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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: The results indicate that neglect of multi-structural anharmonicity would lead to errors of factors of 0.3, 46, and 171 at 200, 1000, and 2400 K for this reaction.
Abstract: We estimated rate constants for the hydrogen abstraction from carbon-3 of 1-butanol by hydroperoxyl radical, a critically important reaction in the combustion of biofuel. We employed the recently developed multi-structural variational transition-state theory (MS-VTST), which utilizes a multifaceted dividing surface that allows us to include the contributions of multiple structures for reacting species and transition states. First, multiconfigurational Shepard interpolation—based on molecular-mechanics-guided interpolation of electronic-structure Hessian data obtained by the M08 HX/jun-cc-pVTZ electronic model chemistry—was used to obtain the portion of the potential energy surface needed for single-structure variational transition-state theory rate constants including multidimensional tunneling; then, the M08-HX/MG3S electronic model chemistry was used to calculate multi-structural torsional anharmonicity factors to complete the MS-VTST rate constant calculations. The lowest-energy structures of the trans...
58 citations
TL;DR: In this article, rate constants for the two-channel hydrogen-abstraction reactions CH3OH + Cl and Br were analyzed at different levels of theory and using several basis sets.
Abstract: Ab initio calculations at different levels of theory and using several basis sets have been performed for the title two-channel hydrogen-abstraction reactions CH3OH + Cl and Br. These calculations have shown that, similar to CH3OH + F, both reactions proceed via formation of intermediate complexes. Rate constant calculations for this type of reactions have been performed using the equations developed in Jodkowski, J. T.; Rayez, M.-T.; Rayez, J.-C.; Berces, T.; Sandor, D. J. Phys. Chem. 1998, 102, xxxx. The very low energy barrier for the hydroxymethyl channel of the CH3OH + Cl reaction obtained at the G2 level explains the relatively high value of the rate constant for this almost thermoneutral reaction. The very weak negative temperature dependence of the rate constant leading to CH2OH + HCl observed experimentally is also well reproduced by the calculations. For the CH3OH + Br reaction, both channels are endothermic, which explains the low values of the rate constants. A good agreement is obtained with ...
58 citations
58 citations
TL;DR: The effect of substituents on phenolic antioxidants was studied extensively in the 1960s as discussed by the authors, and it has been found that the introduction of a p -substituent such as an alkoxy or alkyl group develops antioxidant activity in o -methoxy phenols, although this phenol itself does not have any antioxidant activity.
58 citations
TL;DR: In this article, the density functional theory (DFT) approach has been used to analyze the adsorption of hydrogen on Al13 clusters and calculate the binding energy and electronic properties of the stable Al13+Hn assemblies.
Abstract: In this work, adsorption of hydrogen on Al13 clusters has been investigated theoretically using the density functional theory (DFT) approach. We have performed geometry optimization of atomic and molecular hydrogen in the proximity of Al13 and calculated the binding energy and electronic properties of the stable Al13+Hn assemblies. We have also calculated the energy barrier for the hydrogen atom transition between different adsorption sites on Al13 cluster as well as the activation energy for the dissociation and adsorption of molecular hydrogen. We found that the hydrogen atom adsorbs on the surface of Al13 cluster, without an energy barrier onto atop, bridge and hollow sites. A small barrier for H atom transition from one adsorption site to another together with the minor energy difference between the most stable isomers points towards high mobility of the hydrogen atom on the surface. The calculated dissociation–adsorption barrier for the hydrogen molecule of ∼14 kcal/mol and a desorption barrier of ∼1...
58 citations