲基）环氧乙烷开环的区域选择性的机理。使用2-（氯甲基）环氧乙烷作为试剂和溶剂，在303-333 K的温度下进行模型反应。确定了整个反应的反应速率常数和开环活化参数，并确定了“正构异构体”和“异常”产品。密度泛函理论B3LYP / 6-31 + G **用于检查可能的反应途径。实验测量值和理论计算值的比较证实，限速步骤是苯甲酸酯阴离子对C ¹和C ²的侵蚀2-（氯甲基）环氧乙烷的位置 目前的结果表明苯甲酸对2-（氯甲基）环氧乙烷开环的区域选择性取决于A 2机理，S _N 2和“边界” S _N 2类型的比率。这表明弱亲核碱催化剂可以通过增加S _N 2途径的贡献来增加反应区域特异性。