CH_3(~2A')自由基与臭氧反应机理的量子化学研究

Quantum Study on the Reaction Mechanism of CH_3(~2A′) Radicals with Ozone Reaction

用量子化学UMP2方法,在6-311G基组水平上研究了CH3(2A')自由基与臭氧反应机理,全参数优化了反应过程中反应物、中间体、过渡态和产物的几何构型,在UQCISD(T)/6-311G水平上计算了它们的能量;并对它们进行了振动分析,以确定中间体和过渡态的真实性;同时应用经典过渡态理论计算了反应的速率常数,并与实验值进行了比较,CH3自由基与臭氧反应速率常数的理论计算结果为:4.73×10-14cm3·molecule-1·s-1,与实验报导的结果(k=2.52×10-14cm3·molecule-1·s-1)很接近,同时发现CH3(2A')自由基与O3的反应是强放热反应.

The geometries of reactants, transition states, intermediates and products on the reaction of CH3 ((2)A') + O-3 have been optimized at the UMP2/6-311++G** level. The transition states and intermediates of the reactions were verified by frequency analysis. The relative single-point energies were further calculated at the UQCISD(T)/6-311++G** level, based on the UMP2/6-311++G** optimized structures. The zero point energy (ZPE) corrections and reaction's rate constants were also obtained. We used the classic transition state theory to compute the rate constants of the CH3 ((2)A') + O-3 reaction( k = 4. 73 x 10(-14) cm(3) . molecule(-1) . s(-1)). Compared with the experimental values ( k = 2. 52 x 10(-14) cm(3) . molecule(-1) . s(-1)), our calculated result is in good agreement with experimental datum.