The rate coefficient for the gas-phase reaction of Cl atoms with ethyl formate was measured over the temperature range of 268-343 K using relative rate methods, with ethyl chloride as a reference compound. The temperature dependent relative rate coefficients for the ethyl formate + Cl reaction were measured, and the modified Arrhenius expression kethyl formate(268-343) = (2.54 ± 0.57) × 10(-23) T(4.1) exp {-(981 ± 102)/T} cm(3) molecule(-1) s(-1) was obtained with 2σ error limits. The room temperature rate coefficient for the title reaction is (9.84 ± 0.79) × 10(-12) cm(3) molecule(-1) s(-1), which is in good agreement with reported values. To complement the experimental measurement, computational methods were used to calculate the rate coefficient for the ethyl formate + Cl reaction atoms using canonical variational transition state theory (CVT) with small curvature tunneling (SCT) and the CCSD (T)/cc-pVDZ//M062X/6-31+g(d,p) level of theory. The temperature dependent Arrhenius expression was obtained to be 2.97 × 10(-18) T(2.4) exp[-(390/T)] cm(3) molecule(-1) s(-1) over the temperature range of 200-400 K. The thermodynamic parameters and branching ratio were calculated. Also, the atmospheric lifetime and global warming potentials (GWPs) were calculated for ethyl formate.
Rate coefficients, k, for the gas-phase reaction CH 3 CO + 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 CH 3 CO with CH 3 CO produced by the 248-nm pulsedlaser photolysis of acetone, CH 3 C(O)CH 3 , or 2,3-butadione, CH 3 C(O)C(O)CH 3 . The loss of CH 3 CO was monitored by cavity ring-down spectroscopy (CRDS) at 532 nm. Rate coefficients were determined by first-order kinetic analysis of the CH 3 CO temporal profiles for [Cl 2 ] < 1 × 10 14 molecule cm −3 and the analysis of the CRDS profiles by the simultaneous kinetics and ring-down method for experiments performed with [Cl 2 ] > 1 × 10 14 molecule cm −3 . k 2 (T ) was found to be independent of pressure, with k 2 (296 K) = (3.0 ± 0.5) × 10 −11 cm 3 molecule −1 s −1 . k 2 (T ) showed a weak negative temperature dependence that is well reproduced by the Arrhenius expression k 2 (T ) = (2.2 ± 0.8) × 10 −11 exp[(85 ± 120)/T ] cm 3 molecule −1 s −1 . The quoted uncertainties in k 2 (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 3 CO + Cl 2 reaction is presented. C
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