THE INHIBITION OF AUTOXIDATION BY 2,4,6-TRI-<i>tert</i>-BUTYL SUBSTITUTED PHENOL, ANILINE, AND THIOPHENOL

Gardner, D. V.; Howard, J. A.; Ingold, K. U.

doi:10.1139/v64-421

Cited by 16 publications

(10 citation statements)

References 10 publications

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“…Aforementioned discussion proves that the main reactive radical accounting for SMX degradation in the Co/PAA process was R–O • rather than HO • . The detected hydroxyl-SMX derivative (TP-270) after reaction indicated hydroxylation reaction took place on the aniline ring, which would be explained by the formation of aniline radicals via hydrogen atom abstraction by peroxyl radicals (pathway I) . SMX can be also oxidized to nitroso-SMX (TP-268) which can be further converted to nitro-SMX, indicating that the −NH 2 group contained in SMX is vulnerable to R–O • in the Co/PAA process (pathway II).…”

Section: Resultsmentioning

confidence: 99%

“…The detected hydroxyl-SMX derivative (TP-270) after reaction indicated hydroxylation reaction took place on the aniline ring, which would be explained by the formation of aniline radicals via hydrogen atom abstraction by peroxyl radicals (pathway I). 68 SMX can be also oxidized to nitroso-SMX (TP-268) which can be further converted to nitro-SMX, indicating that the −NH 2 group contained in SMX is vulnerable to R−O • in the Co/PAA process (pathway II). Meanwhile, a number of dimeric products were identified, illustrating coupling reaction also occurred during the degradation of SMX in the Co/PAA process (pathway III).…”

Section: Environmental Science and Technologymentioning

confidence: 99%

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Application of Cobalt/Peracetic Acid to Degrade Sulfamethoxazole at Neutral Condition: Efficiency and Mechanisms

Wang

Xiong

et al. 2019

Environ. Sci. Technol.

367

193

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An advanced oxidation process of combining cobalt and peracetic acid (Co/PAA) was developed to degrade sulfamethoxazole (SMX) in this study. The formed acetylperoxy radical (CH3CO3 •) through the activation of PAA by Co (Co2+) was the dominant radical responsible for SMX degradation, and acetoxyl radical (CH3CO2 •) might also have played a role. The efficient redox cycle of Co3+/Co2+ allows good removal efficiency of SMX even at quite low dosage of Co (<1 μM). The presence of H2O2 in the Co/PAA process has a negative effect on the degradation of SMX due to the competition for reactive radicals. The SMX degradation in the Co/PAA process is pH dependent, and the optimum reaction pH is near-neutral. Humic acid and HCO3 – can inhibit SMX degradation in the Co/PAA process, while the presence of Cl– plays a little role in the degradation of SMX in this system. Although transformation products of SMX in the Co/PAA system show higher acute toxicity, the low Co dose and SMX concentration in aquatic solution can efficiently weaken the acute toxicity. After reaction in the Co/PAA process, numerous carbon sources that could be provided for bacteria and algae growth can be produced, suggesting that the proposed Co/PAA process has good potential when combined with the biotreatment processes.

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Section: Resultsmentioning

confidence: 99%

Section: Environmental Science and Technologymentioning

confidence: 99%

Application of Cobalt/Peracetic Acid to Degrade Sulfamethoxazole at Neutral Condition: Efficiency and Mechanisms

Wang

Xiong

et al. 2019

Environ. Sci. Technol.

367

193

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“…Although thiols have relatively weak S−H bonds (87 kcal/ mol) 4 and are highly useful HAT reagents in organic synthesis (mainly to reduce alkyl radicals, k = 1 × 10 7 M −1 s −1 ), 25 they are comparatively poor H-atom donors to peroxyl radicals, and the propensity of the product thiyl radicals to dimerize and react with O 2 generally limits the stoichiometry of their RTA reactions to (at most) a single peroxyl radical. 26 While studying the antioxidant mechanism of allicin, the characteristic odorous thiosulfinate from garlic (vide infra), we uncovered the impressive HAT chemistry of sulfenic acids (RSOH). Sulfenic acids arise from the two-electron oxidation of thiols, 27 which reduces the strength of the bond to the labile H-atom from ∼87 kcal/mol 4 to ∼70 kcal/mol 28,29 (Figure 5).…”

Section: ■ Organosulfur Antioxidantsmentioning

confidence: 99%

“…This is based on sulfur’s relatively high nucleophilicity and oxidizability to acids that are capable of dehydrating and/or cleaving peroxides in Hock-like processes. Although thiols have relatively weak S–H bonds (87 kcal/mol) and are highly useful HAT reagents in organic synthesis (mainly to reduce alkyl radicals, k = 1 × 10 7 M –1 s –1 ), they are comparatively poor H-atom donors to peroxyl radicals, and the propensity of the product thiyl radicals to dimerize and react with O 2 generally limits the stoichiometry of their RTA reactions to (at most) a single peroxyl radical …”

Section: Organosulfur Antioxidantsmentioning

confidence: 99%

Recent Insights on Hydrogen Atom Transfer in the Inhibition of Hydrocarbon Autoxidation

Poon

Pratt

2018

Acc. Chem. Res.

