2-氯吡啶光氯化夺氢反应机理的量子化学研究

Theoretical Study on the Extracting Hydrogen Mechanism of Gaseous Phase Photochemical Chlorination of 2-Chloropyridine

用PM3方法研究了2-氯吡啶光氯化夺氢反应生成不同氯代产物的两个主要基元反应过渡态,并计算比较了不同反应路径活化能的高低.结果表明,不同产物以生成2,6-二氯吡啶的活化能最低.生成2,6-二氯吡啶两个连续的基元反应的活化能分别为9.43和15.56kJ/mol,反应优先生成2,6-二氯吡啶.

The extracting hydrogen mechanism of 2-chloropyridine reacting with chlorine radical mainly consists of two elementary reactions which obtained four different dichlorinated products. The activation barrier, reaction heat and the structure of the transition state for different paths of the reaction were studied by semi-empirical(PM3) method. The results showed that the second elementary reaction was the key step to the reaction of rate, and its activation barrier leading to 2,6-dichloropyridine was the lowest among the four reaction paths. The activation barriers of the two consequent elementary reactions are 9.43 and 15.56 kJ/mol, respectively. Therefore, 2,6-dichloropyridine was the prior product theoretically, which was in agreement with the experimental results.