POTENTIAL-ENERGY SURFACES FOR THE REACTION OF O-ATOMS WITH CH3I - IMPLICATIONS FOR THERMOCHEMISTRY AND KINETICS

The geometries of IO, HClO, ICH2O, CH3IO, CH3OI, CH2IOH, and ICH2OH ha ve been obtained at the HF and MP2(FU)/6-31G(d) levels of ab initio th eory, and the HF/6-31G(d) frequencies are compared with experimental a ssignments where these are available. The Gaussian-2 method was used t o provide thermochemical data for use in atmospheric and combustion mo deling. Transition states that connect these species have also been ch aracterized, and the results were used to develop the singlet and trip let potential energy surfaces for the reaction O(P-3) + CH3I. These su rfaces explain the complex behavior of this reaction, and a QRRK analy sis over 200-2000 K gave good accord with recent kinetic and product s tudies by Gilles ct al, [J. Phys, Chem. 1996, 100, 14005], IO is predi cted to be the dominant product below about 2000 K, Other likely; prod ucts are OH and the collisionally stabilized adducts CH3IO and ICH2OH, and the latter's fragmentation products that include H and HI.