Thermal stability of carbonyl radicals Part I. Straight-chain and branched C4 and C5 acyl radicals

Measurement-model comparison of stabilized Criegee Intermediate and Highly Oxygenated Molecule production in the CLOUD chamber

“…The selected dimer (C19H28O11) formation starts clearly later, which supports the hypothesis that it forms from reaction of two RO2 Jokinen et al, 2014). The carbon number 19 can be explained by loss of CO from RO2 (Jagiella et al, 2000;Rissanen et al, 2014), followed by reaction with a 10- …”

Falloff curves for the unimolecular decomposition of two acyl radicals: RCO (+M) → R + CO (+M) by pulsed laser photolysis coupled to time‐resolved infrared diode laser absorption

“…Though the direct monitoring of the build up of [CO] is obviously more direct than the methodologies employed by the two previous groups [3,4], it has an essential drawback in that it is difficult to separate CO generated from the initial fast decomposition (RCO → R + CO) from the subsequent slower generation of additional CO due to the chain reactions triggered by Cl 2 (RCO or R − −−→ based on numerical simulations of a complex chemical mechanism including the chain reactions, because the rate constants of the chain reactions are not very well known. We thus have overcome the drawback of the chain reactions by adding a radical scavenger: O 2 ; in these conditions, the consumption of RCO, and thus also the buildup of CO, is now mainly governed by the total rate constant…”

“…• Jagiella et al [3] have used a photoreactor coupled to FTIR spectroscopy. [4] have combined their experimental results with ab initio and statistical (RRKM) studies and to estimate the variation of k d over a large pressure range for both pivaloyl and isobutyryl radicals.…”

“…Theoretical calculations [2] and the few experiments of Jagiella et al [3] show that the barrier for decomposition of RCO is much lower for large acyl radicalswith R containing at least four carbon atoms-than for acetyl or propionyl. For such acyl radicals, the unimolecular decomposition…”

“…Our values of k d , which are in the falloff range, are compared to those obtained from theoretical calculations using the Troe formalism [5]. For pivaloyl at 298 K, we obtain the following limiting rate constants : k 0 = 2.1 × 10 −13 cm 3 The main atmospheric sinks of these peroxyacyl radicals are reaction with NO 2 forming PAN (peroxy acetyl nitrate) type compound such as RC(O)OONO 2 , reaction with NO: (RC(O)OO + NO → R + CO 2 + NO 2 ) or reaction with other peroxy radicals (HO 2 , RO 2 , RC(O)O 2 ) [1]. Acyl radicals thus play an important role in the chemical mechanisms of tropospheric chemistry since they influence the budgets of HO 2 /RO 2 radicals and of NO x .…”