Lee Chen-Chi, Lin Mei-Ya, Lu Yu-Huan, Chen Hsin-Tsung
Department of Chemistry and Center for Nanotechnology, Chung Yuan Christian University , Chungli 32023, Taiwan.
J Phys Chem A. 2014 May 15;118(19):3395-401. doi: 10.1021/jp4127013. Epub 2014 May 1.
The mechanisms of radical-molecule reactions between HCO (formyl radical) and O3 (ozone) have been investigated by using BH&HLYP and QCISD methods with the 6-311++G(3df,2p) basis set. The energetics have been refined with CCSD(T) and QCISD(T) theoretical approaches with the same basis set based on the geometries calculated at the QCISD method. The intermediates of hydrogen-bonded complexes and the critical transition states are also examined with the multireference methods. Two possible reaction pathways containing hydrogen-abstraction and association-elimination processes for the interaction of HCO with O3 are proposed. Both reaction mechanisms can occur via the prereactive hydrogen-bonded complex, O3-HCO, with 2.45 kcal/mol stability at the CCSD(T) approach with respect to the reactants; even so, the hydrogen-abstraction mechanism exhibits a lower energy barrier. The rate constants for both processes are also predicted. The total rate constant at 298 K is calculated to be in close agreement with the experimental value of 8.3 × 10(-13) cm(3) molecule(-1) s(-1).
通过使用BH&HLYP和QCISD方法以及6-311++G(3df,2p)基组，对HCO（甲酰基自由基）与O3（臭氧）之间的自由基-分子反应机理进行了研究。基于在QCISD方法计算的几何结构，使用相同基组的CCSD(T)和QCISD(T)理论方法对能量进行了优化。还使用多参考方法研究了氢键复合物中间体和关键过渡态。提出了HCO与O3相互作用的两种可能反应途径，包括氢提取和缔合消除过程。两种反应机制都可以通过预反应氢键复合物O3-HCO发生，在CCSD(T)方法中相对于反应物具有2.45 kcal/mol的稳定性；即便如此，氢提取机制的能垒较低。还预测了两个过程的速率常数。计算得出298 K时的总速率常数与8.3×10(-13) cm(3) molecule(-1) s(-1)的实验值非常吻合。
