Activation barriers for series of exothermic homologous reactions. I. Metal atom reactions with N2O

Abstract

We recently observed that the activation barriers of O-atom abstraction reactions between metal atoms and N2O, in which both reactants are in their ground electronic states and the atoms contain no valence p electrons, vary systematically with the sums of the metal atom ionization potential and the energy required to promote a valence s electron to the lowest p orbital. It is shown here that this observation can be explained by the assumption that the activated complex results from the resonance interactions of ionic and covalent structures. Activation barriers for 43 reactions are calculated and where experimental measurements are available, are shown to be in good agreement with those. New interpretations are offered for literature data on the Ca and Cr reactions. The resonance treatment leads to a more general relationship in which activation barriers depend simultaneously on ionization potentials, electron affinities, promotion energies, and bond energies of the reactants. A number of further series of reactions, where activation barrier or rate coefficient trends with some of these parameters have been observed, are discussed and seen to be special cases of this formalism. Good agreement is found between the height of the barrier for the N2O+H→N2+OH reaction calculated by the present resonance treatment and an ab initio method.

Depletion kinetics of low-lying states of tungsten in the presence of NO, N2O, and SO2

“…This coincides with [27]. In this model, activation barriers are calculated by taking into account the ionization potential and sp promotion energy of the metal, the electron affinity of N 2 O and the bond energy of the metal oxide product.…”

Kinetic study of the reaction of Mn(a6S5/2) with N2O from 448 to 620 K

“…3 Clearly, the resonance interaction model does not accurately predict the barrier for this reaction. It is not surprising that this model does not accurately predict the kinetic behavior of transition metals due to the neglect of both the TM's d electrons and the product metal oxide's electronic structure.…”

“…Arguments were presented which predicted significant barriers should also be present for the production of ground state MnO, although no quantitative results were presented. Recently, Fontijn and co-workers have advanced a resonance interaction model [3][4][5][6] to predict Arrhenius parameters and rate constants for metal atoms reacting with N 2 O. In this model, the activation barriers are calculated by taking into account the ionization potential and sp promotion energy of the metal, the electron affinity of N 2 O, and the bond energy of the metal oxide product.…”

Control of Toxic Metal Emissions from Combustors Using Sorbents: A Review

“…70 They used a high-temperature fast flow reactor with photochemical techniques for the measurement of reaction rates in the 300-1,900 K temperature range. Futerko and Fontijn [71][72][73] have reported activation energies for a series of exothermic homologous reactions for Ca and Cr species. Vijh 74,75 examined the relationship of the activation energy to the heat of formation for metal-oxygen reactions for Mn, Co, Ni, and Pb species.…”