2023ApJ...952..132Z

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.