Mechanism of Thermal Toluene Autoxidation

Hermans, Ive; Peeters, Jozef; Vereecken, Luc; Jacobs, Pierre

doi:10.1002/cphc.200700563

Cited by 67 publications

(130 citation statements)

References 24 publications

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“…The efficiency of the reaction depends on the stability of the alkyl radical: the more stable the radical, the lower its reactivity and the lower the efficiency of the cage reaction. This efficiency has been experimentally measured for the three different hydrocarbon substrates: cyclohexane, [6,8] toluene, [11] and ethylbenzene, [7] as 70, 55, and 20 %, respectively, and is in line with expectations. For the case of the cyclohexane oxidation, the alkoxyl radicals co-produced in Equation (7) are partially converted to additional alcohol upon reaction with the substrate [Equation (2)], and also partially isomerized into wformyl radicals [Equation (8)].…”

Section: Introductionsupporting

confidence: 87%

“…[11] This analysis was performed for the most important products; the results are shown in Figure 5.…”

Section: Primary or Secondary Nature Of The Reaction Productsmentioning

confidence: 99%

“…This means that 11 % of the caged {Q=O+ROOH+R · +H 2 O} products will undergo the activated cage-reaction shown in Scheme 7. As a comparison, this cage-fraction was measured to be 0.7, 0.55, and 0.2 for cyclohexane, [6][7][8] toluene, [11] and ethylbenzene, [7] respectively. It should thus be emphasized that the obtained value for f of approximately 0.11 is fully in line with the cage-efficiencies determined before for other substrates.…”

Section: The Origin Of Alcohol and Ketonementioning

confidence: 99%

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Mechanism of the Aerobic Oxidation of α‐Pinene

2010

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A combined experimental and theoretical approach is used to study the thermal autoxidation of α‐pinene. Four different types of peroxyl radicals are generated; the verbenyl peroxyl radical being the most abundant one. The peroxyl radicals propagate a long radical chain, implying that chain termination does not play an important role in the production of the products. Two distinct types of propagation steps are active in parallel: the abstraction of allylic H atoms and the addition to the unsaturated CC bond. The efficiency for both pathways appears to depend on the structure of the peroxyl radical. The latter step yields the corresponding epoxide product, as well as alkoxyl radicals. Under the investigated reaction conditions the alkoxyl radicals seem to produce both the alcohol and ketone products, the ketone presumably being formed upon the abstraction of the weakly bonded αH atom by O2. This mechanism explains the predominantly primary nature of all quantified products. At higher conversion, co‐oxidation of the hydroperoxide products constitutes an additional, albeit small, source of alcohol and ketone products.

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Section: Introductionsupporting

confidence: 87%

“…[11] This analysis was performed for the most important products; the results are shown in Figure 5.…”

Section: Primary or Secondary Nature Of The Reaction Productsmentioning

confidence: 99%

Section: The Origin Of Alcohol and Ketonementioning

confidence: 99%

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Mechanism of the Aerobic Oxidation of α‐Pinene

2010

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“…Taking into account this effect, it was possible to postulate that in the case of hydrocarbon autoxidation, not only the ketone can be obtained before the termination step, but also the alcohol. 165 | 166 (as a consequence of the ROOH generation in eq. 5 and eq.…”

Section: Solvent Cagesmentioning

confidence: 99%

“…202 In contrast the use of metal nanoparticle based systems like Au/MgO or Au/ZSM-5 in liquid phase, showed an enhancement of the autoxidation pathway only, thus suggesting that the metal in this case is actually a promoter. 148,154 To date one of the most complete schemes in the propagation reaction of the alkyl peroxide radical is the one obtained by Jacobs and coworkers (Scheme 9) It also considers the formation of ring opening products like formyl species 165 thus showing the variety of combinations that reactions just involving ground state triplet oxygen can achieve when compared to pure catalytic processes involving heterolytic oxygen activation. Scheme 9.…”

Section: Cyclohexane Oxidation: An Exploited Case Of Autoxidationmentioning

confidence: 99%

Catalytic oxygen activation versus autoxidation for industrial applications: a physicochemical approach

Liu

Ryabenkova

Conte

2015

Phys. Chem. Chem. Phys.

