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.

A product study of the nitroxide inhibited thermal polymerization of styrene

Abstract: The efficient free radical scavengers 1,1,3,3-tetramethylisoindolinyl 2-oxy and 2,2,6,6-tetramethylpiperidinyl-1-oxy (nitroxides) disappear in styrene at 100°C with near zero order kinetics but at rates which are some 20 times higher than the known rate of initiation of thermal polymerization in the absence of scavenger A quantitative product analysis has shown that these inhibitors react by hydrogen abstraction from a thermally generated styrene dimer (1-phenyl-1,2,3,9-tetrahydronaphthalene) and to a minor extent by addition to the double bond of styrene monomer

Quasiclassical trajectory investigation of the reaction O( 1D)+H2

Abstract: A theoretical investigation of the energetics and dynamics of the O(1D)+H2 reaction is reported. Two different valence bond diatomics‐in‐molecules potential energy surfaces were used which differed only in the presence or absence of a small barrier to the C2v approach. The results of quasiclassical trajectory calculations were completely different on the two surfaces and showed that the dynamics of this exothermic reaction are sensitive to features of the surface at large internuclear distances. Reactions were found to occur by two possible mechanisms. In one mechanism, the oxygen atom abstracts a hydrogen atom from the end of the molecule in a direct reaction. Alternatively, the oxygen atom inserts into the H–H bond to form a collision complex which subsequently breaks apart. At all collision energies, the vibrational distribution of products from insertion/decomposition events is statistical while that of abstraction events is centered about v′ = 2. An inversion in the total populations of the levels v′...

Kinetics of the reaction of a secondary alkyl radical with tri-n-butylgermanium hydride and calibration of a secondary alkyl radical clock reaction

Abstract: Les parametres d'Arrhenius par la reaction du titre sont mesures en utilisant la cyclisation du radical hexene-5yle comme reaction d'etalonnage

Cytochrome P450 hydroxylation of hydrocarbons: variation in the rate of oxygen rebound using cyclopropyl radical clocks including two new ultrafast probes.

Abstract: The oxidation of eight methyl-substituted and three alkyl-substituted cyclopropanes by rat liver microsomal cytochrome P450 and pure reconstituted rabbit P450 2B4 was studied. Alkane hydroxylation catalyzed by P450 is generally believed to proceed by hydrogen abstraction followed by reaction of the carbon-centered radical with an iron-bound hydroxyl radical, a process called oxygen rebound. Hydrogen abstraction from methylcyclopropanes generates cyclopropylcarbinyl radicals whose solution rate constants for ring opening are known [Bowry, V.W., et al. (1991) J. Am. Chem. Soc. 113, 5687-5698]. Rearranged products were only observed with the five substrates which, upon hydrogen abstraction, would generate a cyclopropylcarbinyl radical that undergoes ring opening with a rate constant > or = 2.0 x 10(9) s-1 in solution. Values of the rate constants for oxygen rebound (kOH) were calculated by determining the ratio of unrearranged products (cyclopropylmethanols) to rearranged products (alkenols). For each substrate this ratio was generally about the same for the oxidations catalyzed by microsomal P450 and by P450 2B4. It is concluded that all of the substrates are oxidized via an intermediate cyclopropylcarbinyl radical. Two ultrafast probes, trans-1-methyl-2-phenylcyclopropane and 1,1-diphenyl-2-methylcyclopropane, gave alcohol product ratios which yielded unreasonably high values for kOH, viz., ca. 1.5 x 10(12) and ca. 7 x 10(12) s-1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)