UV absorption spectra of HO₂, CH₃O₂, C₂H₅O₂, and CH₃C(O)CH₂O₂ radicals and mechanism of the reactions of F and Cl atoms with CH₃C(O)CH₃

Abstract

Pulse radiolysis techniques were used to measure the gas phase UV absorption spectra of the title peroxy radicals over the range 215-340 nm. By scaling to σ(CH 3 O 2 ) 240 nm = (4.24 ± 0.27) × 10 −18 , the following absorption cross sections were determined: σ(HO 2 ) 240 nm = 1.29 ± 0.16, σ(C 2 H 5 O 2 ) 240 nm = 4.71 ± 0.45, σ(CH 3 C(O)CH 2 O 2 ) 240 nm = 2.03 ± 0.22, σ(CH 3 C(O)CH 2 O 2 ) 230 nm = 2.94 ± 0.29, and σ(CH 3 C(O)CH 2 O 2 ) 310 nm = 1.31 ± 0.15 (base e, units of 10 −18 cm 2 molecule −1 ). To support the UV measurements, F TIR-smog chamber techniques were employed to investigate the reaction of F and Cl atoms with acetone. The F atom reaction proceeds via two channels: the major channel (92% ± 3%) gives CH 3 C(O)CH 2 radicals and HF, while the minor channel (8% ± 1%) gives CH 3 radicals and CH 3 C(O)F. The majority (>97%) of the Cl atom reaction proceeds via H atom abstraction to give CH 3 C(O)CH 2 radicals. The results are discussed with respect to the literature data concerning the UV absorption spectra of CH 3 C(O)CH 2 O 2 and other peroxy radicals.

Temperature‐dependent kinetics study of the gas‐phase reactions of atomic chlorine with acetone, 2‐butanone, and 3‐pentanone

“…Although direct observation of reaction products is not possible in our study, the independence of measured rate coefficients to significant variation in pressure is consistent with the expectation that all three reactions proceed predominantly via a hydrogen transfer mechanism. Several product analysis studies reported in the literature 23,41,42 confirm that H‐transfer is the dominant pathway for Cl reactions with ketones. It should be noted that the reactivity of ketones toward Cl atom observed in this study increases as the number of secondary H atoms in the ketone reactant increases.…”

Acetonyl Peroxy and Hydro Peroxy Self- and Cross-Reactions: Kinetics, Mechanism, and Chaperone Enhancement from the Perspective of the Hydroxyl Radical Product

“…21,26,29,36 The reported uncertainties were calculated through propagation of error and include the uncertainty in the linear fit, the pathlength, and the determined initial concentrations. 21 Cox et al (squares), 26 Nielsen et al (´), 29 Figure 5 shows comparisons between experimental data and the kinetic model using the IUPAC 66 recommended value of k2, 8.0 × 10 -12 cm 3 molecule -1 s -1 , vs. the value for k2 determined from our MC simulations, 4.8 × 10 -12 cm 3 molecule -1 s -1 . As is clearly seen, the recommended value for k2 does not capture the CH3C(O)CH2O2 kinetics observed in our experiments.…”

UV absorption spectra and self‐reaction rate constants for primary peroxy radicals arising from the chlorine‐initiated oxidation of carbonyl compounds

“…Assuming that the UV absorption spectrum of the (CH 3 ) 3 CC(O)CH 2 O 2 . radical was similar to that of the acetonylperoxy radical [13,14] (see section 3.3), the UV absorption spectrum of the (CH 3 ) 2 (CH 2 O 2 . )CC(O)CH 3 radical was determined and is presented in Fig.…”

“…radical because values of UV absorption cross-sections determined by Nielsen et al [14] did not allow us to adequately simulate experimental curves. Combining the uncertainties described above, we estimate a global systematic uncertainty of 22% in the absorption cross-section of the (CH 3 ) 2 (CH 2 O 2 .…”

“…× 10 6d [23] 32 14 . Allowing for an uncertainty of 30% in the absorption cross-section of (CH 3 ) 2 CO 2 .C(O)CH 3 and in the branching ratio of the reaction (14) (␣ 14 = k 14a /k 14 ) result, respectively, in an uncertainty of 28% and 26% in the value of k 14 .…”