Classical dynamics simulations of interstellar glycine formation via $$\hbox {CH}_{2} = \hbox {NH} + \hbox {CO} + \hbox {H}_{2}\hbox {O}$$ CH 2 = NH + CO + H 2 O reaction

Abstract

Formation of simple organic species such as glycine in the interstellar medium and transportation to earth via meteorites is considered to be a possible route for ‘Origin of Life’ on earth. Glycine formation has been proposed to occur via two different pathways involving formaldehyde ( $$\hbox {HCHO}$$ ) and methanimine ( $$\hbox {CH}_{2} = \hbox {NH}$$ ) as key intermediates. In the second pathway, which is the topic of this paper, $$\hbox {CH}_{2} = \hbox {NH}$$ reacts with $$\hbox {CO}$$ and $$\hbox {H}_{2} \hbox {O}$$ forming neutral glycine. In a recent article (Nhlabatsi et al. in Phys. Chem. Chem. Phys. 18:375, 2016), detailed electronic structure calculations were reported for the reaction between $$\hbox {CH}_{2} = \hbox {NH}$$ , $$\hbox {CO}$$ and $$(\hbox {H}_{2} \hbox {O})_n$$ , $$n = 1, 2, 3$$ , and 4, forming glycine in the interstellar media. The presence of additional water molecule(s) for this reaction reduces reaction barrier - thus exhibiting a catalytic effect. This effect was described in terms of efficient proton transfer mediated by the additional water molecule through a relay transport mechanism. In the present article, we report ab initio classical trajectory simulations for the interstellar formation of glycine for the above mentioned reaction with $$n = 1$$ and 2. The trajectories were generated on-the-fly over a density functional B3LYP/6-31++G(3df,2pd) potential energy surface. Our simulations indicate that the above proposed catalytic effect by the additional water molecule(s) may not be a classical effect. Synopsis: Glycine formation in the interstellar media via the $$\hbox {CH}_{2} = \hbox {NH} + \hbox {CO} + \hbox {H}_{2} \hbox {O}$$ reaction was investigated by classical chemical dynamics simulations. This reaction has a large barrier which reduces in presence of additional water molecules. Our simulations indicate that the proposed catalytic effect by the additional water molecules may not be a classical effect.