The specific features of the liquid-phase oxidation of saturated esters. Kinetics, reactivity and mechanisms of formation of destruction products

Abstract

Data on kinetics, reactivity, and mechanisms of formation of destruction products of the liquid-phase oxidation of saturated esters by molecular oxygen have been systematized and discussed. The ester group has both an activating and deactivating eff ects on the reactivity of the СН bonds of the alkoxyl (α´-, β´-, γ´-, and δ´-) and acyl (α-, β-, and γ-) groups. The activating eff ect in esters is weaker than in alcohols, ketones, and ethers and extends to the αand α´-CH bonds. The reactivity of the β-, β´-, and γ´-СН bonds is signifi cantly lower than that of the secondary СН bonds of hydrocarbons. Oxidation of the β-СН bonds of the acyl moieties of esters leads to НОО • radical, α,β-epoxy-, α,β-dihydroxy-, and α,β-unsaturated esters, but not to hydroperoxides. Upon the oxidation of esters, the highly active α-carboxyalkylperoxy-, α-acyloxyperoxy-, and НОО • -radicals are formed. The recombination reactions involving these radicals occur both with and without chain termination. The specifi city of the decomposition of ester hydroperoxides are due to intra-and intermolecular interactions of the hydroperoxide groups with the ester groups. Labile peroxide intermediates (α-hydroxyperoxyesters, peroxyesters, and peroxylactones) are formed through the corresponding tetrahedral intermediates and decay predominantly by the non-radical pathway. The recombination of the peroxyl radicals and the decay of labile peroxides result in the parallel accumulation of per oxide and non-peroxide products during the oxidation of esters.

Photooxidation-Initiated Aqueous-Phase Formation of Organic Peroxides: Delving into Formation Mechanisms

“…The lifetime of RO 2 radicals can be very difficult to gauge as they undergo multiple reaction pathways. , Despite the complexity associated with RO 2 radicals, ,, we believe that the decreasing trend in the γ of m / z 223 (Figure D) can be attributed to pathway 1d in Scheme . It is our understanding that, at enhanced precursor concentrations, the RO 2 radicals can form unstable oxygenated intermediates (e.g., tetroxides), , which are highly likely to decompose to alcohols and carbonyls. While additional decomposition products such as ROOR can be expected, it would be possible at even higher precursor concentrations (>10 mM), which are irrelevant to cloud water conditions.…”

“…72,99 Despite the complexity associated with RO 2 radicals, 1,96,99 we believe that the decreasing trend in the γ of m/z 223 (Figure 4D) can be attributed to pathway 1d in Scheme 1. It is our understanding that, at enhanced precursor concentrations, the RO 2 radicals can form unstable oxygenated intermediates (e.g., tetroxides), 72,99 which are highly likely to decompose to alcohols and carbonyls. While additional decomposition products such as ROOR can be expected, 1 it would be possible at even higher precursor concentrations (>10 mM), which are irrelevant to Based on the above observations, we hypothesize that the γ of aqueous ROOHs can be suppressed by increasing oxidant and precursor concentrations.…”

Aqueous-phase autoxidation in the atmosphere: fate and formation of organic peroxides

“…The lifetime of RO 2 radicals can be very difficult to gauge due to undergoing multiple reaction pathways. 58,82 Despite the complexity associated with RO 2 radicals, 79,82,83 we believe that the decreasing trend in the γ of m/z 223 (Figure 4 (C)) can be attributed to pathway 1d in Scheme 1. It is our understanding that at enhanced precursor concentrations, the RO 2 radicals can form unstable oxygenated intermediates (e.g., tetroxides), 58,82 which are highly likely to decompose to alcohols and carbonyls.…”

“…58,82 Despite the complexity associated with RO 2 radicals, 79,82,83 we believe that the decreasing trend in the γ of m/z 223 (Figure 4 (C)) can be attributed to pathway 1d in Scheme 1. It is our understanding that at enhanced precursor concentrations, the RO 2 radicals can form unstable oxygenated intermediates (e.g., tetroxides), 58,82 which are highly likely to decompose to alcohols and carbonyls. While additional decomposition products such as ROOR can be expected, 83 it would be possible at even higher precursor concentrations (>10 mM), which are currently beyond the scope of this study.…”