ClONO2异构化反应和分解反应的理论研究

用B3LYP/6 31+G(d)和MP2 (Full) /6 31+G(d)优化ClONO2 及其分解反应和异构化反应的过渡态和产物的分子结构 .在B3LYP/6 31+G(d)水平上计算了相关分子的振动频率 .ClONO2 的几何结构、振动频率和红外强度与实验测量值符合得很好 .找到了未曾报道的立体异构体 .对这一立体异构体进行了高级别理论方法CCSD(T) /6 311G(d)和QCISD(T) /6 311G(d)的几何结构优化和振动频率计算 ,表明它是一个稳定的立体异构体 .在所研究的几种反应中 ,ClONO2 分解为NO2 +ClO是最容易进行的反应 .而ClONO2 异构为立体异构体的反应是最难进行的反应 .其所需克服的过渡态的能垒为 4 81.5 2kJ/mol,而反应吸收能量为 2 99.85kJ/mol.次难进行的是ClONO2 经TS1到反应中间体M1,再经TS12而分解为ClNO +O2 的反应 .这个反应通道所需克服过渡态的能垒为 4 2 1.5 5kJ/mol,反应吸收能量为 15 7.98kJ/mol.从以上分析可知 ,和ClO +NO2 反应生成ClONO2 比较 ,ClONO2 具有较好的稳定性 .

Theoretical Study of Isomerization and Decomposition Reactions of ClONO2

The potential energy surface for the decomposition and isomerization of Chlorine Nitrate (ClONO_2) is calculated using the G3 theory. Geometries of related species are optimized at the MP2(full)/6-31+G(d) and B3LYP/6-31+G(d) level. Vibrational frequencies and IR intensities of ClONO_2 have been calculated at the same level. Obtained geometries and vibrational frequencies as well as IR intensities for ClONO_2 are in good agreement with experimental values. A new stable stereoisomer is verified by CCSD(T) and QCISD(T) methods at 6-311G(d) basis set. Calculated geometries using above methods for this stereoisomer are in accord with each other. The calculated reaction heat of ClONO_2 are also in good agreement with the available data in the literature. Among these reactions of ClONO_2, the stereoisomer reaction is the hardest one. The barrier height for this reaction is 481.52 kJ/mol relative to ClONO_2 and the reaction is endothermic by 299.85 kJ/mol. On the other hand, among these unimolecular reactions of ClONO_2, the decomposition reaction of NO_2 +ClO is the easiest one. These results indicate that ClONO_2 is very stable.