Atmospheric Gas Phase Chemistry of CH sub(2)=NH and HNC. A First-Principles Approach

Quantum chemical methods were used to investigate the OH initiated atmospheric degradation of methanimine, CH sub(2)=NH, the major primary product in the atmospheric photo-oxidation of methylamine, CH sub(3)NH sub(2). Energies of stationary points on potential energy surfaces of reaction were calcul...

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Bibliographic Details
Published in:The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2014-07, Vol.118 (28), p.5279-5288-5279-5288
Main Authors: Bunkan, Arne Joakim C, Tang, Yizhen, Sellevag, Stig R, Nielsen, Claus J
Format: Article
Language:English
Subjects:
Atmospherics
Carbon
Clusters
Degradation
Gas phases
Mathematical models
Nitrous oxides
Scission
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Summary:Quantum chemical methods were used to investigate the OH initiated atmospheric degradation of methanimine, CH sub(2)=NH, the major primary product in the atmospheric photo-oxidation of methylamine, CH sub(3)NH sub(2). Energies of stationary points on potential energy surfaces of reaction were calculated using multireference perturbation theory and coupled cluster theory. The results show that hydrogen abstraction dominates over the addition route in the CH sub(2)=NH + OH reaction, and that the major primary product is HCN, while HNC and CHONH sub(2) are minor primary products. HNC is found to react with OH exclusively via addition to the carbon atom followed by O-H scission leading to HNCO; N sub(2)O is not a product in the atmospheric photo-oxidation of HNC. Additional G4 calculations of the CH sub(2)=NH + O sub(3) reaction show that this is too slow to be of importance at atmospheric conditions. Rate coefficients for the CH sub(2)=NH + OH and HNC + OH reactions were calculated as a function of temperature and pressure using a master equation model based on the coupled cluster theory results. The rate coefficients for OH reaction with CH sub(2)=NH and HNC at 1000 mbar and room temperature are calculated to be 3.0 x 10 super(-12) and 1.3 x 10 super(-11) cm super(3) molecule super(-1) s super(-1), respectively. The atmospheric fate of CH sub(2)=NH is discussed and a gas phase photo-oxidation mechanism is presented.
ISSN:1089-5639
1520-5215
DOI:10.1021/jp5049088