The kinetic regularities, products, and mechanism of the thermal decomposition of dimethyldioxirane. The contribution of molecular and radical reaction channels

Хурсан, С. Л.; Grabovskii, S. A.; Kabal'nova, N. N.; Galkin, E. G.; Шерешовец, В. В.

doi:10.1007/bf02495074

Cited by 7 publications

(5 citation statements)

References 31 publications

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“…12 The resulting k d value is in good accord with the thermolysis constant of dioxirane in acetone. 12 The rate constant k app is independent of the oxygen content in the reaction mixture and DMDO concentra tion. The kinetic equation of the reaction has the follow ing form:…”

Section: Resultssupporting

confidence: 69%

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Oxidation of ethers with dimethyldioxirane

2005

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Oxidation of a series of tert butyl ethers Bu t OR (R = Me, Et, CH 2 CH 2 Cl, Pr i , Bu i ), diethyl ether, diisopropyl ether, 1,2 dimethoxyethane, diisobutoxymethane, 1,4 dioxane, and tetra hydrofuran with dimethyldioxirane (DMDO) was studied. The reaction kinetics obeys the second order equation w = k[DMDO] [ether]. The rate constants in a range of 5-50 °C and the activation parameters of the reaction were determined. The solvent effect on the oxidation rate was studied. The oxidation products are the corresponding alcohols and carbonyl com pounds. The competition between the nonradical (oxygen insertion) and radical mechanisms of the reaction is discussed. The reactions of the parent dioxirane and DMDO with a series of methyl ethers MeOR´ (R´ = Me, Et, CH 2 CH 2 F, Pr i ) were studied by the density functional theory (DFT). The (U)B3LYP 6 311G(d,p) method was employed to calculate the geometry and energies of the reactants and transition states. The data obtained indicate a possible increase in the probability of oxidation via the radical route and an increase in the activation barrier for the substrates containing electron withdrawing substituents.The chemistry of dioxiranes was under intense devel opment for the last two decades. 1,2 A distinctive feature of these cyclic peroxides is a combination of high reactivity and selectivity of oxidation reactions. 3 The works con cerning the oxidation of ethers with dioxiranes are few and, as rule, synthetic. For instance, the transformation of steroid ethers to the corresponding ketones was stud ied. 4 The oxidation of O isopropylidene diol derivatives to 2 hydroxyketones and the oxidation of benzyl ethers were studied, 5,6 and a nonradical nature was postulated for these reactions. The oxidation of 1,3 dihydroiso benzofuran with dimethyldioxirane (DMDO) to 2 hydr oxymethylbenzaldehyde was assumed 7 to involve radi cals; however, the total composition of the products was not reported. The study 8 of the reaction products of dialkyl ethers with dioxiranes suggested the radical nature of this reaction, which has been developed further. 9,10 The study 10 of the products and kinetics of oxidation of ethers with DMDO concluded the competition of two processes: insertion of the oxygen atom at the C-H bond of the substrate and hydrogen atom abstraction followed by fast recombination of the radical pair that formed. The effect of oxygen on the yield of the products and conversion of the substrate were demonstrated for para substituted ana logs of 1 methoxy 1 phenylethane. Analysis of the ki netic data in the framework of the Hammett equation gives ρ = -0.74±0.03 (25 °C). 10 However, the mecha nism of oxidation of different ethers was not studied sys tematically. We have previously 11,12 shown that C-H bonds of alkanes and alcohols are oxidized with DMDO via two parallel channels, nonradical and homolytic. The ratio of these processes was determined. In the present work, we studied the products and kinetics of the reac tions of DMDO with aliphatic ethers 1-12 and the influ e...

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Section: Resultssupporting

confidence: 69%

“…10 However, the mecha nism of oxidation of different ethers was not studied sys tematically. We have previously 11, 12 shown that C-H bonds of alkanes and alcohols are oxidized with DMDO via two parallel channels, nonradical and homolytic. The ratio of these processes was determined.…”

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confidence: 99%

Oxidation of ethers with dimethyldioxirane

2005

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“…Compound 1 can be oxidized via both the mechanism of oxygen atom insertion (without par ticipation of radicals) and involving free radicals, as has been earlier found for dimethyldioxirane. 4 The latter re action pathway can result in the initiated oxidation of the solvent with oxygen. 26 After EMD decomposition, 3 hydroperoxybutan 2 one was found in oxygen saturated solutions of compound 1 along with the products pre sented in Table 1.…”

Section: Resultsmentioning

confidence: 99%

“…The bimolecular process is the reaction of sol vent oxidation with dioxirane that can proceed in two parallel routes. 4 The first route leads to nonradical prod ucts, and the second route affords a radical pair in the solvent cage. This assumption is confirmed by the results of high level quantum chemical calculations.…”

Section: Reaction Mechanismmentioning

confidence: 99%

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Products, kinetic regularities, and mechanism of thermal decomposition of ethyl(methyl)dioxirane

et al. 2006

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The products and kinetic regularities of thermal decomposition of ethyl(methyl)dioxirane (EMD) were studied. The consumption of EMD occurs via four parallel pathways: two isomer izations to ethyl acetate and methyl propionate, solvent oxidation via insertion of the oxygen atom into the C-H bond of a solvent molecule (butanone), and hydrogen atom abstraction from the solvent by dioxirane with radical escape from the cage. The contribution of the latter route to the oxidation of butan 2 one at 35 °C is 43%. Alkyl radicals initiate EMD decomposi tion in an inert atmosphere. The activation parameters of EMD isomerization to esters and the reaction of EMD with butanone were determined. The isomerization of EMD was studied by the DFT method. The geometric parameters were optimized at the UB3LYP level using the 6 31G** and/or 6 311+G** basis sets. The calculated energies were corrected taking into account zero point vibrations. The theoretical results are in good agreement with experimental data. The mechanism of EMD thermolysis is considered.

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Organic tetroxides and mechanism of peroxy radical recombination

Khursan

2014

Patai's Chemistry of Functional Groups

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The chemical properties of organic tetroxides, that is, compounds of a general formula ROOOOR (R = H or organic radical) are discussed. The following tetroxides are considered: hydrogen tetroxide HOOOOH, dialkyl tetroxides ROOOOR, hydrotetroxides ROOOOH, and five‐membered cyclic tetroxides—tetroxolanes. Hydrogen tetroxide is formed via self‐reaction of HOO · radicals on singlet PES; hydroperoxy radical interaction plays an important role in the chemistry of atmosphere. The formation and subsequent decay of tetroxides are discussed in detail. Similar self‐reaction of alkylperoxy radicals leads to organic tetroxides. Its irreversible transformation occurs in two directions depending on the tetroxide structure: the facile homolysis of ROOOOR bond or the induced by αCH bond radical decomposition of tetroxide into hydroperoxy, alkoxy radicals, and carbonyl compound. The latter interaction is the key step in the new mechanism of peroxy radical recombination suggested on the base of extensive analysis of available literature. Hydrotetroxides show properties similar to both HOOOOH and dialkyl tetroxides. A possibility of tetroxolane generation in the reaction of ozone with carbonyl compounds is discussed.

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The kinetic regularities, products, and mechanism of the thermal decomposition of dimethyldioxirane. The contribution of molecular and radical reaction channels

Cited by 7 publications

References 31 publications

Oxidation of ethers with dimethyldioxirane

Oxidation of ethers with dimethyldioxirane

Products, kinetic regularities, and mechanism of thermal decomposition of ethyl(methyl)dioxirane

Organic tetroxides and mechanism of peroxy radical recombination

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