TEMPERATURE DEPENDENCE OF THE REACTIONS OF O(3P) ATOMS WITH SELECTED CHLOROFLUOROETHENES BETWEEN 298 AND 360 K

TERUEL, MARIANO A.; COMETTO, PABLO M.; TACCONE, RAÚL A.; LANE, SILVIA I.

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS

Año: 2005 p. 763 - 769

0538-8066

The rate constants for the gas-phase reactions of ground-state oxygen atoms with CF2=CFCl (1), (E/Z)-CFCl=CFCl (2), CFCl=CH2 (3), and (E/Z)-CFH=CHCl (4) have been measured directly using a discharge flow tube coupled to a chemiluminescence detection system. The experiments were carried out under pseudo-first-order conditions with [O(3P)]0>>[alkene]0 . The temperature dependences of the reactions were studied for the first time in the range 298–359 K. The proposed Arrhenius expressions (in units of cm3 molecule-1 s-1) were k1 = (1.07 ± 0.32) × 10-11 exp{-(8000 ± 1600)/RT}, k2 = (0.56 ± 0.10) × 10-11 exp{-(8700 ± 500)/RT}, k3 = (4.23 ± 1.25) × 10-11 exp{-(12,700 ± 800)/RT}, and k4 = (1.13 ± 0.62)×10-11 exp{-(10,500±1500)/RT}. All the rate coefficients display a positive temperature dependence, which highlights the importance of the irreversibility of the addition mechanism for these reactions. Halogen substitution in the ethene is discussed in terms of reactivity with O(3P). The rate constants for the gas-phase reactions of ground-state oxygen atoms with CF2=CFCl (1), (E/Z)-CFCl=CFCl (2), CFCl=CH2 (3), and (E/Z)-CFH=CHCl (4) have been measured directly using a discharge flow tube coupled to a chemiluminescence detection system. The experiments were carried out under pseudo-first-order conditions with [O(3P)]0>>[alkene]0 . The temperature dependences of the reactions were studied for the first time in the range 298–359 K. The proposed Arrhenius expressions (in units of cm3 molecule-1 s-1) were k1 = (1.07 ± 0.32) × 10-11 exp{-(8000 ± 1600)/RT}, k2 = (0.56 ± 0.10) × 10-11 exp{-(8700 ± 500)/RT}, k3 = (4.23 ± 1.25) × 10-11 exp{-(12,700 ± 800)/RT}, and k4 = (1.13 ± 0.62)×10-11 exp{-(10,500±1500)/RT}. All the rate coefficients display a positive temperature dependence, which highlights the importance of the irreversibility of the addition mechanism for these reactions. Halogen substitution in the ethene is discussed in terms of reactivity with O(3P).