On the Formation of Vinylamine (C2H3NH2) in Interstellar Ice Analogs

Abstract

Amines—organic molecules carrying the –NH2 moiety—have been recognized as a vital intermediate in the formation of prebiotic molecules such as amino acids and nucleobases. Here we report the formation of vinylamine (C2H3NH2), which was recently detected toward G+0.693–0.027, in interstellar ice analogs composed of acetylene (C2H2) and ammonia (NH3) exposed to energetic electrons. Our experiments mimic cascades of secondary electrons in the tracks of galactic cosmic rays impinging on interstellar ice in molecular clouds. Tunable photoionization reflectron time-of-flight mass spectrometry (PI–Re-TOF–MS), along with isomer-specific assignments, reveals the production of vinylamine (C2H3NH2). Quantum chemical computations suggest that both a radical–radical recombination of the amino (NH2) with the vinyl (C2H3) radical and a one-step concerted route are feasible pathways to vinylamine (C2H3NH2). The results present the first documented route to form vinylamine in interstellar ice analogs. This unsaturated amine, which is isovalent to vinylalcohol (C2H3OH), could be a key precursor for the abiotic synthesis of prebiotic molecules such as amino acids and nucleobases, with implications for the origins-of-life theme.