NAD(P)H辅酶模型还原碳正离子反应的研究——动力学、热力学及反应机理

Investigation on the Reduction of Carbocations by BNAH——Kinetics, Thermodynamics,and Reaction Mechanisms

本文对NAD(P)H模型物BNAH同呫吨正离子反应的动力学进行了较为详尽的测定.同位素效应,自由基抑制剂对反应的影响以及对不同机理模式中各基元步骤的热力学趋动力的研究均表明,反应由决速的电子转移引发,随后通过快速的氢原子转移而形成产物动力学活化参数的分析指出,电子转移前反应底物间首先形成一个预配合平衡.本文还对BNAH还原9-苯基呫吨正离子和三苯甲烷正离子的机理进行了较合理的估测.

The reduction of xanthylium cation by BNAH has been thoroughly investigated. The observed kinetic isotope effect, radical inhibitor (DNB) effect, and the driving forces for each mechanistic step in various mechanisms indicate that the reaction proceeds via an initial rate -determining electron transfer and is followed by a fast hydrogen atom abstraction. The kinetic activation parameters measured in this work show that there is a preequilibrium between two reactants prior to the electron transfer. The mechanisms of the reductions of 9 -phenylxanthylium and triphenylmethylium cations by BNAH are also discussed.