Theoretical Study on the Reactions of (CF₃)₂CFOCH₃ + OH/Cl and Reaction of (CF₃)₂CFOCHO with Cl Atom

Abstract

Reactions of (CF3)2CFOCH3 and (CF3)2CFOCHO with hydroxyl radical and chlorine atom are studied at the B3LYP and BHandHLYP/6-311+G(d,p) levels along with the geometries and frequencies of all stationary points. This study is further refined by CCSD(T) and QCISD(T)/6-311+G(d,p) methods in the minimum energy paths. For the reaction (CF3)2CFOCH3 + OH, two hydrogen abstraction channels are found. The total rate constants for the reactions (CF3)2CFOCH3 + OH/Cl and (CF3)2CFOCHO + Cl are followed by means of the canonical variational transition state with the small-curvature tunneling correction. The comparison between the hydrogen abstraction rate constants by hydroxyl and chlorine atom is discussed. Calculated rate constants are in reasonable agreement with the available experiment data. The standard enthalpies of formation for the reactants, (CF3)2CFOCH3 and (CF3)2CFOCHO, and two products, (CF3)2CFOCH2 and (CF3)2CFOCO, are evaluated by a series of isodesmic reactions. The Arrhenius expressions for the title reactions are given as follows: k1= 1.08 × 10(-22) T(3.38) exp(-213.31/T), k2= 3.55 × 10(-22) T(3.61) exp(-240.26/T), and k3= 3.00 × 10 (-19) T(2.58) exp(-1294.34/T) cm(3) molecule(-1) s(-1).

Theoretical insight into OH- and Cl-initiated oxidation of CF3OCH(CF3)2 and CF3OCF2CF2H & fate of CF3OC(X•)(CF3)2 and CF3OCF2CF2X• radicals (X=O, O2)

“…This will be borne out in the following study. The above conclusion about potential energy curves is similar with the previous theoretical work about the reactions of HFEs with OH radicals or Cl atoms8101213141516. The following study of the rate constants will also support this view deeply.…”

“…Taking reaction 8 as an example, the specific values of CVT/SCT and CVT rate constants are 152.29, 32.35, 4.77, and 1.61 at 230, 296, 500, and 1000 K, respectively. In the theoretical study on reactions of (CF 3 ) 2 CFOCH 3 , CF 3 CHFOCF 3 , CHF 2 OCHFCF 3 121415 with OH radicals and Cl atoms, similar tunneling effects can be found. Figure S6b shows that the CVT/SCT and CVT rate constants almost superposed on each other, implying that the tunneling contribution can be ignored for reaction 6.…”

“…However, the TS2 is product-like, and reaction 6 may proceed via late transition state. This phenomenon also appears in some similar species (CHF 2 OCF 2 CH 2 F, (CF 3 ) 2 CHOCH 3 , (CF 3 ) 2 CFOCH 3 , CF 3 CHFOCH 3 , CF 3 CHFOCF 3 , CHF 2 OCHFCF 3 , CF 3 OCH 2 CHF 2 , CF 3 OCHFCHF 2 )8912−16 reaction with OH radicals or Cl atoms.…”

“…We also calculated enthalpies of formation () for the species CF 3 OCH(CF 3 ) 2, CF 3 OC(CF 3 ) 2 , CF 3 OCF 2 CF 2 H (a, b), and CF 3 OCF 2 CF 2 (a, b) by the reactions 16–27. The experimental enthalpies of formation () values9111214 involved in the reactions 16–27 are listed in Table S5. The enthalpies of formation () for the species CF 3 OCH(CF 3 ) 2, CF 3 OC(CF 3 ) 2, CF 3 OCF 2 CF 2 H (a), CF 3 OCF 2 CF 2 (a), CF 3 OCF 2 CF 2 H (b), and CF 3 OCF 2 CF 2 (b) are −525.61, −467.24, −412.89, −361.86, −412.88, and −361.70, respectively.…”

“…During these years, many theoretical91011121314151617 and experimental181920212223 investigations about the reactions of some volatile organic compounds (VOCs) with free radicals have been carried out in kinetic properties, reaction mechanisms, temperature dependence and more. Previous studies have generally evaluated the fates of HFEs at 298 ± 2 K only.…”