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Autoxidation, the free radical chain reaction that nominally inserts O into hydrocarbons to give peroxides, is primarily responsible for the degradation of all organic materials. Peroxyl radicals propagate autoxidation mainly by abstraction of labile H-atoms from the hydrocarbons, whereas radical-trapping antioxidants (RTAs) inhibit autoxidation by donating an H-atom to the peroxyl radical to give a nonpropagating radical. As such, a detailed understanding of the kinetics and thermodynamics of H-atom transfer (HAT) reactions to peroxyl radicals, and the effects of sterics, electronics, and medium thereupon, is key to understanding the mechanisms and products of autoxidation and the ability of RTAs to inhibit it. Due to their relatively weak O-H and N-H bonds, phenols and aromatic amines have long been utilized as RTAs, but only phenols have been extensively optimized to maximize their reactivity. Amines offer greater structural variability owing to their trivalent central nitrogen atom. Simply linking the two aromatic rings of a diarylamine to afford a phenoxazine offers profound differences in HAT reactivity: 1000-times greater than diphenylamine and 10-fold more reactive than α-tocopherol, Nature's optimized phenolic RTA. Thus, phenoxazines are an exciting scaffold for RTA development. Indeed, we have recently shown that ring substitution of phenoxazine or 2,4-diazaphenoxazine can yield compounds that undergo barrierless HAT reactions with peroxyl radicals. Amines also have the distinct advantage that they can react with peroxyl radicals to yield nitroxides, which can inhibit autoxidation in a catalytic manner utilizing the substrate itself as the stoichiometric reductant. Herein we provide an account of our recent efforts to understand how they manage this feat, which have revealed at least four mechanisms depending on the specific reaction conditions (i.e., saturated hydrocarbons at elevated temperatures, unsaturated hydrocarbons, acidic media, aqueous media/lipid dispersions). We also reiterate how their impressive RTA activity translates from solution to mammalian cell culture, wherein we have demonstrated that diarylamines and their derived nitroxides are potent inhibitors of ferroptosis, a recently characterized form of cell death associated with lipid peroxidation (autoxidation). In addition to phenols and amines, organosulfur compounds have long been used as antioxidants. The prevailing view has been that they undergo ionic reactions with product peroxides, preventing the initiation of further chain reactions. In recent years, we have found that many organosulfur compounds exhibit very good RTA activity. In particular, sulfenic acids (RSOH) and hydropersulfides (RSSH) are found to be among the best HAT agents known, particularly to peroxyl radicals where secondary orbital interactions are found to play a significant role. Consequently, oxidation of the sulfenic acid to a sulfinic acid greatly diminishes its HAT reactivity to peroxyls. Polysulfides and their oxides also undergo direct reactions with pero...

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“…Conventional kinetic studies have shown that overall rates of hydrocarbon autoxidation inhibited by 2,6-di-tert-butyl-4-substit~1ted phenols are proportional to the rate of chain initiation and inversely proportional to the phenol concentration (8, [10][11][12][13][14]. This implies that reaction of a chain carrying alkylperoxy radical and a phenol is bimolecular.…”

Section: 6-di-tert-butyl-4-s~bstit~1te~i Pl~enolsmentioning

confidence: 99%

Arrhenius Parameters for Reaction of tert-Butylperoxy Radicals with some Hindered Phenols and Aromatic Amines

Howard¹,

Furimsky²

1973

Can. J. Chem.

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The reaction of tert-butylperoxy radicals with some 2,6-di-iert-butyl-4-substituted phenols, a-naphthol, a-naphthylamine, and N-phenyl-a-naphthylaniine has been studied by following the change in radical concentration with time sing an e.p.r. spectrometer. Rates of radical decay were first-order in both reactants and were not influenced by the presence of teri-butyl hydroperoxide.Absolute values of the second-order rate constants were measured from -35 t o -100" and the preexponential factors and activation energies fell in the range lo4-lo5 M -' s -l and 0.5-1.0 kcal niol-l. Rate constants for deuterated phenols (OD) and aromatic amines (ND) were an order of magnitude lower than for the corresponding light compounds.There was no evidence for q u a n t~~m mechanical t~~n n e l i n g in these hydrogen atom transfer reactions and it would appear that the activation parameters are low because reaction initially involves the forniation of a hydrogen bonded peroxy radical -phenol (or aromatic anline) complex, followed by the transfer of a hydrogen atom within the coniplex.. . Can. J. Chem. 51, 3738 (1973)

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THE INHIBITION OF AUTOXIDATION BY 2,4,6-TRI-tert-BUTYL SUBSTITUTED PHENOL, ANILINE, AND THIOPHENOL

Cited by 16 publications

References 10 publications

Application of Cobalt/Peracetic Acid to Degrade Sulfamethoxazole at Neutral Condition: Efficiency and Mechanisms

Application of Cobalt/Peracetic Acid to Degrade Sulfamethoxazole at Neutral Condition: Efficiency and Mechanisms

Recent Insights on Hydrogen Atom Transfer in the Inhibition of Hydrocarbon Autoxidation

Arrhenius Parameters for Reaction of tert-Butylperoxy Radicals with some Hindered Phenols and Aromatic Amines

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