The gas phase reactions of benzyl radicals with O, O₃, and NO₃: Rate, mechanism, and unimolecular decomposition of the chemically activated benzoxy radical

Abstract

The reactions of the benzyl radical with O, O3, and NO3 are investigated in a discharge flow‐reactor with mass spectrometric detection. For the rate coefficients of the latter two reactions, we obtain values of 2.8·1013 and 1.93·1012 cm3 mol−1s−1, respectively (T≈300 K, P ≈ 2 mbar). The main products for all three reactions are C6H6 and C6H5CHO with relative yields of 0.60/0.40 (M. Bartels, J. Edelbüttel‐Einhaus, and K. Hoyermann, 22nd Int. Symp. on Combustion, p. 1041, The Combustion Institute. Pittsburgh 1988), 0.37/0.66, and 0.23/0.77, respectively. These branching fractions are interpreted in terms of the unimolecular decomposition of an intermediarily formed benzoxy radical, using statistical rate theory. The molecular data needed are calculated by quantum chemical methods. The verification of the experimental branching fractions requires the assumption of a direct reaction channel leading from C6H5CH2O to C6H6. The nature of this channel is still uncertain.

Reactions of C2H5Radicals with O, O3, and NO3: Decomposition Pathways of the Intermediate C2H5O Radical

“…It was carefully degassed before use. The NO 3 radicals are generated, , free of NO 2 , by the reaction of F atoms (inlet b 1 ) with HNO 3 admixed via inlet b 2 .…”

“…Here, we take into account all internal and external rotational degrees of freedom of C 2 H 5 and XO. Presumably, the decomposition of C 2 H 5 XO* proceeds statistically; the resulting distribution of C 2 H 5 O* for a well-defined disposable energy E′ in C 2 H 5 XO* is 5,6,19,22 where F and W denote the density and sum of states, respectively, for the corresponding fragment, C 2 H 5 O or X. Finally, by allowing E′ to be distributed according to eq 11, the combination of eqs 11 and 14 leads to where the sums of states in F′ have to be altered as mentioned above and…”

“…A further support for this hypothesis, at least for the reaction C 2 H 5 + NO 3 , comes from a recent work of Biggs et al, 4 who directly detected C 2 H 5 O radicals in this system by laser-induced fluorescence. In an analogous way, we already interpreted the unimolecular reactions of differently generated benzoxy radicals, 5 and a similar approach was also used to describe the kinetic behavior of certain oxy radicals under atmospheric conditions. 6,7 Thus, the present study has two objectives, which are interconnected.…”

Oxidation of the Benzyl Radical: Mechanism, Thermochemistry, and Kinetics for the Reactions of Benzyl Hydroperoxide

“…It is well-known that the initial stages of toluene oxidation predominantly result in the formation of the benzyl radical . The benzyl radical is thermally stable, and at low to moderate temperatures it is removed from combustion systems by oxidation reactions with species such as O 2 , OH, O, and HO 2 . Benzyl associates with O 2 to form the benzylperoxy radical in a mildly exothermic reaction (ca.…”

C3-selective C–H thiolation of quinolines via an N-arylmethyl activation strategy

“…Alternatively, the radical cation I undergoes homolytic cleavage of the N–C bond, followed by deprotonation to furnish the desired product with concomitant expulsion of naphthyl radical IV , which was evidenced by the detection of naphthaldehyde, 1-methylnaphthalene, and 1-(chloromethyl)naphthalene by GCMS analysis of the reaction mixture. 24…”