The Quantum Study on the Photochemical Chlorination Mechanism of Pyridine

HAO Jinku, YANG Encui, WANG Wande, ZHAO Xiaojun, CAO Yingyu, WANG Yuxin
(School of Chemistry and Life Science, Tianjin Normal University, Tianjin 300074)

Abstract The addition mechanism of pyridine reacting with chlorine radical has been studied theoretically by semi-empirical PM3 and ab initio DFT B3LYP/3-21G*，6-31G* methods. For three different reaction paths leading to ortho, meta, para-chloropyridine, two transition states have been located by PM3 on each reaction path, while only one transition state by ab initio, however both methods give the same results: the energy of transition state and activation barrier on producing 2-chloropyridine are the lowest among three reaction paths, so 2-chloropyridine is obtained priorly, which agrees with the experimental results.
Key words Pyridine， Photochemical chlorination， Reaction mechanism， PM3， ab initio

吡啶光氯化反应机理的量子化学研究

郝金库 杨恩翠 王万得 赵小军 曹映玉 王玉新
(天津师范大学化学与生命科学学院 天津 300074)

摘要 半经验PM3方法和从头算 DFT B3LYP/3-21G*,6-31G*方法分别研究了氯自由基与吡啶分子发生加成反应的反应机理。生成邻、间、对氯代吡啶三条不同反应途径PM3方法优化得到两个过渡态，而从头算方法中只优化得到一个过渡态。但两种方法的研究结果均表明：三条反应途径中生成2-氯吡啶的过渡态能量和活化能最低，因此反应优先生成2-氯吡啶，与实验结果一致。
关键词 吡啶 光氯化 反应机理 PM3 从头算