CCl_2与CH_2O插入反应机理及热力学与动力学特性的理论研究

Theoretical Study on Mechanism and Characters of Thermodynamics and Kinetics of the Insertion Reaction of CCl_2 into CH_2O

采用密度泛函B3LYP/6-311G*和高级电子相关耦合簇[CCSD(T)/6-311G*]方法计算研究了CCl2与CH2O的插入反应机理,全参数优化了反应势能面各驻点的几何构型,用内禀反应坐标(IRC)和频率分析方法,对过渡态进行了验证.研究结果表明:反应(1)是单重态二氯卡宾与甲醛插入反应的主反应通道.该反应由两步组成:(i)两反应物首先经一无能垒的放热反应,放出9.73kJ·mol-1的热量,生成一中间体IM1,(ii)中间体IM1经一过渡态TS1,发生H的转移,生成产物P1,其势垒为47.32kJ·mol-1.用RRKM-TST理论计算了300～1900K温度范围内反应(1)的压力效应.用经Wigner校正的Eyring过渡态理论研究了不同温度下该反应的热力学和动力学性质.从热力学和动力学角度综合分析,在高压限101325Pa下,该反应进行的适宜温度范围为400～1800K,如此,反应既有较大的自发趋势和平衡常数,又具有较快的反应速率.

The insertion reaction mechanism of CCl2 into CH2O has been studied by using the B3LYP/6-311G＊ and CCSD（T）/6-311G＊ at single-point. The geometries of reactions, transition states and products were completely optimized. All the transition states were verified by the vibrational analysis and the internal reaction coordinate （IRC） calculations. The results show that the reaction （1） is the dominant reaction path, which proceeds via two steps： （i） two reactants form an intermediate （IM1）, which is an exothermal reaction of 9.73 kJ·mol^-1 without energy barrier, （ii） P1 is obtained via the TS1 and the H-shift, in which the energy barrier is 47.32 kJ·mol^-1. The pressure dependences of the total rate constant were calculated by applying RRKM-TST model in temperature range from 300 to 1900 K. The statistical thermody- namics and Eyring transition state theory with Wigner correction were used to study the thermodynamic and kinetic characters of this reaction. The results show that the appropriate reaction temperature rang is 400 to 1800 K at 1.0 Atm （101325 Pa）, in which the reaction has a bigger spontaneity capability, a larger equilibrium constant （K） and higher rate constant （k）.