Temperature dependences of the reactions of O(3P) atoms with selected chlorofluoroethenes between 298 and 359 K

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 vertical bar O(3P)vertical bar(0)<<vertical bar ethene vertical bar(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 cm(3) molecule(-1) s(-1)) were k(1) = (1.07 +/- 0.32) x 10(-11) expl-(8000 +/- 1600)/RT), k(2) = (0.56 +/- 0.10) x 10(-11) exp{-(8700 +/- 500)/RT}, k(3) =(4.23 +/- 1.25) x 10(-11) exp{-(12,700 +/- 800)/RT}, and k(4) = (1.13 +/- 0.62) x 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((3)p). (c) 2005 Wiley Periodicals, Inc.