CH_(3)O+HO_(2)反应机理和路径的理论研究  

Theoretical study on the mechanism and pathways of the CH_(3)O+HO_(2) reaction

作　　者：赵慧 路成刚[1] 唐沂珍[1] ZHAO Hui;LU Cheng-gang;TANG Yi-zhen(School of Environmental and Municipal Engineering,Qingdao University of Technology,Qingdao 266520,China)

机构地区：[1]青岛理工大学环境与市政工程学院,山东青岛266520

出　　处：《分子科学学报》2022年第5期415-423,共9页Journal of Molecular Science

基　　金：山东省重点研发项目(2018GSF117017,2019GSF109046);国家自然科学基金资助项目(41775119)。

摘　　要：采用量子化学方法在CCSD(T)/aug-cc-pvtz//ωB97XD/6-311++G(d,p)理论水平下,对CH_(3)O和HO_(2)自由基反应机理和产物进行了研究.计算结果表明,在单重态下,这2个自由基可以直接发生单电子结合反应生成中间体CH_(3)OOOH,随后进一步分解生成CH_(2)O_(2)+HO_(2),CH_(3)OH+O_(2),CH_(2)O+HO_(2)O_(2),CHO_(4)+O_(3)和CH_(2)O+HO_(2)+O;同时,还可以发生直接氢抽提反应生成CH_(3)OH+O_(2),其能垒为47.7 kJ·mol^(-1),是单重态反应的主要产物.在三重态下存在2条氢抽提反应,HO_(2)直接抽提CH_(3)O的H原子生成CH_(2)O^(T)+HO_(2)^(T),CH_(3)O抽提HO_(2)的H生成CH_(3)OH^(S)和O^(T),能垒为6.5 kJ·mol^(-1),为三重态反应的主要产物.此外,含时密度泛函理论计算表明在太阳光照射下中间体CH_(3)OH不发生光解.最佳反应路径R8在298 K,1.01×10^(5) Pa条件下的反应速率常数为2.1×10^(-13)cm^(3)·molecule^(-1)·s^(-1).CH_(3)O is an important atmospheric species generated during the photo-oxidation of hydrocarbons.It is directly involved in the catalytic cycle of Oloss in the stratosphere,and is also important in atmospheric chemical reactions and combustion chemistry.On the other hand,HO_(2)is not only a key oxidizing radical in the atmospheric environment,but also plays an important role in the elimination of pollutants.Therefore,the reaction of CH_(3)O and HO_(2)radicals is expected to explore the reaction process in the atmospheric environment.In the oxygen-rich state,the products of methanol combustion include CH_(3)OH,CH_(3)O and HO_(2).Theoretical study on the oxidation products of the reaction of CH_(3)O and HO_(2)is not detailed yet.The reaction mechanism and products of CH_(3)O and HO_(2)reaction were investigated using quantum chemical methods.The geometries of the reactants(R),products(P),intermediates(IM),and transition states(TS)were optimized at theωB97 XD/6-311++G(d,p)level of theory.Harmonic vibrational frequency calculations were performed at the same level of theory to determine the nature of the various stationary points,as well as zero-point-energy(E)corrections.Single-point energy calculations were performed by the higher-level electron-correction method CCSD(T)with the basis set aug-cc-pvtz.In the singlet state reaction,the calculations show that the two radicals can directly undergo single-electron binding reactions to form the intermediate CH_(3)OOOH,which has two conformers with the relative energy of 67.3 and 78.3 kJ·molfor cis-and trans-CH_(3)OOOH,respectively.After formed it may take place further decomposition reactions to form CH_(2)O_(2)+HO_(2),CH_(3)OH+O_(2),CH_(2)O+HO_(2)O_(2),CHO_(4)+O_(3)andCH_(2)O+HO_(2)+O.Besides,a direct hydrogen abstraction reaction can occur to form CH_(3)OH+Owith an energy barrier of 47.7 kJ·mol^(-1),which is the main product of the singlet state reaction.The second feasible channel starts from trans-CH_(3)OOOH with the O—O bond connecting to C—O bond and C—H b

关 键 词：CH_(3)O HO_(2) 反应机理 量子化学 反应速率常数 

分 类 号：O641[理学—物理化学]