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

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), β-octa-fluorine-porphyrin (β-OFPH2) and m-tetra-fluorine, β-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.