Rate coefficients for the reaction of the acetyl radical, CH<inf>3</inf>CO, with Cl<inf>2</inf> between 253 and 384 K

Rate coefficients, k, for the gas-phase reaction CH3CO + Cl 2 → 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 pulsedlaser 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 aweak negative temperature dependence that iswell 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 CH 3CO + Cl2 reaction is presented. * Int J Chem Kinet 41: 543-553, 2009 © 2009 Wiley Periodicals, Inc.