Rate coefficients for the reaction of the acetyl radical, CH3CO, with Cl2 between 253 and 384 K

Rate coefficients, k, for the gas‐phase reaction CH3CO + Cl2 → products (2) were measured between 253 and 384 K at 55–200 Torr (He). Rate coefficients were measured under pseudo‐first‐order conditions in CH3CO with CH3CO produced by the 248‐nm pulsed‐laser photolysis of acetone, CH3C(O)CH3, or 2,3‐butadione, CH3C(O)C(O)CH3. The loss of CH3CO was monitored by cavity ring‐down spectroscopy (CRDS) at 532 nm. Rate coefficients were determined by first‐order kinetic analysis of the CH3CO temporal profiles for [Cl2] < 1 × 1014 molecule cm−3 and the analysis of the CRDS profiles by the simultaneous kinetics and ring‐down method for experiments performed with [Cl2] > 1 × 1014 molecule cm−3. k2(T) was found to be independent of pressure, with k2(296 K) = (3.0 ± 0.5) × 10−11 cm3 molecule−1 s−1. k2(T) showed a weak negative temperature dependence that is well reproduced by the Arrhenius expression k2(T) = (2.2 ± 0.8) × 10−11 exp[(85 ± 120)/T] cm3 molecule−1 s−1. The quoted uncertainties in k2(T) are at the 2σ level (95% confidence interval) and include estimated systematic errors. A comparison of the present work with previously reported rate coefficients for the CH3CO + Cl2 reaction is presented. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 543–553, 2009