Can a Single Water Molecule Really Affect the Hydrogen Abstraction Reaction of HO2+NO2 under Tropospheric Conditions?

ion Reaction of HO2+NO2 under Tropospheric Conditions? Tianlei Zhang a,∗ , Rui Wang a , Hao Chen a , Suotian Min a , Zhiyin Wang a , Caibin Zhao a , Qiong Xu a , Lingxia Jin a , Wenliang Wang b, * , Zhuqing Wang c a School of Chemical & Environment Science, Shaanxi University of Technology, Hanzhong, Shaanxi 723001, China b Key Laboratory for Macromolecular Science of Shaanxi Province, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi’an, Shaanxi 710062, China c Shandong Provincial Key Laboratory of Ocean Environment Monitoring Technology, Shandong Academy of Sciences Institute of Oceanographic Instrumentation, Qingdao 266001, China. Abstract The effect of a single water molecule on the hydrogen abstraction reaction of HO2 +NO2 has been investigated by employing B3LYP and CCSD(T) theoretical approaches in connection with the aug-cc-pVTZ basis set. The reaction without water has three kinds of reaction channels on both singlet and triplet potential energy surfaces depending on how the HO2 radical approached NO2, corresponding to the formation of trans-HONO+O2, cis-HONO+O2 and HNO2+O2. Our calculated results show that triplet reaction channels are favorable and their total rate constant, at 298 K, is 2.01 ×10 cm⋅molecule⋅s in good agreement with experimental values. A single water molecule affects each one of these triplet reaction channels in three different reactions of H2O···HO2+ NO2, HO2···H2O+ NO2 and NO2···H2O+ HO2, depending on the way the water interacts. Interestingly, the water molecule in these reactions not only acts as a catalyst giving the same products as the naked reaction, but also as a reactant giving the product of HONO2+H2O2. The total rate constant of H2O···HO2+ NO2 reaction is estimated to be slower than the naked reaction by 6 order of magnitude at 298 K. However, the total rate constant of HO2···H2O+ NO2 and NO2···H2O+ HO2 reaction is respectively faster than the naked reaction by 4 and 3 orders of magnitude at 298 K, and their total effective rate constant is predicted to be 1.2 times than the corresponding total rate constant without water at 298 K, which is agreement with the predication reported by Li et al (science, 2014, 344, 292-296).