Theoretical Dynamic Studies on the Reaction of CH3C(O)CH3−nFn with the Hydroxyl Radical and the Chlorine Atom

• Published in: Chemphyschem 2006-08, Vol.7 (8), p.1741-1749
• Main Authors: Ji, Yue-Meng, Wang, Li, Li, Ze-sheng, Liu, Jing-yao, Sun, Chia-chung
• Format: Article
• Language: English
• Subjects: ab initio calculations; Atmospheric composition. Chemical and photochemical reactions; Chemical composition and interactions. Ionic interactions and processes; computer chemistry; density functional calculations; Earth, ocean, space; Exact sciences and technology; External geophysics; gas-phase reactions; kinetics; Meteorology; Physics of the high neutral atmosphere
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.200600143

The mechanisms of the reactions: CH3C(O)CH2F+OH/Cl→products (R1/R2) and CH3C(O)CF3+OH/Cl→products (R3/R4) are studied over a wide temperature range (200–2000 K) by means of the dual‐level direct dynamics method. The optimized geometries and frequencies of the stationary points are calculated at the MP2/cc‐pVDZ and B3LYP/6‐311G(d,p) levels. The energy profiles of the reactions are then refined with the interpolated single‐point‐energy method (ISPE) at the BMC‐CCSD level. The canonical variational transition‐state theory (CVT) with the small‐curvature‐tunneling (SCT) correction method is used to calculate the rate constants. Using group‐balanced isodesmic reactions as working chemical reactions, the standard enthalpies of formation for CH3C(O)CH2F, CH3C(O)CF3, CH3C(O)CHF, CH2C(O)CH2F, and CH2C(O)CF3 are evaluated at the CCSD(T)/6‐311+G(2d,p)//MP2/cc‐pVDZ level of theory. The results indicate that the hydrogen ion is dominated by removal from the fluoromethyl position rather than from the methyl position. Hydrogen ion: The mechanisms of the reactions: CH3C(O)CH2F+OH/Cl→products (R1/R2) and CH3C(O)CF3+OH/Cl→products (R3/R4) (see figure) were studied over a wide temperature range (200–2000 K) using the dual‐level direct dynamics method. The results indicate that the hydrogen ion predominantly takes place at the fluoromethyl position.