C2H与HO2双自由基反应的密度泛函理论研究

应用量子化学从头算和密度泛函理论(DFT)对C₂H与HO₂双自由基的单重态反应进行了研究.在UB3LYP/6-311G水平上优化了反应通道上各驻点(反应物、中间体、过渡态和产物)的几何构型.在CCSD(T)/6-311G^{**水平上计算了各物种的单点能,并对总能量进行了零点能校正.研究结果表明,反应物中自由基C₂H的边端C进攻自由基HO₂的边端O是主要的进攻方式.首先形成了中间体1(HCCOOH),由此经过不同的反应通道可以得到主要产物P1,次要产物P2,P3和P5.生成P1的反应热为-814.40kJ/mol.自由基C₂H的中间C进攻自由基HO₂的边端O是次要的进攻方式,可以得到产物P4和P6.根据势能面分析,所有反应均是放热反应.}

Theoretical Study on the Reaction of Ethynyl Radical with HO2 Radical by Density Functional Theory

Using DFT/UB3LYP and CCSD(T) methods, the reaction ethynyl radical with HO_2 radical was studied. At UB3LYP/6-311G~** level, the geometries of stationary points(reactants, transition states, intermediates and products) were optimized, respectively, and single-point calculations are performed at the CCSD(T)/6-311G~** level by using the UB3LYP/6-311G~** optimized geometries. All the energies of the species were obtained at the CCSD(T)/6-311G~** level with inclusion of UB3LYP/6-311G~** zero-point vibrational energies(ZPVE). The calculated results suggest that the attacking of the end C atom of C_2H radical to the end O atom of HO_2 radical is the most predominant initial step for the title reaction. From intermediate 1(HCCOOH) formed in the initial step, the main product P1~(CO+H_2CO) can be produced, as well as the secondary important products, P2, P3, P5. The reaction heat of generating P1 is {-814.40} kJ/mol. While the middle C of the ethynyl radical attacking the end O of the HO_2 radical should be the secondary, and the products P4 and P6 are obtained. By the analysis of the potential energy surface, we can draw the conclusion that all the reactions are exothermic reactions.