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本文利用冠醚作为催化剂进行了无溶剂条件下卤代烷烃与卤化钠的卤素交换反应。示踪元素为~(125)I、~(82)Br。考察了不同冠醚(12C4,15C5,18C6和24C8)的催化效率与络合物稳定化能的定量关系。根据晶体测定资料和AIC模型推算的分子几何学结果,计算了这些络合物的离子-偶极作用能量,所得次序与实验结果完全吻合。初步确认这些络合物中的配位键主要来自静电作用的贡献。离子与冠醚环的相对大小(孔径效应)不是决定络合物稳定性的唯一重要的因素;溶剂效应与络合比效应均有较大的贡献。本文列出了锂、钠和钾三种金属离子与12C4、15C5、18C6和24C8形成的络合物稳定化能,较好地解释了本文和国毓智等人发表的实验结果。
In this paper, the halogen exchange reaction of alkyl halides with sodium halide under solvent-free conditions was carried out using crown ether as a catalyst. The trace elements are ~ (125) I, ~ (82) Br. The quantitative relationship between the catalytic efficiency of different crown ethers (12C4, 15C5, 18C6 and 24C8) and the stabilizing energy of complex was investigated. The ion-dipole energies of these complexes were calculated according to the crystal geometry and the molecular geometric results deduced from the AIC model. The obtained order exactly matches the experimental results. The preliminary confirmation of the coordination bond in these complexes mainly comes from the electrostatic contribution. The relative size of the ion and crown ether rings (pore size effect) is not the only factor that determines the stability of the complex; both the solvent effect and the complex ratio effect contribute more. In this paper, the stabilization energies of complexes of lithium, sodium and potassium with 12C4, 15C5, 18C6 and 24C8 are listed, which can well explain the experimental results published in this paper and Guo Yu et al.