Potential Energy Surfaces for the Reaction of O Atoms with CH3I: Implications for Thermochemistry and Kinetics

The geometries of IO, HCIO, ICH2O, CH3IO, CH3OI, CH2IOH, and ICH2OH have been obtained at the HF and MP2(FU)/6-31G(d) levels of ab initio theory, and the HF/6-31G(d) frequencies are compared with experimental assignments where these are available. The Gaussian-2 method was used to provide thermochemical data for use in atmospheric and combustion modeling. Transition states that connect these species have also been characterized, and the results were used to develop the singlet and triplet potential energy surfaces for the reaction O(3P) + CH3I. These surfaces explain the complex behavior of this reaction, and a QRRK analysis over 200-2000 K gave good accord with recent kinetic and product studies by Gilles et al. [J. Phys. Chem. 1996, 100, 14005]. IO is predicted to be the dominant product below about 2000 K. Other likely products are OH and the collisionally stabilized adducts CH3IO and ICH2OH, and the latter’s fragmentation products that include H and HI.