Kinetics of the gas‐phase reactions of Cl atom with selected C2–C5 unsaturated hydrocarbons at 283 < T < 323 K

The reaction of Cl atoms with a series of C₂–C₅ unsaturated hydrocarbons has been investigated at atmospheric pressure of 760 Torr over the temperature range 283–323 K in air and N₂ diluents. The decay of the hydrocarbons was followed using a gas chromatograph with a flame ionization detector (GC‐FID), and the kinetic constants were determined using a relative rate technique with n‐hexane as a reference compound. The Cl atoms were generated by UV photolysis (λ ≥ 300 nm) of Cl₂ molecules. The following absolute rate constants (in units of 10^?11 cm³ molecule^?1 s^?1, with errors representing ±2σ) for the reaction at 295 ± 2 K have been derived from the relative rate constants combined to the value 34.5 × 10^?11 cm³ molecule^?1 s^?1 for the Cl + n‐hexane reaction: ethene (9.3 ± 0.6), propyne (22.1 ± 0.3), propene (27.6 ± 0.6), 1‐butene (35.2 ± 0.7), and 1‐pentene (48.3 ± 0.8). The temperature dependence of the reactions can be expressed as simple Arrhenius expressions (in units of 10^?11 cm³ molecule^?1 s^?1): k_ethene = (0.39 ± 0.22) × 10^?11 exp{(226 ± 42)/T}, k_propyne = (4.1 ± 2.5) × 10^?11 exp{(118 ± 45)/T}, k_propene = (1.6 ± 1.8) × 10^?11 exp{(203 ± 79)/T}, k_1‐butene = (1.1 ± 1.3) × 10^?11 exp{(245 ± 90)/T}, and k_1‐pentene = (4.0 ± 2.2) × 10^?11 exp{(423 ± 68)/T}. The applicability of our results to tropospheric chemistry is discussed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 478–484, 2000