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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: In this article, the C−H bond dissociation enthalpies of halomethanes were computed from the results of density functional theory (DFT) calculations at the B3LYP level with various basis sets, such as 6-311G(d,p) and 6- 311++G(3df,2p).
Abstract: The C−H bond dissociation enthalpies of halomethanes were computed from the results of density functional theory (DFT) calculations at the B3LYP level with various basis sets, such as 6-311G(d,p) and 6-311++G(3df,2p). Reasonably accurate C−H bond dissociation enthalpies were obtained even at the B3LYP/6-311G(d,p) level when ROB3LYP method was used for radicals. Applying the same procedure, the C−H bond dissociation enthalpies for a series of haloethanes were also calculated. Good correlation has been observed between the activation energies for the hydrogen abstraction from haloalkanes by OH radical and the corresponding C−H bond dissociation enthalpy values.
75 citations
TL;DR: In this article, a new molecular orbital based estimation method for the rate constants of degradation of organic compounds by hydroxyl radicals is introduced, which covers the three most important reaction mechanisms, i.e., the addition to carbon double bonds, the addition of aromatic rings and the hydrogen abstraction from aliphatic carbon atoms.
75 citations
TL;DR: Several fluorinated triplet aryl nitrenes have been generated in low-temperature polycrystals by photolysis of the corresponding azides as mentioned in this paper, and they have been detected by EPR.
Abstract: Several fluorinated triplet aryl nitrenes have been generated in low-temperature polycrystals by photolysis of the corresponding azides. Upon extended photolysis at {minus}196{degree}C the nitrenes abstract hydrogen from frozen toluene to give anilino-benzyl radical pairs, which subsequently combine to give CH insertion products. The radical pairs and the triplet nitrenes have been detected by EPR. In toluene solution, the major reaction products are tar, the corresponding fluorinated anilines, and azo compounds.
75 citations
TL;DR: In this article, the effect of irradiation of alkyl halides with methanol-O-d was studied in terms of initial homolytic cleavage of the carbon-halogen bond to afford a radical pair, which undergoes competing diffusion and hydrogen abstraction to give reduction products and electron transfer to afford an ion pair.
Abstract: Competing ionic and radical photobehavior has been observed for a number of alkyl halides. The proportion of nucleophilic substitution and reduction products were reported for each halide. Solvent effects of ethylene glycol, triethylamine, and methanol and atmospheric effects of nitrogen, oxygen, and air were studied. The effect of irradiation of the halides with methanol-O-d was reported. The results were discussed in terms of initial homolytic cleavage of the carbon-halogen bond to afford a radical pair, which undergoes competing diffusion and hydrogen abstraction to give reduction products and electron transfer to afford an ion pair. The ion pair, in turn, gives rise to the substitution and elimination products. (DDA)
75 citations
TL;DR: In this paper, the photocatalytic activity of anatase TiO2 depended significantly on the amount of metal or metal oxide present; the effect on the activity increased in the order platinum black ≫ platinum powder > ruthenium dioxide.
Abstract: Photoirradiation (λex > 300 nm) of Ar-purged aqueous propan-2-ol solution gave hydrogen and acetone in the presence of platinum- and/or ruthenium dioxide-loaded TiO2. The photocatalytic activity of anatase TiO2 depended significantly on the amount of metal or metal oxide present; the effect on the activity increased in the order platinum black ≫ platinum powder > ruthenium dioxide. The photocatalytic activity of rutile TiO2 was negligible even when loaded with platinum black. The effective wavelengths for the photocatalytic dehydrogenation of propan-2-ol were below ca. 390 nm, in agreement with the u.v. absorption spectrum of anatase TiO2. In a similar way primary, secondary and tertiary aliphatic alcohols underwent photocatalytic oxidation, accompanied by hydrogen liberation, by the platinized TiO2. The primary and secondary alcohols gave the corresponding carbonyl derivatives, while 2-methylpropan-2-ol and acetone gave dimeric products accompanied by stoichiometric hydrogen evolution. The initial rate of dehydrogenation in these photocatalytic systems was in proportion to the rate constants of hydrogen abstraction by hydroxyl radical in the homogeneous systems.
75 citations