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The activation and use of oxygen for the oxidation and functionalization of organic substrates is among the most important reactions in a chemist's toolbox. Nevertheless, despite the vast literature on catalytic oxidation, the phenomenon of autoxidation, an ever-present background reaction that occurs in virtually every oxidation process, is often neglected. In contrast, autoxidation can affect the selectivity to a desired product, to those dictated by pure freeradical chain pathways, thus affecting the activity of any catalyst used to carry out a reaction.This critical review compares catalytic oxidation routes by transition metals versus autoxidation, particularly focusing on the industrial context, where highly selective and "green" processes are needed. Furthermore, the application of useful tests to discriminate between different oxygen activation routes, especially in the area of hydrocarbon oxidation, with the aim of an enhanced catalyst design, is described and discussed. In fact, one of the major targets of selective oxidation is the use of molecular oxygen as ultimate oxidant, combined with the development of catalysts capable to perform the catalytic cycle in a real energy and cost effective manner on a large scale. To achieve this goal, insights from metallo-proteins that could find application in some areas of industrial catalysis are presented, as well as considering the physicochemical principles that are at the fundament of oxidation and autoxidation processes.3

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Oxidation

Teles

Hermans

Franz³

et al. 2015

Ullmann's Encyclopedia of Industrial Chemistry

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The article contains sections titled: 1. Introduction 2. Overview of industrial oxidation processes 2.1. Inorganic chemicals 2.1.1. Sulfur derivatives 2.1.2. Carbon derivatives 2.1.3. Nitrogen derivatives 2.1.4. Chlorine derivatives 2.2. Organic chemicals 2.2.1. Olefins and alkynes 2.2.2. Epoxides 2.2.3. Hydroperoxides 2.2.4. Alcohols 2.2.5. Aldehydes 2.2.6. Ketones 2.2.7. Phenols and derivatives 2.2.8. Carboxylic acids, saturated 2.2.9. Carboxylic acids and anhydrides, unsaturated 2.2.10. Carboxylic acids and anhydrides, aromatic 2.2.11. Esters, lactones and carbonates 2.2.12. Nitriles 2.2.13. Oxidized nitrogen compounds 2.2.14. Chlorinated compounds 2.2.15. Sulfur compounds 3. Thermodynamics; Stability of Hydrocarbons 4. Reaction Types 5. Homolytic Oxidation 5.1. Historical Development; Reaction Mechanism; Radical Reactivity 5.2. Kinetics of Autoxidation 5.3. Differences between Liquid‐ and Gas‐Phase Autoxidations 5.4. Homolytic Oxidation in the Liquid Phase 5.4.1. Secondary Reactions of Radicals, Peroxides, and other Intermediates 5.4.2. Metal Catalysis in Homolytic Liquid‐Phase Oxidation 5.4.3. Inhibitors of Homolytic Liquid‐Phase Oxidation 5.4.4. Special Cases of Homolytic Oxidation 5.4.5. Process Technology of Homolytic Liquid‐Phase Oxidation 5.5. Homolytic Gas‐Phase Oxidation 5.6. Gas Explosions and Safety Data 6. Heterolytic Oxidation 6.1. Heterolytic Oxidation in the Liquid Phase 6.2. Heterogeneously Catalyzed Gas‐Phase Oxidation 6.2.1. Oxidation Catalysts 6.2.2. Process Technology of Heterogeneously Catalyzed Oxidations

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Mechanism of Thermal Toluene Autoxidation

Cited by 67 publications

References 24 publications

Mechanism of the Aerobic Oxidation of α‐Pinene

Mechanism of the Aerobic Oxidation of α‐Pinene

Catalytic oxygen activation versus autoxidation for industrial applications: a physicochemical approach

Oxidation

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