A product branching ratio controlled by vibrational adiabaticity and variational effects: Kinetics of the H + trans-N 2H 2 reactions

Jingjing Zheng, Roberta J. Rocha, Marina Pelegrini, Luiz F.A. Ferrão, Edson F.V. Carvalho, Orlando Roberto-Neto, Francisco B.C. MacHado, Donald G. Truhlar

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Abstract

The abstraction and addition reactions of H with trans-N 2H 2 are studied by high-level ab initio methods and density functional theory. Rate constants were calculated for these two reactions by multistructural variational transition state theory with multidimensional tunneling and including torsional anharmonicity by the multistructural torsion method. Rate constants of the abstraction reaction show large variational effects, that is, the variational transition state yields a smaller rate constant than the conventional transition state; this results from the fact that the variational transition state has a higher zero-point vibrational energy than the conventional transition state. The addition reaction has a classical barrier height that is about 1 kcalmol lower than that of the abstraction reaction, but the addition rates are lower than the abstraction rates due to vibrational adiabaticity. The calculated branching ratio of abstraction to addition is 3.5 at 200 K and decreases to 1.2 at 1000 K and 1.06 at 1500 K.

Original languageEnglish (US)
Article number184310
JournalJournal of Chemical Physics
Volume136
Issue number18
DOIs
StatePublished - May 14 2012

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    Zheng, J., Rocha, R. J., Pelegrini, M., Ferrão, L. F. A., Carvalho, E. F. V., Roberto-Neto, O., MacHado, F. B. C., & Truhlar, D. G. (2012). A product branching ratio controlled by vibrational adiabaticity and variational effects: Kinetics of the H + trans-N 2H 2 reactions. Journal of Chemical Physics, 136(18), [184310]. https://doi.org/10.1063/1.4707734