Oxidations of Amines. III. Duality of Mechanism in the Reaction of Amines with Chlorine Dioxide

Hull, Larry A.; Davis, George T.; Rosenblatt, David H.; Williams, Howell; Weglein, R. C.

doi:10.1021/ja00981a023

Cited by 94 publications

(59 citation statements)

References 1 publication

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“…11 and 12) is based on hydrogen abstraction Petryaev et al, 1984). Electron abstraction has been proved but only for tertiary amines (Dennis et al, 1967;Hull et al, 1967Hull et al, , 1969Rosenblatt et al, 1967). Fig.…”

Section: Oxidative Degradationmentioning

confidence: 99%

Amine degradation in CO2 capture. I. A review

Gouedard

Picq

Launay

et al. 2012

International Journal of Greenhouse Gas Control

429

321

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Section: Oxidative Degradationmentioning

confidence: 99%

Amine degradation in CO2 capture. I. A review

Gouedard

Picq

Launay

et al. 2012

International Journal of Greenhouse Gas Control

429

321

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“…N-Demethylation would be preferred if an aminium radical were an intermediate (20) because of the enhanced acidity of a methyl proton compared with an ethyl (78). If hydrogen atom abstraction were the preferred route, N-deethylation should be favored because the inductive effect should stabilize a substituted alkyl radical (91), and such patterns of C-hydroxylation have long been recognized for P450s (92). Indeed, in our studies of the oxidative cleavage of esters by P450, a reaction that occurs with a very high isotope effect and is considered to probably involve hydrogen atom abstraction, deethylation and deisopropylation were preferred over demethylation (93).…”

Section: Table II Kinetic Hydrogen Isotope Effects For N-demethylatiomentioning

confidence: 99%

Evidence for a 1-Electron Oxidation Mechanism in N-Dealkylation of N,N-Dialkylanilines by Cytochrome P450 2B1

Guengerich

Yun

Macdonald

1996

Journal of Biological Chemistry

157

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Many enzymes catalyze N-dealkylations of alkylamines, including cytochrome P450 (P450) and peroxidase enzymes. Peroxidases, exemplified by horseradish peroxidase (HRP), are generally accepted to catalyze N-dealkylations via 1-electron transfer processes. Several lines of evidence also support a 1-electron mechanism for many P450 reactions, although this view has been questioned in light of reported trends for kinetic hydrogen isotope effects for N-demethylation with a series of 4-substituted N,N-dimethylanilines. No continuous trend for an increase of isotope effects with the electronic parameters of para-substitution was seen for the P450 2B1-catalyzed reactions in this study. The larger value seen with the 4-nitro derivative is consistent with a shift in mechanism due to either a reversible electron transfer step preceding deprotonation or to a hydrogen atom abstraction mechanism. With HRP, the trend is to lower isotope effects with para electronwithdrawing substituents, due to an apparent shift in rate-limiting steps. Biomimetic model high-valent porphyrins showed reduction rates with variously 4-substituted N,N-dialkylanilines that were consistent with a positively charged intermediate; such relationships were not seen for anisole O-demethylation with P450 2B1. In contrast to the case with the NADPH-supported P450 reactions, high deuterium isotope effects (ϳ7) were seen in the N-dealkylations supported by the oxygen surrogate iodosylbenzene. With iodosylbenzene, colored aminium radicals were observed in the oxidations of aminopyrine, N,N-dimethyl-4-aminothioanisole, and 4-methoxy-N,N-dimethylaniline. With the latter compound, a substantial intermolecular deuterium isotope effect was observed for N-demethylation. In the N-dealkylation of N-ethyl,N-methylaniline by P450 2B1 (NADPH-supported), the ratio of N-demethylation to Ndeethylation was 16. Although it is probably possible for P450s to catalyze amine N-dealkylations via hydrogen atom abstraction when such a course is electronically or sterically favored, we interpret the evidence to favor a 1-electron pathway with N,N-dialkylamines with P450 2B1 as well as HRP and several biomimetic models.

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“…The primary degradation compounds are formed by either electron or hydrogen abstraction mechanisms (ammonia, aldehyde) or oxidation products of some of these compounds (acids). The initial mechanisms are still unclear, but the general impression is that the mechanisms either start with abstraction of an electron from the lone pair of nitrogen or abstraction of hydrogen from the nitrogen, α-carbon, or β-carbon, or a combination of these depending on the amine structure, nature of oxidants, pH, solvent effects and concentrations (Bedell, 2009;Chi and Rochelle, 2002;Rochelle, 2004, 2006;Hull et al, 1967;Hull et al, 1969;Rosenblatt et al, 1967;Sexton, 2008) Secondary degradation compounds are formed by reactions between primary degradation compounds and amines forming for example amides as N-(2-hydroxyethyl)-formamide (HEF), N-(2-hydroxyethyl)-acetamide (HEA) and N,-oxamide (BHEOX) from MEA and acid, or aldehyde and oxygen, and imidazoles as N-(2-hydroxyethyl)imidazole (HEI) from ammonia, MEA and several aldehydes. Lately several mechanisms have been suggested for the formation of secondary degradation compounds (da Silva et al, 2012;Lepaumier et al, 2011a;Strazisar et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Oxidative degradation of 2-ethanolamine: The effect of oxygen concentration and temperature on product formation

Vevelstad

Grimstvedt

Elnan

et al. 2013

International Journal of Greenhouse Gas Control

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Oxidative degradation experiments on 2-ethanolamine (MEA) were performed at four different oxygen concentrations and at two temperatures. MEA loss and degradation product build-up were measured. Increasing the temperature from 55 to 75 °C was shown to have higher impact on the MEA loss than increasing the oxygen concentration from 21 to 98%. Liquid end sample analyses were performed for all experiments and overall nitrogen balance tests were conducted for the experiments at 21% O2 (run 2), 50% O2 and 98% O2. Analysis of liquid and gas phase ammonia and MEA in the solvent was found to give a good overall picture of degradation in the MEA system. The degradation products formed at the different oxygen concentrations were the same as described in earlier literature. However, it was found that oxygen affects the formation of the individual degradation products differently. At 75 o C the development of degradation product concentrations with time was more complex. Laboratory reaction experiments were used to verify the formation of certain degradation products from some of the suggested mechanisms.

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Oxidations of Amines. III. Duality of Mechanism in the Reaction of Amines with Chlorine Dioxide

Cited by 94 publications

References 1 publication

Amine degradation in CO2 capture. I. A review

Amine degradation in CO2 capture. I. A review

Evidence for a 1-Electron Oxidation Mechanism in N-Dealkylation of N,N-Dialkylanilines by Cytochrome P450 2B1

Oxidative degradation of 2-ethanolamine: The effect of oxygen concentration and temperature on product formation

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