Topic
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: The large-curvature semiclassical ground-state tunneling approximation, version 3 (abbreviated LCG3) has been implemented for variational transition state theory calculations on systems with more than three atoms as discussed by the authors.
109 citations
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109 citations
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TL;DR: In this paper, the yields and chemical behavior of these intermediates were studied by pulse radiolysis of DCM solutions containing various solutes: phenols, anilines, dimethoxybenzene, hexamethylbenzenes, cyclohexene, dimethyl sulfoxide, and zinc tetratolylporphyrin.
Abstract: Radiolysis of dichloromethane (DCM) leads to formation of primary oxidizing radicals and carbon-centered radicals. The latter react with oxygen to yield peroxyl radicals. The yields and chemical behavior of these intermediates were studied by pulse radiolysis of DCM solutions containing various solutes: phenols, anilines, dimethoxybenzene, hexamethylbenzene, cyclohexene, dimethyl sulfoxide, and zinc tetratolylporphyrin. At low concentrations, some of these solutes were found to be oxidized by two peroxyl radicals, CH{sub 2}ClO{sub 2}{sup {sm bullet}} and CHCl{sub 2}O{sub 2}{sup {sm bullet}}, with different rate constants. At higher concentrations, the solutes react also with the primary radicals: Cl atoms and the radical cations CH{sub 2}Cl{sub 2}{sup +{sm bullet}}, with diffusion-controlled rate constants. The rates of these reactions were determined by competition kinetics because of the very short lifetimes of the species. Cl atoms were found to have a half-life of about 5 ns in DCM, reacting predominantly with the solvent by hydrogen abstraction. The radical cations decay within a fraction of a nanosecond. The total yield of these primary radicals was determined to be G = 3.6 and appears to be divided about equally between Cl and the radical cations. The total yield of oxidation, by the primary and the peroxyl radicals, wasmore » found to be G = 7.5. Cl atoms were found to be very reactive in electron transfer as well as addition and hydrogen abstraction reactions.« less
108 citations
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108 citations
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TL;DR: In this paper, the total energies at stationary points of the potential energy surfaces for the reaction systems were obtained at MP2 and MP4 levels and improved by using Gaussian-2 (G2) methodology.
Abstract: Ab initio calculations at different levels of theory have been performed for the title H-abstraction reactions. Total energies at stationary points of the potential energy surfaces for the reaction systems were obtained at MP2 and MP4 levels and improved by using Gaussian-2 (G2) methodology. The calculated G2 heats of reaction agree well with the experimental ones for both methoxy (product resulting from hydroxyl-side attack) and hydroxymethyl (product resulting from methyl-side attack) reaction channels. Calculations of the potential energy surfaces for the reaction systems show that H-abstraction from methanol by H, CH3, and OH (for methoxy reaction channel) proceeds by simple metathesis. The mechanism of the hydroxymethyl channel of reaction CH3OH + OH appears to be more complex, and it may consist of two consecutive processes. The reaction rate is determined by the energy barrier of the first process. Differences in the heights of the calculated energy barriers explain the differences in the reactivit...
108 citations