Abstract: The mechanism of the reaction CH₃O ₂^·+NO CH₃O ·+NO₂ in gas phase has been studied bYUsing density functional theory. The geometries of reactants, transition states, intermediates and products have been optimized by B3LYP/6-31G ^* and HF/6-31G^* basis set. Transition states and intermediates have been verified by frequency analysis. The reaction path has been traced by Fukui′s theory of intrinsic reaction coordinate(IRC), with the change of geometry parameter being computed. In order to obtain credible energy, single points energy has been calculated by QCISD methods using the 6-311G^** basis set with zero-point energy correction done by B3LYP method. The isomerizations of the intermediates and the charge densities have been analyzed. The results show that the whole reaction comes through many courses, and it is an endothermic reaction with 50.93 kJ/mol endothermic value calculated. Among the three reaction paths proposed, the triplet state reaction is the most probable one with the lowest activation energy of 163.31 kJ/mol. This work will provide the important theoretical foundation for protecting theozonosphere and atmosphere.

Key words: CH₃O ₂^·+NO, Density functional theory, Reaction mechanism