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 oxidative transformation of primary amines to their corresponding oximes proceeds with high efficiency under molecular oxygen diluted with molecular nitrogen in the presence of the catalysts 1,1-diphenyl-2-picrylhydrazyl (DPPH) and tungusten oxide/alumina (WO3/Al2O3).
Abstract: The oxidative transformation of primary amines to their corresponding oximes proceeds with high efficiency under molecular oxygen diluted with molecular nitrogen (O2/N2 = 7/93 v/v, 5 MPa) in the presence of the catalysts 1,1-diphenyl-2-picrylhydrazyl (DPPH) and tungusten oxide/alumina (WO3/Al2O3). The method is environmentally benign, because the reaction requires only molecular oxygen as the terminal oxidant and gives water as a side product. Various alicyclic amines and aliphatic amines can be converted to their corresponding oximes in excellent yields. It is noteworthy that the oxidative transformation of primary amines proceeds chemoselectively in the presence of other functional groups. The key step of the present oxidation is a fast electron transfer from the primary amine to DPPH followed by proton transfer to give the α-aminoalkyl radical intermediate, which undergoes reaction with molecular oxygen and hydrogen abstraction to give α-aminoalkyl hydroperoxide. Subsequent reaction of the peroxide with WO3/Al2O3 gives oximes. The aerobic oxidation of secondary amines gives the corresponding nitrones. Aerobic oxidative transformation of cyclohexylamines to cyclohexanone oximes is important as a method for industrial production of e-caprolactam, a raw material for Nylon 6.
47 citations
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47 citations
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TL;DR: In this paper, density functional theory calculations at the B3LYP/6-31+G** level were employed to characterize the critical points for adducts, isomers, products, and intervening transition states for the reactions between benzene and the C2H or cyano (CN) radicals.
47 citations
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TL;DR: In this article, the potential energy surface of the C2H5O system was studied by high level ab initio methods using a simple transition state theory approach and the authors predicted high pressure bimolecular rate constants above 600 K for the following reactions under the condition that the pre-equilibrium is established.
Abstract: The potential energy surface of the C2H5O system was studied by high level ab initio methods. Unimolecular
rate constants have been computed using a simple transition state theory approach. The good agreement
between predicted and experimental high pressure limiting rate constants supported the reliability of the
proposed procedure. The direct bimolecular H-atom abstraction from ethylene by OH is unimportant and the reaction
proceeds ia the intermediate adduct. We predict high pressure bimolecular rate constants above 600 K for the following reactions under the condition that the pre-equilibrium is established:
We
also predict that the addition of H-atoms to acetaldehyde proceeds without an appreciable barrier and that
redissociation is efficient above 400 K and a thermal equilibrium will be established. We found the barrier for
addition of CH3 to formaldehyde to be 12 kJ mol−1 lower than the currently accepted barrier for the competing
hydrogen abstraction reaction leading to CH4+CHO.
47 citations
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TL;DR: In this paper, the authors use multiconfiguration self-consistent field methods to estimate the activation energy for hydrogen abstraction from gas-phase isobutane and then compute features of the potential energy surface for this same system imposing constraints that mimic those found in a diamond lattice.
Abstract: ion of terminal hydrogens on a diamond {111} surface by atomic hydrogen has been offered as the possible rate-determining elementary step in the mechanism of low-pressure diamond growth by chemical vapor deposition. We use ab initio multiconfiguration self-consistent-field methods to estimate the activation energy for this abstraction reaction. We do this by first computing features of the potential energy surface for hydrogen abstraction from gas-phase isobutane and then computing features of the potential energy surface for this same system imposing constraints that mimic those found in a diamond lattice. Our results therefore support the use in kinetic modeling or molecular dynamics simulations of activation energies taken from analogous gas-phase hydrocarbon reactions with little or no adjustment
47 citations