Theoretical studies on the reactions of CHF2CF2OCH3/CH2FCF2OCH3 with OH radicals

The hydrogen abstraction and displacement process of OH radicals with CHF2CF2OCH3 (R1) and CH2FCF2OCH3 (R2) are studied theoretically. Moreover, the secondary reactions of their products (CHF2CF2OCH2, CF2CF2OCH3, CH2FCF2OCH2, and CHFCF2OCH3) with OH radical are also carried out. Electronic structures of all stationary points are calculated at the BMK/6-311+G(d,p) level. And the single point energy calculation is performed using BMC-CCSD method to refine the reaction enthalpy and barrier height for each reaction channel. The correlation between the barrier height and the corresponding bond dissociation energy is studied. Using the canonical variational transition-state theory (CVT) including the small-curvature tunneling (SCT) correction, the rate constants for CHF2CF2OCH3/CH2FCF2OCH3 + OH reactions are calculated within 200–2000 K. The total rate constants calculated from the sum of the individual rate constants taking into account the Boltzmann distribution of each conformer. A good agreement is obtained between theoretical and experimental rate constants. Finally, the theoretical rate constants are fitted to four-parameter expression to assist further experimental study.

Schematic pathways for the reaction CHF2CF2OCH3 (SC11) + OH. Relative energies with ZPE at the BMC-CCSD//BMK/6-311+G(d,p) level are in kcal mol−1.Figure optionsDownload as PowerPoint slideHighlights
► The mechanisms of CHF2CF2OCH3/CH2FCF2OCH3 with OH radical are studied theoretically.
► The displacement processes are also considered.
► The dynamics properties are calculated by dual-level (X//Y) direct dynamics methods.