Mechanism, kinetics and atmospheric fate of CF3CH=CH2, CF3CF=CH2, and CF3CF=CF2 by its reaction with OH-radicals: CVT/SCT/ISPE and hybrid meta-DFT methods.

The dual level direct dynamic study is carried out for the reactions of CF3CH=CH2, CF3CF=CH2 and CF3CF=CF2 with hydroxyl radicals. The dynamic calculations are performed using the variational transition state theory (VTST) with interpolated single-point energies (ISPE) method at M06-2X/MG3S//M06-2X/6-31+G(d,p) level of theory. All the possible reactions such as abstraction and addition-elimination pathways are explored for the title reactions. The temperature dependent rate coefficients using canonical variational transition state theory with small curvature tunneling for the reaction of OH radicals with test molecules over the temperature range of 200-3000 K are computed. The predicted rate coefficients (in 10⁻¹² cm³ molecule⁻¹ s⁻¹) using CVT/SCT/ISPE methodology for the reaction of CF3CH=CH2, CF3CF=CH2 and CF3CF=CF2 with OH radicals are 1.48, 1.02 and 1.77, respectively, are in good agreement with reported ones at 298 K. The atmospheric lifetimes for the test molecules CF3CH=CH2, CF3CF=CH2 and CF3CF=CF2 are calculated at 277 K to be 8, 11 and 6 days, respectively. Global warming potentials are also reported for the different time horizon of 20, 100 and 500 years.