HO2 + ClO气相反应机理及主通道速率常数的理论研究

Theoretical studies of the HO2+ClO reaction mechanism and rate constants of major channel in the gas phase

摘要:

本文采用CCSD(T)/aug-cc-pVTZ//B3LYP/6-311+G(2df,2p)方法构建了HO2 + ClO反应体系的单、三重态反应势能剖面，并对该反应主通道的速率常数进行了计算研究。结果表明，HO2 + ClO反应中存在4条抽氢通R1 (HOCl + 1O2)、R2 (HOCl + 3O2)、R3 (HCl + 1O3)和R4 (HCl + 3O3)以及2条抽氧通道R5 (OOCl + HO)和R6 (OClO + HO)，其中抽氢通道R2 (HOCl + 3O2)和R3 (HCl + 1O3)的能垒比其它四个通道的能垒降低了9.08~42.90 kcal∙mol-1，是标题反应的优势通道。采用传统过渡态理论并结合Wigner校正对优势通道R2 (HOCl + 3O2)和R3 (HCl + 1O3)在240~425 K范围内的速率常数进行了计算。计算结果表明，通道R2 (HOCl + 3O2)的速率常数比R3 (HCl + 1O3)的对应值大了3~5个数量级，表明标题反应的速率主要取决于通道R2 (HOCl + 3O2)。此外在298 K时，通道R2 (HOCl + 3O2)的速率常数为2.76×10-15 cm3molecule-1s-1，与实验值较为吻合。

Abstract:

The mechanism for the reaction of ClO with HO2 was investigated at the CCSD(T)/aug-cc-pVTZ //B3LYP/6-311+G(2df,2p) level on both the singlet and triplet potential energy surfaces, along with the rate constant calculations of the major channel. The results show that there are four hydrogen abstraction channels, namely Channel R1 (HOCl + 1O2), Channel R2 (HOCl + 3O2), Channel R3 (HCl + 1O3) and Channel R4 (HCl + 3O3), as well as two oxygen abstraction channels, labeled as Channel R5 (OOCl + HO) and Channel R6 (OClO + HO) in the HO2 + ClO reaction. The energy barrier of the hydrogen abstraction Channels R2 (HOCl + 3O2) and R3 (HCl + 1O3) are lower by 9.08~42.90 kcal∙mol-1 than those of the other four channels. The rate constants of the favorable channels R2 (HOCl + 3O2) and Channel R3 (HCl + 1O3) in the 240~425 K range were evaluated by means of the classical transition state theory (TST) with Wigner tunneling correction. The calculated results show that the rate constant of Channel R2 (HOCl + 3O2) is larger by 3~5 orders of magnitude, indicating that the total rate constants of HO2 + ClO reaction mainly lie on the contribution of channel R2 (HOCl + 3O2). Besides, the rate constant of channel R2 (HOCl + 3O2) is 2.76×10-15 cm3molecule-1s-1 at 298 K, in excellent agreement with experimental value.