Kinetic Investigations of the Reaction of Phenyl Radicals with Ethyl Acetate in the Gas Phase: An Experimental and Computational Study

Cavity ring-down spectroscopy (CRDS) was employed to investigate the kinetics of the reaction between phenyl radicals (C₆H₅^•) and ethyl acetate (EtOAc) in the gas phase. Nitrosobenzene (C₆H₅NO) was used as the radical precursor to generate C₆H₅^• at 248 nm, and the generated radicals were subsequently probed at 504.8 nm. The rate coefficients were investigated experimentally in the temperature range of 258-358 K with an interval of 20 K and at a total pressure of 55 Torr in the nitrogen atmosphere. The obtained Arrhenius expression for the title reaction (C₆H₅^• + EtOAc) in the temperature range of 258-358 K was k_{phenyl + EtOAc}^{Expt - (258 - 358 K)} = (9.33 ± 0.11) × 10^-16 exp[(883.7 ± 181.0)/T] cm³ molecule^-1 s^-1, and the rate coefficient at room temperature (298 K) was k_{phenyl + EtOAc}^{Expt - 298 K} = (2.20 ± 0.12) × 10^-14 cm³ molecule^-1 s^-1. Negligible effects of pressure and photolysis laser fluence were found on the experimentally measured rate coefficients. To complement our experimental findings, rate coefficients of the title reaction were computationally investigated employing the canonical variational transition-state theory with small curvature tunnelling (CVT/SCT) at the CCSD(T)/cc-pVDZ//B3LYP/6-31+G(d,p) level of theory in the temperature range of 200-400 K. The temperature-dependent rate coefficient in the studied temperature range was obtained to be k_{phenyl + EtOAc}^{Theory - (200 - 400 K)} = (7.68 ± 0.12) × 10^-17 exp[(1731.6 ± 216.0)/T] cm³ molecule^-1 s^-1, and the rate coefficient at 298 K was obtained as k_{phenyl + EtOAc}^{Theory - 298 K} = 2.45 × 10^-14 cm³ molecule^-1 s^-1. Both the experimentally measured and computed rate coefficients show good agreement at 298 K. A negative temperature dependency was observed for both the experimentally measured and computed rate coefficients. A detailed discussion of the thermochemical parameters and branching ratios of the title reaction are also presented in this Article.