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Catalytic Effect of a Single Water Molecule on the OH + CH2NH Reaction

Abstract

In recent work, there has been considerable speculation about atmospheric reaction of methylenimine (CH2NH), because this compound is highly reactive, soluble in water, and sticky, thus posing severe experimental challenges. In this work, we have revisited the kinetics of OH + CH2NH reaction assisted by a single water molecule. The potential energy surfaces (PESs) for water-assisted OH + CH2NH reaction were calculated using the CCSD(T)//BH&HLYP/aug-cc-pVTZ levels of theory. The rate coefficients for the bimolecular reaction pathways CH2NH···H2O + OH and CH2NH + H2O···HO were computed using canonical variational transition state theory (CVT) with small curvature tunneling correction. The reaction without water has four elementary reaction pathways, depending on how the hydroxyl radical approaches to CH2NH. In all cases, the reaction begins with the formation of single pre-reactive complex before producing abstraction and addition products. When water is added, the products of the reaction do not change, and the reaction becomes quite complex, yielding four different pre-reactive complexes and eight reaction pathways. The calculated rate coefficients for OH + CH2NH (water-free) reaction at 300 K is 1.7 × 10-11 cm3 molecule-1 s-1 and OH + CH2NH (water-assisted) is 5.1 × 10-14 cm3 molecule−1 s-1. This result is similar to its isoelectronic analogous reaction OH + CH2O (water-assisted). In general, the effective rate coefficients of water-assisted reaction is 2~3 orders of magnitude smaller than water-free. Our results show that water-assisted OH + CH2NH reaction cannot accelerate the reaction because the dominated water-assisted process depends parametrically on water concentration. As a result, the overall reaction rate coefficients are smaller.

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Publication details

The article was received on 18 Oct 2017, accepted on 09 Jan 2018 and first published on 10 Jan 2018


Article type: Paper
DOI: 10.1039/C7CP07091H
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Catalytic Effect of a Single Water Molecule on the OH + CH2NH Reaction

    A. A. Mohamad, B. M and K. Lin, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C7CP07091H

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