Reacciones primarias de abstracción de hidrógeno del trans-1,3-butadieno mediante radical hidroxilo
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Rev. Bol. Quim
Abstract
Se han investigado en forma teórica los canales de abstracción de los hidrógenos del 1,3-butadieno (C4H6) por hidroxilo radical, en su estado electrónico fundamental, en fase gaseosa y en condiciones normales de presión y temperatura. Se realizó un estudio de los rotámeros del C4H6, habiéndose encontrado que el confórmero trans es 12,3 kJ/mol más estable que la forma cis. Se determinaron tres canales distintos de abstracción de hidrógenos del C4H6, debido a la presencia de sus tres protones químicamente no equivalentes. Se caracterizaron todas las estructuras moleculares involucradas en cada canal reactivo, confirmados por sus frecuencias vibracionales, coordenada intrínseca de reacción (IRC) y vectores de transición. Se utilizó el método del funcional de la densidad (DFT), con el funcional híbrido B3LYP y base de Dunning aug-cc-pVTZ, incorporados en el paquete Gaussian 03. En todos los casos se procedió a extrapolar la energía al límite de base completa (CBS) utilizando un método exponencial y aplicando correcciones de la energía del punto cero (ZPE). Se reportan energías de activación negativas para los tres canales de reacción y la formación de complejos posreactivos.
The abstraction channels of 1,3-butadiene (C4H6) hydrogens by radical hydroxyl have been theoretically investigated, in their fundamental electronic state, in the gas phase and under normal conditions of pressure and temperature. A study of the C4H6 rotamers was performed, having found that the trans conformer is 12,3 kJ / mol more stable than the cis forra Three different C4H6 hydrogen abstraction channels were determined, due to the presence of its three chemically non-equivalent protons. All molecular structures involved in each reactive channel were characterized, confirmed by their vibrational frequencies, intrinsic reaction coordinate (IRC) and transition vectors. The density functional method (DFT) was used, with the hybrid functional B3LYP and Dunning base aug-cc-pVTZ, incorporated in the Gaussian 03 package. In all cases the energy was extrapolated to the base limit Complete (CBS) using a exponential method and applying zero point energy corrections (ZPE). Negative activation energies are reported for the three reaction channels and the formation of post-reactive complexes.
The abstraction channels of 1,3-butadiene (C4H6) hydrogens by radical hydroxyl have been theoretically investigated, in their fundamental electronic state, in the gas phase and under normal conditions of pressure and temperature. A study of the C4H6 rotamers was performed, having found that the trans conformer is 12,3 kJ / mol more stable than the cis forra Three different C4H6 hydrogen abstraction channels were determined, due to the presence of its three chemically non-equivalent protons. All molecular structures involved in each reactive channel were characterized, confirmed by their vibrational frequencies, intrinsic reaction coordinate (IRC) and transition vectors. The density functional method (DFT) was used, with the hybrid functional B3LYP and Dunning base aug-cc-pVTZ, incorporated in the Gaussian 03 package. In all cases the energy was extrapolated to the base limit Complete (CBS) using a exponential method and applying zero point energy corrections (ZPE). Negative activation energies are reported for the three reaction channels and the formation of post-reactive complexes.
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Vol. 36, No. 3