Decomposition of acetyl peroxide in the presence of acetate salts

Koenig, Tamas; Wielesek, R.A.

doi:10.1021/ja01038a027

Cited by 6 publications

(7 citation statements)

References 2 publications

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“…Using 14 C acetate labelling, these authors did note some incorporation of the acetate base into the product acetoxyacetic acid, which could occur via several different radical and non-radical pathways. 49 However, they found that 55-70% of this product was not isotopically labelled, suggesting that the acetate could also simply act as a base catalyst. 49 These observations are entirely consistent with an enolization mediated decomposition mechanism.…”

Section: Keto-enol Tautomerism In N-acyloxyamines Diacyl Peroxides and N-acyloxy Phthalimidesmentioning

confidence: 99%

“…49 However, they found that 55-70% of this product was not isotopically labelled, suggesting that the acetate could also simply act as a base catalyst. 49 These observations are entirely consistent with an enolization mediated decomposition mechanism. As Figure S1 in the supporting information indicates, the enol tautomer of the acetyl peroxide is unstable relative to its fragmentation products on the Gibbs Free Energy Surface.…”

Section: Keto-enol Tautomerism In N-acyloxyamines Diacyl Peroxides and N-acyloxy Phthalimidesmentioning

confidence: 99%

“…Pleasingly, Wielesek and co-workers actually reported conclusive evidence for enolization in acetyl peroxide decomposition around 50 years ago. 49 These authors found that acetyl peroxide readily reacts, in the presence of acetate salts at room temperature, to afford 2-acetoxyacetic acid. 49 Unsurprisingly, this reaction was inhibited by the neutralization of acetate with added acetic acid.…”

Section: The Journal Of Organic Chemistrymentioning

confidence: 99%

“…49 These authors found that acetyl peroxide readily reacts, in the presence of acetate salts at room temperature, to afford 2-acetoxyacetic acid. 49 Unsurprisingly, this reaction was inhibited by the neutralization of acetate with added acetic acid. Using 14 C-acetate labeling, these authors did note some incorporation of the acetate base into the product acetoxyacetic acid, which could occur via several different radical and nonradical pathways.…”

Section: The Journal Of Organic Chemistrymentioning

confidence: 99%

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Mechanistic Insights into N-Acyloxyamine-Initiated Controlled Degradation of Polypropylene: The Unexpected Role of Keto–Enol Tautomerization in Carboxylate Radical Chemistry

Noble

Nesvadba²,

Coote

2019

J. Org. Chem.

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Controlled degradation of polypropylene (PP) is used industrially to improve the properties of crude PP. While traditionally initiated by organic peroxides, N-acyloxyamines are now preferred due to their greater stability. However, their mechanism of action remains unclear. Using high level ab initio calculations, we show that N-O homolysis is the most likely fragmentation pathway available to N-acyloxyamines, in contrast to the more usual C-O homolysis observed for the closely related N-alkoxyamines. This would, in theory, generate aminyl and carboxylate radicals, with the latter undergoing decarboxylation to generate methyl radicals. However, the enol-form of N-acyloxyamines is significantly less thermally stable, having bond dissociation free energies that are over 50 kJ/mol below that of their keto equivalent. Under conditions where keto-enol tautomerism is feasible, enol N-O homolysis, which forms the more stable acetic acid radical, would be the dominant degradation pathway. This reveals the crucial and underappreciated role that polar impurities play in the initiation process of enolizable initiators and may explain contradictory observations in the experimental literature. The product aminyl radicals are susceptible to β-fragmentation, releasing alkyl radicals and affording imines, which in turn are susceptible to allylic H-abstraction and further β-fragmentation leading to dialkyl pyridines as the ultimate degradation products.

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Section: Keto-enol Tautomerism In N-acyloxyamines Diacyl Peroxides and N-acyloxy Phthalimidesmentioning

confidence: 99%

Section: Keto-enol Tautomerism In N-acyloxyamines Diacyl Peroxides and N-acyloxy Phthalimidesmentioning

confidence: 99%

Section: The Journal Of Organic Chemistrymentioning

confidence: 99%

Section: The Journal Of Organic Chemistrymentioning

confidence: 99%

See 2 more Smart Citations

Mechanistic Insights into N-Acyloxyamine-Initiated Controlled Degradation of Polypropylene: The Unexpected Role of Keto–Enol Tautomerization in Carboxylate Radical Chemistry

