Hydrogenations of Isocyanic Acid: A Computational Study on Four Possible Concerted Paths for Formamide Formation

Interstellar formations and significances of formamide as a possible prebiotic precursor, for many complex organic molecules of life are well studied in recent times. In this work, computational studies (B3LYP, wB97xD, MP2, and CCSD(T)) have been carried out to study the formation mechanism of formamide, from HNCO + H₂, via concerted paths. Beside the well-studied, Direct Route, three new routes, imine, carbene and Oxime intermediate routes have been investigated. Carbene and oxime routes were found to be endothermic and hence may not be useful in interstellar circumstances. On the other hand, imine route, being slightly exothermic, may be considered as an auxiliary channel to the direct route. Detailed studies for these two routes have been carried out. Also, based only on a qualitative analysis of possibility of tunnelling, we have suggested the possible usefulness of these two reaction paths in cryogenic conditions of interstellar molecular clouds. We hope this study will be useful to our future understanding about the astrochemistry of formamide and origin of life.