The geometries of reactants, transition states, intermediates and products on the reaction of CH2CH(2A') + O_3 have been optimized at the MP2 (full)/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 QCISD (T, full)/6-311 + + G** level, based on the MP2(full)/6-311 + + G** optimized structures. The zero point energy (ZPE) corrections and the rate constants of reaction were also obtained. The results show that there are two reaction channels, CH2CH(2A') + O3→TS1→Ml→TS2→ O2 + OCH2CH→TS4 + O2→O2(3∑g) + CH2CHO(2A") and CH2CH(2A') + O3→M2→ TS3→O2(3∑g) + CH2CH0(2A"), respectively. The latter reacts more easily of which the reaction barrier is lower (2.97 kJ/mol) and reaction activity is higher. Therefore, the results of theoretical study indicate that CH2CH(2A') radicals in the atmosphere are able to greatly deplete ozone and the reaction of CH2CH (2A') radicals with ozone is strongly exothermic.

Key words: REACTION MECHANISM, TRANSITION STATE THEORY, FREE RADICAL REACTION, AB INITIO CALCULATION, ACTIVATION ENERGY, OZONE