Theoretical study on reaction mechanism of the fluoromethylene radical with nitrogen dioxide

The complex doublet potential energy surface for the reaction of ¹CHF with NO₂, including 14 minimum isomers and 30 transition states, is explored theoretically at the B3LYP/6-311G(d,p) and CCSD(T)/6-311G(d,p) (single-point) levels of theory. The initial association between ¹CHF and NO₂ is found to be the carbon-to-middle-nitrogen attack forming an energy-rich adduct a (HFCNO ₂) with no barrier, followed by concerted O-shift and C - N bond rupture leading to product P₂ (NO + HFCO), which is the most abundant In addition, a can take a 1,3-H-shift to isomer b (FCN(O)OH) followed by the dissociation to form the second feasible product P₄ (OH + FCNO). The least favorable pathway is that b undergoes a concerted OH-shift to form d (HO(F)CNO), which will dissociate to product P₅ (HF+OCNO) via side HF-elimination. The secondary dissociation of P₅ may form product P₇ (HF+NO+CO) easily. Furthermore, the ¹CHF attack at the end-O of NO₂ is a barrier-consumed process, and thus may only be of significance at high temperatures. The comparison with the analogous reactions ₁CHCl + NO₂ is discussed. The present study may be helpful for probing the mechanism of the title reaction and understanding the halogenated carbine chemistry.