吡啶光氯化反应机理的量子化学研究(II)——PM3计算吡啶光氯化反应体系能量与反应动力学分析

用量子化学方法 PM3结构参数全优化方法对吡啶光氯化反应所涉及的分子、自由基进行了能量计算 ,得到键解离能 ,并对反应活化能与动力学进行分析 .对吡啶光氯化反应 ,提出了氯自由基直接进攻吡啶环的碳原子和氯自由基首先夺取与吡啶环键链的氢原子两种不同的反应机理 .量化计算结果表明 :吡啶光氯化反应中夺氢反应机理所需的反应活化能较低 ,不同产物以生成2 -氯吡啶的活化能最低 ,为 1 74.0 8k J/mol,总反应级数为 1 .5级 ,对吡啶的分级数为 1级 .对氯气的分级数为 0 .5级 .

The Quantum Chemistry Study on Photochemical Chlorination of Pyridine (II) the Energy Calculation of the system by PM3 and Analysis of Kinetic Process

All the equilibrium structures in the photochemical chlorination of pyridine were optimized by PM3.As a result,activation energies were calculated and kinetic process were discussed with bond dissociation energies. The Addition mechanism and abstraction mechanism were discussed. The activation energies in three reaction channels of getting 2 chloropyridine, 3 chloropyridine and 4 chloropyridine were compared,too. The results showed that: the abstraction mechanism dominated the photochemical chlorination of pyridine and produced 2 chloropyridine priorly, the activation energies of producing 2 chloropyridine was 174.08kJ/mol,the overall order is 1.5,1 for pyridine and 0.5 for Cl 2.