Absolute rate determinations and temperature dependences of the gas-phase reactions of O(3P) with halogenated propenes

The rate constants for the gas-phase reactions of ground state oxygen atoms with CF3CHCH2 (1), CF3CFCF2 (2) and CF3CClCCl2 (3) have been measured directly using a discharge flow tube employing the O(3P) chemiluminescence titration method. The experiments were carried out under pseudo-first-order conditions with [O(3P)]0 ≪ [propene]0. The temperature dependences of the reactions were studied for the first time in the range 298-363 K. The Arrhenius expressions obtained (in units of cm3 molecule−1 s−1) were: k1 = (0.28 ± 0.09) × 10−11 exp[−(10.4 ± 0.9) × 103/RT], k2 = (1.57 ± 0.72) × 10−11 exp[−(15.6 ± 1.3) × 103/RT], k3 = (2.23 ± 1.27) × 10−11 exp[−(16.0 ± 1.6) × 103/RT]. All the rate coefficients display a positive temperature dependence which points to the importance of the irreversibility of the addition mechanism for these reactions. Halogen substitution in the alkenes is discussed in terms of reactivity with O(3P) and its relation with the ionization potential.