Mechanistic and kinetic study on the reaction of methylperoxy radical with atomic iodine

Singlet and triplet potential energy surfaces for the CH₃O₂ with I reaction have been investigated computationally to propose the reaction mechanisms and possible products. Multichannel RRKM theory and transition-state theory have been used to compute the overall and individual rate constants at 200-3000K and 10^-14-10¹⁴Torr. On the singlet PES, addition-elimination, substitution and H-abstraction mechanisms are located, and the addition-elimination mechanism is dominant. At 70Torr with N₂ as bath gas, IM1(CH₃OOI) formed by collisional stabilization is dominated at 200-300K, whereas CH₂O and HIO are the major products at the temperatures between 350 and 3000K; The title reaction exhibits the typical falloff behavior. The results show that temperature and pressure affect the yield of products. Furthermore, the predicted rate constants at 298K 70Torr of N₂ agree well with the available experimental values. On the triplet PES, the most favorable product should be CH₃I+O₂(³Σ) at atmospheric condition. Other two pathways on the triplet PES will not compete with the pathways on the singlet PES in kinetically and thermodynamically.