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Kinetic Investigations of the Reaction of Phenyl Radicals with Ethyl Acetate in the Gas Phase: An Experimental and Computational Study
journal contribution
posted on 2020-06-30, 11:35 authored by Koushik Mondal, B. RajakumarCavity
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 kphenyl + EtOAcExpt – (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 kphenyl + EtOAcExpt – 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 kphenyl + EtOAcTheory – (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 kphenyl + EtOAcTheory – 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.