Reaction between NH₃ (Xˇ¹A₁) and CO (X¹ς⁺): A Computational Insight into the Reaction Mechanism of Formamide (H₂N-CHO) Formation

Formamide (NH₂CHO) is the smallest molecular unit that contains the basic peptide linkage and thus has recently attracted a great amount of interest in the field of astrochemistry. In this work using computational calculations, we have analyzed the three possible reaction paths for the reaction between CO and NH₃ to form formamide in both neutral-neutral and cation-neutral reaction surfaces. All of these three paths strongly favor the path of 1,2-hydrogen migration, which was discounted by previous studies in view of the constraints from steric factor. We have also analyzed the significant role played by prereaction complexes in these three reaction paths. We have proposed that for the neutral-neutral reaction path, formation of formamide in the low temperature interstellar clouds was hypothesized to proceed via hydrogen tunneling assisted by a tunneling ready like state as prereaction complex. On the other hand, for the two cation-neutral reactions, any tunneling cannot facilitate formation of formamide in the interstellar clouds. Rather in one case as all the stationary points are below the reactants, it can facilitate the reaction, whereas in the second case the reaction is only possible if it can get some catalytic assistance.