Theoretical study on the hydrogen abstraction reactions of CF3CHFCF3 and CF3CF2CHF2 with X atoms (X = F, Cl, and Br)

• The mechanisms of CF3CHFCF3/CF3CF2CHF2 with halogen are studied theoretically.
• The reactivity decreases in the order of F > Cl > Br.
• The dynamics properties are calculated by dual-level (X//Y) direct dynamics methods.

The reaction mechanisms of reactions CF3CHFCF3 and CF3CF2CHF2 with X atom (X = F, Cl, and Br) are studied theoretically. Moreover, the dynamics properties of reactions CF3CHFCF3/CF3CF2CHF2 + X (X = F and Cl) are calculated by dual-level (X//Y) direct dynamics methods. The electronic structure information is obtained at the lower level, i.e., MPW1K/6-311+G(d,p). Then, single-point energies are calculated by G3(MP2) method based on the lower level DFT geometries. Subsequently, the rate constants are evaluated using the variational transition-state theory (VTST) proposed by Truhlar and co-workers over a temperature range of 200–2000 K. The reactivity of reactions CF3CHFCF3/CF3CF2CHF2 with three halogen atoms (F, Cl, and Br) is compared. Our calculations show that the barrier heights of reactions CF3CHFCF3/CF3CF2CHF2 with F atom are much less than other reactions. So the rate constants of reactions CF3CHFCF3/CF3CF2CHF2 with F atom are greatly larger than those of other reactions. Finally, the non-linear Arrhenius expressions of reactions CF3CHFCF3/CF3CF2CHF2 + X (X = F and Cl) are presented to assistant further experiments.

Schematic pathways for the reactions CF3CHFCF3 + X (X = F, Cl, and Br). Relative energies with ZPE correction at the G3(MP2)//MPW1K/6-311+G(d,p) level are in kcal mol−1.Figure optionsDownload as PowerPoint slide