Formation pathways and detectability of interstellar C₂HNO-bearing molecules

¹ Universidad Autónoma de Chile, Facultad de Ingeniería, Instituto de Ciencias Aplicadas, Núcleo de Astroquímica & Astrofísica Av. Pedro de Valdivia 425 Providencia Santiago, Chile
² Universidad de Chile, Facultad de Ciencias, departamento de química Av. Las Palmeras 3425 Ñuñoa Santiago, Chile
³ Universidad de Chile, Facultad de Ciencias Físicas y Matemáticas, Departamento de Astronomía Camino el Observatorio 1515 Las Condes Santiago, Chile

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it. ; This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 9 September 2025
Accepted: 22 October 2025

Abstract

Aims. We explored N-bearing molecules of the general formula C₂HNO. We provide their spectroscopic constants, structural properties relevant for detection, and reaction pathways to constrain their formation in the interstellar medium.

Methods. We investigated the molecular structures, spectroscopic constants, and the formation pathways for the isomers, and we report them here from ab initio calculations.

Results. Their formation pathways are mainly dominated by the components HCN + CO and HNC + CO → HNCCO for the second and third species, respectively. We identified five distinct families among the 15 isomers we investigated for C₂HNO, in which global stability favors HCOCN (f1), while HNCCO (f6) has a smaller singlet–triplet gap than all the isomers. We also found additional formation pathways for HNCCO (f6) that have not been proposed before. Furthermore, we identified a connection between HCOCN (f1), HCONC (f2), HCNCO (f5), and HNCCO (f6) via proton transfer isomerization. HNCCO (f6) has also been proposed as a precursor to ethanolamine (NH₂CH₂CH₂OH).

Conclusions. This suggests that HNCCO and other isomers we investigated might contribute to the formation of interstellar complex organic molecules and their observed abundances. In particular, we propose that HCONC (f2), c-HCNCO (f4), and HNCCO (f6 conformer) might be observable based on their dipole moments of 2.49, 3.58, and 1.25 Debye, respectively, which are comparable to the dipole moment of the already detected and most stable isomer HCOCN (2.50 Debye).