水分子催化HCl+NO_3反应机理及动力学性质的理论研究

Theoretical Study on the Mechanism and Kinetics for Water-Catalyzed HCl + NO_3 Reaction

本文采用CCSD(T)/aug-cc-pVTZ//UB3LYP/6-311+G(2d,p)方法对HCl+NO_3反应机理及速率常数进行了研究,并在此基础上考虑了水分子对该反应的影响。研究结果表明,HCl+NO_3反应经历了生成产物为Cl+HNO_3的通道,克服了13.67kcal·mol^(-1)的能垒。加入水分子后,所得的产物并没有发生改变,但势能面却比裸反应复杂得多,经历了NO_3…H_2O+HCl、H_2O…HCl+NO_3和HCl…H_2O+NO_3三条反应通道。其中通道HCl…H_2O+NO_3为水分子参与反应的优势通道。此外,该通道比相同温度下裸反应的速率常数k_(R1)提高了0.33×10~4~1.07×10~7倍,且在298K时,k’_(RW3)/k’_(total)已达到95.9%,说明此时在实际大气环境中水分子对NO_3+HCl反应有明显的影响。

In this article,the mechanism and rate constant for the reaction of HCl ＋ NO3 without and with a water molecule were studied at the CCSD（ T）/aug-cc-pVTZ//UB3LYP/6-311 ＋ G（ 2d,p） level of theory. The results show that there is only one channel for the NO3＋ HCl reaction,labeled as HNO3＋ Cl formation channel. When one water molecule is added,the product of the reaction does not change,but the potential energy surface of the reaction becomes quite complex,yielding three different channels of NO3…H2O ＋ HCl,H2O…HCl ＋ NO3 and HCl…H2O＋ NO3. Channel HCl … H2O ＋ NO3 is the dominant channel for water molecules to participate in the reaction.Besides,the rate constant of HCl…H2O ＋ NO3 channel is predicted to be faster by 0. 33 × 10^4^ 1. 07 × 10^7 times than that of the NO3＋ HCl naked reaction. Its effective rate constant k＇（RW3）/k＇（totalis） up to 95. 9% at 298 K,that is,the single water molecule has a obvious influence on the atmospheric reaction of NO3＋ HCl.