Computational study of oxygen atom (3P and 1D) reactions with CF3CN

Singlet and triplet potential energy surfaces for the reactions of oxygen atoms (3P and 1D) with CF3CN have been studied computationally to evaluate the reaction mechanisms, possible products, and rate constants. On the triplet surface, six kinds of pathway are revealed, namely: direct fluorine abstraction, C-addition/elimination, N-addition/elimination, substitution, insertion and F-migration. The results show that the reaction should occur mainly through the C-addition/elimination mechanism involving the chemically activated CF3C(O)N* intermediate, and the major products are CF3 and NCO. The rate constants for C-addition/elimination channel of the reaction of O(3P) with CF3CN have been determined by using RRKM statistical rate theory and compared with the experimental data. On the singlet surface, the atomic oxygen can easily insert into the C–F or C–C bond of CF3CN, forming the insertion intermediates FOCF2CN and CF3OCN, and O(1D) can add to the carbon or nitrogen atom of the CN group in CF3CN, forming the addition intermediates CF3C(O)N and CF3CNO; both approaches are found to be barrierless. The decomposition and isomerization of some intermediates were also modeled at the QCISD(T)/6-311+G(2df)//B3LYP/6-311+G(d) level for the better understanding of the O(1D) with CF3CN chemistry. The decomposition products CF3 and NCO arising from CF3OCN and CF3NCO are the dominant species. Further comparison with similar reactions is also summarized.