Gas Phase Kinetics of 2,2,2-Trifluoroethylbutyrate with the Cl Atom: An Experimental and Theoretical Study.

Abstract

The gas phase temperature dependent rate coefficients of Cl atoms with 2,2,2-trifluoroethylbutyrate, CH3CH2CH2C(O)OCH2CF3, were measured in the temperature range 268-343 K, at atmospheric pressures using the relative rate method, with ethyl acetate and ethane as reference compounds. The temperature dependent rate coefficients for the reaction of 2,2,2-TFEB + Cl were measured and were used to deduce the Arrhenius expression: k268-343K = [(4.42 ± 0.01) × 10(-19)]T(2.6) exp{(1132 ± 566)/T} cm(3) molecule(-1) s(-1). At 298 K, the rate coefficient for the title reaction is (4.54 ± 2.87) × 10(-11) cm(3) molecule(-1) s(-1), which is in good agreement with a previously reported value at 298 K. To complement our experimental results over the studied temperature range, theoretical kinetic calculations were also performed for the title reaction using canonical variational transition state theory (CVT) with small curvature tunneling (SCT) corrections in combination with the CCSD(T)/cc-pVDZ//M062X/6-31+g(d,p) level of theory. The temperature dependent Arrhenius expression was obtained to be k(T) = (1.89 ± 2.64) × 10(-21)T(3.4) exp{(1321 ± 111)/T} cm(3) molecule(-1) s(-1). The branching ratios, atmospheric implications, and degradation mechanism of 2,2,2-trifluoroethylbutyrate, CH3CH2CH2C(O)OCH2CF3, were discussed in detail in this manuscript.