Computational study of oxygen atom ((3)P and (1)D) reactions with CF(3)CN.

Singlet and triplet potential energy surfaces for the reactions of oxygen atoms ((3)P and (1)D) with CF(3)CN 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 CF(3)C(O)N* intermediate, and the major products are CF(3) and NCO. The rate constants for C-addition/elimination channel of the reaction of O((3)P) with CF(3)CN 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 CF(3)CN, forming the insertion intermediates FOCF(2)CN and CF(3)OCN, and O((1)D) can add to the carbon or nitrogen atom of the CN group in CF(3)CN, forming the addition intermediates CF(3)C(O)N and CF(3)CNO; 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((1)D) with CF(3)CN chemistry. The decomposition products CF(3) and NCO arising from CF(3)OCN and CF(3)NCO are the dominant species. Further comparison with similar reactions is also summarized.