Temperature‐dependent rate coefficients and mechanism for the gas‐phase reaction of chlorine atoms with acetone

Abstract

AbstractThe rate coefficient for the gas‐phase reaction of chlorine atoms with acetone was determined as a function of temperature (273–363 K) and pressure (0.002–700 Torr) using complementary absolute and relative rate methods. Absolute rate measurements were performed at the low‐pressure regime (∼2 mTorr), employing the very low pressure reactor coupled with quadrupole mass spectrometry (VLPR/QMS) technique. The absolute rate coefficient was given by the Arrhenius expression k(T) = (1.68 ± 0.27) × 10−11 exp[−(608 ± 16)/T] cm3 molecule−1 s−1 and k(298 K) = (2.17 ± 0.19) × 10−12 cm3 molecule−1 s−1. The quoted uncertainties are the 2σ (95% level of confidence), including estimated systematic uncertainties. The hydrogen abstraction pathway leading to HCl was the predominant pathway, whereas the reaction channel of acetyl chloride formation (CH3C(O)Cl) was determined to be less than 0.1%. In addition, relative rate measurements were performed by employing a static thermostated photochemical reactor coupled with FTIR spectroscopy (TPCR/FTIR) technique. The reactions of Cl atoms with CHF2CH2OH (3) and ClCH2CH2Cl (4) were used as reference reactions with k3(T) = (2.61 ± 0.49) × 10−11 exp[−(662 ± 60)/T] and k4(T) = (4.93 ± 0.96) × 10−11 exp[−(1087 ± 68)/T] cm3 molecule−1 s−1, respectively. The relative rate coefficients were independent of pressure over the range 30–700 Torr, and the temperature dependence was given by the expression k(T) = (3.43 ± 0.75) × 10−11 exp[−(830 ± 68)/T] cm3 molecule−1 s−1 and k(298 K) = (2.18 ± 0.03) × 10−12 cm3 molecule−1 s−1. The quoted errors limits (2σ) are at the 95% level of confidence and do not include systematic uncertainties. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 724–734, 2010