Theoretical study on the mechanism of the NCOÂ +Â CH3 reaction

The reaction of NCO with CH3 is studied at B3LYP/6-11G(d,p) and CCSD(T)/6-311++G(3df,2pd) (single-point) levels. On the singlet potential energy surface (PES), the most feasible channel is direct radical-radical recombination leading to isomers OCNCH3 and NCOCH3. Further isomerization and dissociation of OCNCH3 and NCOCH3 to yield the dissociation products need to surmount the energy barrier at least 4.7 kcal/mol with respect to reactant, which indicate that these processes are kinetically unfeasible at normal temperatures and may become feasible only at high temperatures. Compared with the singlet pathways, the triplet pathways may have less contribution to the title reaction.