Kinetics and Mechanisms for the Reactions of Phenyl Radical with Ketene and its Deuterated Isotopomer: An Experimental and Theoretical Study

Abstract

Kinetics and mechanism for the reaction of phenyl radical (C6H5) with ketene (H2C beta=C alpha=O) were studied by the cavity ring-down spectrometric (CRDS) technique and hybrid DFT and ab initio molecular orbital calculations. The C6H5 transition at 504.8 nm was used to detect the consumption of the phenyl radical in the reaction. The absolute overall rate constants measured, including those for the reaction with CD2CO, can be expressed by the Arrhenius equation k = (5.9 +/- 1.8) x 10(11) exp[-(1160 +/- 100)/T] cm3 mol-1 s-1 over a temperature range of 301-474 K. The absence of a kinetic isotope effect suggests that direct hydrogen abstraction forming benzene and ketenyl radical is kinetically less favorable, in good agreement with the results of quantum chemical calculations at the G2MS//B3LYP6-31G(d) level of theory for all accessible product channels, including the above abstraction and additions to the C alpha, C beta, and O sites. For application to combustion, the rate constants were extrapolated over the temperature range of 298-2500 K under atmospheric pressure by using the predicted transition-state parameters and the adjusted entrance reaction barriers E alpha = E beta = 1.2 kcal mol-1; they can be represented by the following expression in units of cm3 mol-1 s-1: k alpha = 6.2 x 10(19)T-23 exp[-7590/T] and k beta = 3.2 x 10(4)T2.4 exp[-246/T].

Methyl Vinyl Ketone+OH and Methacrolein+OH Oxidation Reactions: A Master Equation Analysis of the Pressure‐ and Temperature‐Dependent Rate Constants

“…Furthermore, the vertical shift of barrier heights to obtain consistent results is a common practice, www.chemeurj.org and is necessary especially if we want to build up realistic kinetic models that include effects such as pressure dependence. [50][51][52] The good agreement between our results and the experimental data validates this small lowering of energy.…”

Preparation of the Cyclopentazole Anion in the Bulk: A Computational Study

“…Lin’s group reported rate constants for many phenyl radical reactions with several reactants. , O 2 reacts rapidly to convert phenyl to C 6 H 5 O 2 ; at 296 K, the rate constant of the reaction is 1.4 × 10 –11 cm 3 molecule –1 s –1 = 8.4 × 10 9 lit mol –1 s –1 . , The reaction rate constant is almost independent of pressure of O 2 . The peroxyphenyl radical, which is rather inert, absorbs at 496.4 nm.…”

Trigonal Bipyramidal Rhodium(I) Methyl and Phenyl Complexes: Precursors of Oxidative Methyl and Phenyl Radical Generation

“…Therefore, it has been thoroughly characterised by UV, [15] IR, [16] and Raman spectroscopy [17]. The kinetics of its reactivity with various reagents (e.g., propene, [18] ketene, [19] methylacetylene, [20] or n-Bu 3 SnH [21]) have been extensively studied. Various precursors can be chosen in order to obtain phenyl radicals such as benzoyl peroxides, [22][23][24][25] benzoic anhydride, [26] halogenobenzenes, [27] and nitrosobenzene [28,29].…”