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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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45 citations
TL;DR: In this paper, the potential energy surface for the reaction of methoxy radical with carbon monoxide has been studied using the G2(B3LYP/MP2/CC) method.
Abstract: The potential energy surface for the reaction of methoxy radical with carbon monoxide has been studied using the G2(B3LYP/MP2/CC) method. Two reaction mechanisms were revealed. The hydrogen abstraction of CH3O by CO produces CH2O + HCO via a barrier of 24.19 kcal/mol. The addition of CH3O to CO proceeds to an intermediate CH3OCO via a barrier of 6.39 kcal/mol. The products, CH3 and CO2, can be formed in two ways. One is the C−O bond cleavage of the CH3OCO radical. The other involves the isomerization of CH3OCO to the CH3CO2 radical and the subsequent C−C bond fission. CH2O and HCO can be formed via the path CH3OCO → TS6 → IM4 → TS7 → CH2O + HCO. A radical product, CH2COOH, is formed through the hydrogen rearrangement of the CH3CO2 radical. Multichannel RRKM calculations have been carried out for the total and individual rate constants for various channels over a wide range of temperatures and pressures using the ab initio data. At lower temperatures, the title reaction is dominated by the stabilization of...
45 citations
TL;DR: Molecular dynamics simulations for two enzymatic conformers and examined the differences between the substrate-free and the bound enzymes find that F304, in the interface between the active and effector binding sites, is a key residue in the mechanism of cooperative binding.
Abstract: Cytochrome P450 3A4 (CYP3A4) is a key enzyme responsible for the metabolism of 50% of all orally administered drugs which exhibit an intriguing kinetic behavior typified by a sigmoidal dependence of the reaction velocity on the substrate concentration. There is evidence for the binding of two substrates in the active site of the enzyme, but the mechanism of this cooperative binding is unclear. Diazepam is such a drug that undergoes metabolism by CYP3A4 with sigmoidal dependence. Metabolism is initiated by hydrogen atom abstraction from the drug. To understand the factors that determine the cooperative binding and the juxtaposition of the C−H bond undergoing abstraction, we carried out molecular dynamics simulations for two enzymatic conformers and examined the differences between the substrate-free and the bound enzymes, with one and two diazepam molecules. Our results indicate that the effector substrate interacts both with the active substrate and with the enzyme, and that this interaction results in si...
45 citations
TL;DR: The kinetics of radical polymerization of styrene with nitroxide stable radicals and the corresponding hydroxylamines and secondary amine were investigated at 90 °C in this paper.
Abstract: The kinetics of radical polymerization of styrene with nitroxide stable radicals and the corresponding hydroxylamines and secondary amine were investigated at 90 °C The amine derivative was found to be inert The hydroxylamine causes retardation of polymerization The rate constant of termination of the styrene propagating radicals by hydroxylamines, Cx, was found to be 018−043, depending on the structure of the nitroxyl Nitroxide caused an induction period and retarded the rate after the induction period ended Both retardations are ascribed to hydrogen transfer In the case of hydroxylamines it is the result of hydrogen abstraction from the hydroxyl group of the hydroxylamine by the polystyryl radical In the case of nitroxides, it is suggested that retardation is caused by hydroxylamine formed as a byproduct during the induction period when the nitroxide reacts with the propagating radical This is generally a minor side reaction of the propagating radical scavenging by nitroxyl radicals, but this
45 citations
TL;DR: A series of 4-substituted cubyl radicals was generated by bromine atom abstraction from 1-bromo-4-substantuted cubanes as discussed by the authors.
Abstract: A series of 4-substituted cubyl radicals was generated by bromine atom abstraction from 1-bromo-4-substituted cubanes. EPR observations showed that the cubyl radicals abstracted secondary hydrogen atoms from the ethyl groups of triethylsilane and decayed mainly by second-order combination reactions. tert-Butoxyl radicals abstracted hydrogen atoms from cubane at least 26 times more rapidly than from cyclopropane at -90 o C. Electron-withdrawing substituents on cubane greatly reduced this rate. tert-Butoxyl radicals selectively abstracted the cage hydrogens rather than primary methyl hydrogens from methylcubane
45 citations