Noble

Nesvadba²,

Coote

2019

J. Org. Chem.

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“…[3,4] The conformational transitions of water soluble polymers were investigated in works [5,6] by using Raman spectroscopy, experimental titrations, fluorescence correlation spectroscopy [7] and other methods. [8,9] The weak polyelectrolytes such as poly(acrylic acid) are very sensitive to pH and chains are almost uncharged at low pH however are fully charged at high pH. Authors of work [10] reported that the conformation on PAA adsorbed on alumina estimated using a pyrene-labeled polymer changes appreciably with pH and affects the dispersion stability of polymer-protein complex solution.…”

Section: Introductionmentioning

confidence: 99%

Conformational Dynamics of Poly(acrylic acid)‐Bovine Serum Albumin Polycomplexes at Different pH Conditions

Akkiliç

Mustafaev

Chegel³

2008

Macromolecular Symposia

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This work presents the real time surface plasmon resonance (SPR) and fluorescence spectroscopy observation of cooperative interactions between aggregate-forming bovine serum albumin (BSA) and oppositely charged linear macromolecule poly(acrylic) acid (PAA). Interactions between protein and polymer result in formation of polyelectrolyte-protein polycomplexes, which exhibit expressed conformational transformations, especially at low pH. The rate constants of observed kinetic transformations were calculated and found to vary in the range from 0.8 Â 10 À3 to 6.7 Â 10 À3 for different pH values. The processes of aggregation, sedimentation and conformation of BSA-PAA complex are discussed.

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Aromatische Diazoniumsalze, VIII: Der Mechanismus der Indazolsynthese aus o‐Toluoldiazoniumsalzen

1978

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Die Synthese verschiedener substituierter Indazole 6 aus substituierten o-Toluoldiazoniumsalzen 3 oder N-Nitroso-o-acetotoluidid 2 in Anwesenheit von DzO oder CH3C02D erfolgt ohne D-Einbau in die Diazoniumsalze 3. -Die Synthese von 3-Methyl-3H-indazol-3-carbonsauremethylester (23) aus optisch aktivem 2-[ 1 -(Methoxycarbonyl)ethyl]benzoldiazoniumsalz 21 erfolgt sowohl in Wasser als auch in der Jacobsonschen Indazolsynthese in Benzol unter vollstandigerRacemisierung. Es wird geschlossen, daB die 5-Diazo-6-methylen-1,3-cyclohexadien-Zwischenstufen 1 bzw. 24 durchlaufen werden, die schneller durch intramolekulare Kupplung bzw. 10nelektrocyclische Reaktion cyclisieren als Reprotonierung zu 3 erfolgt. Aromatic Diazonium Salts, VIII') The Mechanism of the Synthesis of Indazole from o-Toluenediazonium SaltsThe synthesis of several substituted indazoles 6 from substituted o-toluenediazonium salts 3 or from N-nitroso-o-acetotoluidide 2 in the presence of DzO or CH3COzD is not accompanied by D-incorporation into the diazonium salts3. -Racemic methyl 3-methyl-3H-indazole-3-carboxylate (23) was obtained from optically active 2-[ 1-(methoxycarbonyl)ethyl]benzenediazonium salt 21 in water or by the Jacobson synthesis in benzene. The 5-diazo-6-methylene-1,3-cyclohexadiene 1 and 24, respectively, are proposed as intermediates of these reactions. Their cyclisations by an intramolecular coupling reaction or by a lor electrocyclic reaction are apparently faster than their protonation under the reaction conditions. Aromatische Diazoniumsalze konnen mit o-stindigen Substituenten, die ein freies Elektronenpaar tragen, durch intramolekulare Kupplung RingschluDreaktionen zu Wnfgliedrigen benzoanellierten Heterocyclen eingehen 'I. Diese Voraussetzung ist bei der Synthese von Indazolen 6 aus o-Toluoldiazoniumsalzen 341 oder bei der verwandten Jacobsonschen Indaz~lsynthese~~ 'I aus N-Nitroso-o-acetotoluidid 2 nicht direkt gegeben.VII. Mitteil.:

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Decomposition of acetyl peroxide in the presence of acetate salts

Cited by 6 publications

References 2 publications

Mechanistic Insights into N-Acyloxyamine-Initiated Controlled Degradation of Polypropylene: The Unexpected Role of Keto–Enol Tautomerization in Carboxylate Radical Chemistry

Mechanistic Insights into N-Acyloxyamine-Initiated Controlled Degradation of Polypropylene: The Unexpected Role of Keto–Enol Tautomerization in Carboxylate Radical Chemistry

Conformational Dynamics of Poly(acrylic acid)‐Bovine Serum Albumin Polycomplexes at Different pH Conditions

Aromatische Diazoniumsalze, VIII: Der Mechanismus der Indazolsynthese aus o‐Toluoldiazoniumsalzen

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