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Hydrogen atom abstraction

About: Hydrogen atom abstraction is a research topic. Over the lifetime, 7059 publications have been published within this topic receiving 151781 citations.


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TL;DR: Findings indicate that quantum mechanical tunneling plays an important role in these reactions of PINO(*) with substituted toluenes, benzaldehydes, and benzyl alcohols, and the second-order rate constants were correlated by means of a Hammett analysis.
Abstract: The phthalimide N-oxyl (PINO) radical was generated by the oxidation of N-hydroxyphthalimide (NHPI) with Pb(OAc)4 in acetic acid. The molar absorptivity of PINO• is 1.36 × 103 L mol-1 cm-1 at λmax 382 nm. The PINO radical decomposes slowly with a second-order rate constant of 0.6 ± 0.1 L mol-1 s-1 at 25 °C. The reactions of PINO• with substituted toluenes, benzaldehydes, and benzyl alcohols were investigated under an argon atmosphere. The second-order rate constants were correlated by means of a Hammett analysis. The reactions with toluenes and benzyl alcohols have better correlations with σ+ (ρ = −1.3 and −0.41), and the reaction with benzaldehydes correlates better with σ (ρ = −0.91). The kinetic isotope effect was also studied and significantly large values of kH/kD were obtained: 25.0 (p-xylene), 27.1 (toluene), 27.5 (benzaldehyde), and 16.9 (benzyl alcohol) at 25 °C. From the Arrhenius plot for the reactions with p-xylene and p-xylene-d10, the difference of the activation energies, EaD − EaH, was 12...

116 citations

Journal ArticleDOI
TL;DR: It is shown that DEE inhibits the reactivity of an equimolar mixture of hydrogen and oxygen (1% of each) and that the unimolecular decomposition and hydrogen atom abstraction of DEE and the decomposition of the ethoxy radical have the largest influence.
Abstract: The pyrolysis and oxidation of diethyl ether (DEE) has been studied at pressures from 1 to 4 atm and temperatures of 900−1900 K behind reflected shock waves. A variety of spectroscopic diagnostics have been used, including time-resolved infrared absorption at 3.39 μm and time-resolved ultraviolet emission at 431 nm and absorption at 306.7 nm. In addition, a single-pulse shock tube was used to measure reactant, intermediate, and product species profiles by GC samplings at different reaction times varying from 1.2 to 1.8 ms. A detailed chemical kinetic model comprising 751 reactions involving 148 species was assembled and tested against the experiments with generally good agreement. In the early stages of reaction the unimolecular decomposition and hydrogen atom abstraction of DEE and the decomposition of the ethoxy radical have the largest influence. In separate experiments at 1.9 atm and 1340 K, it is shown that DEE inhibits the reactivity of an equimolar mixture of hydrogen and oxygen (1% of each).

115 citations

Journal ArticleDOI
TL;DR: The absolute rate constant for hydrogen abstraction from dilinoleoylphosphatidylcholine (DLPC) bilayers photoinitiated by benzophenone takes place by a free radical chain mechanism as mentioned in this paper.
Abstract: Autoxidation of dilinoleoylphosphatidylcholine (DLPC) bilayers photoinitiated by benzophenone takes place by a free radical chain mechanism according to product studies of the cis, trans and trans, trans-9- and -13-linoleate hydroperoxides formed and kinetic studies of the reaction order as a function of light intensity. The absolute rate constant for hydrogen abstraction from DLPC bilayers by peroxyl radicals is found to be 36.1 M−1 s−1 at 37 °C. Preliminary measurements of activities of phenolic antioxidants, α-tocopherol (α-T), 2,2,5,7,8-pentamethyl-6-hydroxychroman (PMHC), 2,5,7,8-tetramethyl-6-hydroxychroman-2-carboxylate (Trolox), and 2,6-di-tert-butyl-4-methylphenol (BHT) by oxygen uptake studies during inhibition periods using photoinitiation gave uncorrected inhibition rate constants, Kinh, for α-T, PMHC, and Trolox several orders of magnitude lower than observed earlier in chlorobenzene. Three series of phenolic antioxidants, (a) polyalkyl-6-hydroxychromans, (b) polyalkyl-4-methoxyphenols, and (...

114 citations

Journal ArticleDOI
TL;DR: A mechanistic study of HAT by an isolable iron(III) imido complex, L(Me)FeNAd, which shows a strong dependence on the size of the hydrocarbon substrate and a strategy that has promise for controlling the regioselectivity of these C-H bond activation reactions.
Abstract: This article discusses a mechanistic study of hydrogen atom transfer by an isolable iron (III) imido complex, LᴹᵉFeNAd (Lᴹᵉ = bulky β-diketiminate ligand, 2,4-bis(2,6-diisopropylphenylimido)pentyl; Ad = 1-adamantyl).

114 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202382
2022142
2021120
2020121
2019104
2018124