On the Formation of Vinylamine (C<sub>2</sub>H<sub>3</sub>NH<sub>2</sub>) in Interstellar Ice Analogs
Chaojiang Zhang, Jia Wang, Andrew M. Turner, Joshua H. Marks, Sankhabrata Chandra, Ryan C. Fortenberry, Ralf I. Kaiser
Abstract
Abstract Amines—organic molecules carrying the –NH 2 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 (C 2 H 3 NH 2 ), which was recently detected toward G+0.693–0.027, in interstellar ice analogs composed of acetylene (C 2 H 2 ) and ammonia (NH 3 ) 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 (C 2 H 3 NH 2 ). Quantum chemical computations suggest that both a radical–radical recombination of the amino (NH 2 ) with the vinyl (C 2 H 3 ) radical and a one-step concerted route are feasible pathways to vinylamine (C 2 H 3 NH 2 ). The results present the first documented route to form vinylamine in interstellar ice analogs. This unsaturated amine, which is isovalent to vinylalcohol (C 2 H 3 OH), 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.