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

Abstract

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.