卟啉内氢迁移反应氟取代基效应的理论研究  

Theoretical Study on Fluoro Substitution Effect of the Transfer Reaction of Inner Hydrogen Atoms in Porphyrin

作　　者：廖玉婷[1] 饶火瑜[1] 孔凡峰[1] 罗明标[1] 

机构地区：[1]东华理工学院应用化学系,抚州344000

出　　处：《Chinese Journal of Chemical Physics》2005年第5期750-758,共9页化学物理学报（英文）

基　　金：ProjectsupportedbytheEastChinaInstituteofTechnolodgy(DHS0429;DHB0406).

摘　　要：采用B3LYP/6-31G**的方法在Gaussian03程序下对卟吩(PH2)、m-四氟卟啉(m-TFPH2)、β-八氟卟啉(β-OFPH2)和m-四氟,β-八氟卟啉(12FPH2)的结构进行几何优化,并进行振动分析.计算并讨论了PH2、m-TFPH2、β-OFPH2和12FPH2在内氢迁移反应中的反应物、产物、中间体、过渡态及二级鞍点的结构与能量.通过对结构和能量的比较,发现各物质内氢迁移反应均以异步历程进行,可见取代基对卟啉内氢迁移反应的历程选择没有影响.但取代基会影响同步历程和异步历程之间的速率差异.另外,氟取代基使得内氢迁移反应的异步历程的正负反应速率有所减小,起决定性作用的是取代基的电子效应,这些与化学直观也是相一致的.The structures and energies of reactant, product, intermediate, transition and second order saddlepoint in the transfer reaction of inner hydrogen atoms in porphine（ PH2 ） , m-tetra-fluorine-porphyrin（ m-TFPH2 ） , fl-octafluorine-porphyrin （β-OFPH2 ） and m-tetra-fluorine, fl-octa-fluorine-porphyrin（ 12FPH2 ） were calculated by using B3LYP/6-31G＊＊ method under certain symmetry restriction. In the transfer reaction of inner hydrogen atoms in all various matters, the comparison of structures and the energies shows that the probabilities of asynchronous mechanism are larger than that of synchronous mechanism via a second-order saddle-point, and substitutents to porphyrin in hydrogen migration have no influence on mechanism choice. But the substitutents can affect speed differences between the synchronous mechanisms and the asynchronous mechanisms. In addition, fluoro substitutents decrease speeds of positive and negative reactions in asynchronous mechanisms, which is in agreement with chemical intuition.

关 键 词：内氢迁移(NH的互变异构化) 过渡态 二级鞍点 氟取代基 取代基效应 

分 类 号：O621.25[理学—有机化学]