[astro-ph.GA] Context. Formamide formation in the Universe has been the subject of debate due to its importance as a precursor to amino acids and RNA. Current studies focus on the gas-phase and icy grain formation routes. However, formamide formation on bare silicate surfaces or hydrated Mg-bearing molecular models remains largely unexplored in environments relevant to protoplanetary disks.
Aims. This study presents a quantum-chemical investigation of formamide formation on an Mg center and a silicate surface. Mg(OH)2⋅H2O and the bare (010) forsterite (Mg2SiO4) surface, used as an analog of a bare dust-grain surface, may promote formamide formation via NH2 addition to H2CO.
Methods. I employed density functional theory (DFT) to study the addition of NH2 to H2CO with an isolated Mg(OH)2⋅H2O molecular model and on the forsterite (010) surface. First, I benchmarked various theoretical methodologies. I then examined the ability of Mg(OH)2⋅H2O and the forsterite (010) surface to promote formamide formation. Finally, for the case with an entrance barrier, I computed unimolecular rate constants and half-lives to assess its kinetic behavior.
Results. Mg(OH)2⋅H2O promotes proton transfer within the NH2-CH22O intermediate via the O-H group coordinated with Mg following NH2 addition to H2CO, whereas on the forsterite, a barrier-less addition pathway is found when NH2 is initially physisorbed close to the formaldehyde center, followed by proton transfer leading to formamide formation.
Conclusions. The Mg-bearing model systems considered here can promote rapid proton transfer following NH2 addition to H2CO. For the Mg(OH)2⋅H2O model, the reaction step from the pre-reactive complex is predicted to occur on nanosecond timescales at temperatures approaching 300 K. The present work provides kinetic data for astrochemical models.
Dario Campisi
Comments: 18 pages, 10 figures. Accepted for publication in Astronomy & Astrophysics
Subjects: Astrophysics of Galaxies (astro-ph.GA); Chemical Physics (physics.chem-ph)
Cite as: arXiv:2611.07172 [astro-ph.GA] (or arXiv:2611.07172v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2611.07172
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Submission history
From: Dario Campisi
[v1] Wed, 4 Nov 2026 21:56:33 UTC (25,844 KB)
https://arxiv.org/abs/2611.07172
Astrobiology, Astrochemistry,
