̇QOOH-mediated reactions in cyclohexene oxidation

Isomer‐dependent reaction mechanisms of cyclic ether intermediates: cis‐2,3‐dimethyloxirane and trans‐2,3‐dimethyloxirane

“…Cyclic ethers are a class of metastable intermediates produced fromQOOH radicals in a chain-propagating step that continue to undergo chain reactions and may play integral roles in the overall reaction mechanism. [23][24][25] Concentrations of cyclic ethers provideQOOH-isomer-specific modeling targets and are commonly measured from steady-state experiments, 26,27 which reflect the balance between formation and consumption reactions. Because of the direct connection toQOOH radicals via chain propagation, a reasonable expectation is that uncertainty in the consumption mechanisms of cyclic ethers contributes directly to mechanism truncation error and is a source of uncertainty in predictions of autoignition and species profiles.…”

“…Cyclic ethers are a class of metastable intermediates produced from ̇QOOH radicals in a chain‐propagating step that continue to undergo chain reactions and may play integral roles in the overall reaction mechanism 23–25 . Concentrations of cyclic ethers provide ̇QOOH‐isomer‐specific modeling targets and are commonly measured from steady‐state experiments, 26,27 which reflect the balance between formation and consumption reactions.…”

Reaction mechanisms of a cyclic ether intermediate: Ethyloxirane

“…Other contributions to account for the ion signal at m/z 70 above 10 eV were also considered, and all are related to fragment cations of ketohydroperoxide‐type radicals, which are of nominal mass‐to‐charge ratio, m/z 103. Time‐dependent ion signal at m/z 103 was detected in the experiments, although signal‐to‐noise levels were low, likely due to low steady‐state concentrations since the molecular structures are analogous to other resonance‐stabilized ̇QOOH 1,13 . Dissociative ionization of the m/z 103 radicals, such as the two in Figure 13, yield m/z 70 cations upon loss of neutral m/z 33—the nominal mass of HOO.…”

“…Timedependent ion signal at m/z 103 was detected in the experiments, although signal-to-noise levels were low, likely due to low steady-state concentrations since the molecular structures are analogous to other resonance-stabilizeḋ QOOH. 1,13 Dissociative ionization of the m/z 103 radicals, such as the two in Figure 13, yield m/z 70 cations upon loss of neutral m/z 33-the nominal mass of HOO. Dissociation via loss of HOO is typical in hydroperoxides, including ketohydroperoxides 70 and others such as tertbutyl hydroperoxide (m/z 90), where a cation of m/z 57 is the most abundant peak in the mass spectrum (Supplemental Material S17).…”

“…Low-temperature combustion of hydrocarbons involves the formation of hydroperoxy-substituted carbon-centered radicals (QOOH), the subsequent reactions of which yield functionalized metastable intermediates that continue to undergo oxidation and may play integral roles in the broader picture of oxidation. 1,2 In the forward direction, two consumption pathways compete foṙ QOOH: bimolecular reaction with O 2 , forming the adducṫ OOQOOH, and unimolecular decomposition. The latter produces an abundance of isomers either through chainpropagating or chain-inhibiting steps.…”