Browsing by Author "Gutierrez-Oliva, Soledad"

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    An extension of the Marcus equation: the Marcus potential energy function
    (2018) Gutierrez-Oliva, Soledad; Herrera Pisani, Bárbara Andrea; Toro Labbé, Alejandro
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    Correspondence between the reaction force minimum and the onset of abrupt variations of the kinetic and potential energies in bond dissociation and formation
    (2024) Politzer, Peter; Gutierrez-Oliva, Soledad; Clark, Timothy; Murray, Jane S.
    ContextWe demonstrate that the minimum of the reaction force curve of a diatomic or polyatomic molecule undergoing bond dissociation is significant in several respects. As has been pointed out in the past, it is the point at which the force opposing dissociation is strongest. It marks the boundary between the primarily structural stage of a bond dissociation (stretching) and the transition region between the stretched bond and independent atoms. We now show that the reaction force minimum is also where the kinetic and potential energy curves tend to change direction abruptly. At this point, the total energy E(R) has increased by about 27% of the dissociation energy, for both diatomic and polyatomic molecules.MethodsDissociation curves are analyzed at the UHF/daug-cc-pV5Z level of theory using Gaussian 16.
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    Digging on the mechanism of some Diels-Alder reactions: the role of the reaction electronic flux
    (2023) Hernandez-Mancera, Jennifer Paola; Vivas-Reyes, Ricardo; Gutierrez-Oliva, Soledad; Herrera, Barbara; Toro-Labbe, Alejandro
    Within the framework of the reaction force analysis, numerical data obtained from DFT calculations were used to characterize the mechanism of three Diels-Alder reactions involving three substituted furandione as dienophile, and a chiral anthracene, as diene. Then, the Marcus potential energy function and the activation strain model were used to rationalize the energetics of the reactions and to obtain physical insights on the nature of activation energies. It has been found that the activation processes are dominated by structural arrangements of reactants, basically due to the approach of the diene to the dienophile to start the reaction. Besides, the electronic activity taking place along the reaction coordinate have been analyzed through the reaction electronic flux. It has been found that the electronic activity that emerge more intensively within the transition-state region, is mainly due to electronic transfer effects, due to the breaking and forming & pi; bonds. Although polarization effects are also present but to a lesser extent.
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    Effect of the cyano group in the HAVA mechanism for PAHs formation: a reaction force analysis for the reaction between benzonitrile (C6H5CN) and vinylacetylene
    (2024) Saide, Alessandra C. Misad; Gutierrez-Oliva, Soledad
    Due to the importance and fascination that arises from processes involving Polycyclic Aromatic Hydrocarbon (PAHs) in the interstellar medium (ISM), in this work quantum calculations were used to study the HAVA mechanism (Hydrogen Abstraction Vinylacetylene Addition) involved in the PAHs formation from the benzonitrile (${\rm C_6H_5CN}$), molecule recently discovered in the ISM, and vinylacetylene (${\rm C_4H_4}$). The reaction force analysis was used to obtain information about the mechanisms in terms of structural and electronic rearrangements presents in the formation of naphthalene, 1-naphthonitrile, 2-naphthonitrile, and 3-ethynylisoquinoline. Due to the presence of the cyano group on the aromatic ring for the formation of 1-naphthonitrile and 2-naphthonitrile, these reactions: (a) follow the HAVA mechanism, showing the same structural nature of the submerged energy barriers and (b) result consistent with the fact that both molecules have recently been found in TMC-1, where benzonitrile and vinylacetylene are also present. The mesomeric and inductive effect of the cyano group on the aromatic ring contributes to lowering the energy barrier when the radical is in the ortho position on the aromatic ring with respect to the cyano group. This decrease contributes greatly to the work of electronic reordering. Although the formation of 3-ethynylisoquinoline (N-Heterocycle) does not follow the HAVA mechanism and involves positive barriers at the conditions of TMC-1, important astrochemical and astrobiological implications can be derived from this result, since N-containing heterocycles, have been detected in carbonaceous chondrites would be providing interesting connection between chemistry in space and the origin of life on Earth.
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    Link between reaction force and DFT reactivity descriptors
    (2006) Gutierrez-Oliva, Soledad; Herrera Pisani, Barbara Andrea; Toro-Labbe, Alejandro