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First Interstellar Detection of Methyl Carbamate: A New Observational Anchor for Glycine Chemistry

First Interstellar Detection of Methyl Carbamate: A New Observational Anchor for Glycine Chemistry

Glycine-the simplest amino acid-has remained undetected in the interstellar medium despite decades of sensitive searches, motivating alternative approaches to constrain its astrochemical origin.

A promising strategy is to investigate the broader C₂H₅O₂N isomer family and identify detectable members that can serve as observational anchors for glycine-related chemistry. Herein, we report the first robust interstellar detection of methyl carbamate toward the hot molecular core G358.93-0.03 MM1 using ALMA 1 mm observations.

Abundances relative to H2 for C2H5O2N isomers as a function of relative energy (∆E). — Abundances relative to H2 for C₂H₅O₂N isomers as a function of relative energy (∆E). Symbols denote measurements toward G358.93 MM1 and G+0.693-0.027, while arrows indicate 3σ upper limits. The red and cyan lines show the abundance trends predicted from the MEP for G358.93 MM1 and G+0.693-0.027, respectively, constructed using representative kinetic temperatures and adopting syn-GA as a reference. For G358.93 MM1, T_kin = 172 K was adopted from CH₃CN (C. L. Brogan et al. 2019), while for G+0.693-0.027, T_kin = 100 K was adopted from S. Zeng et al. (2018). Abundances for G+0.693-0.027 are taken from V. M. Rivilla et al. (2023). Labels indicate MC as methyl carbamate (CH₃OC(O)NH₂), while GC, GA, and AHA represent glycine (NH₂CH₂C(O)OH), glycolamide (HOCH₂C(O)NH₂), and acetohydroxamic acid (CH₃C(O)NHOH), respectively. — astro-ph.GA

Ten unblended rotational transitions are identified, yielding a column density of (4.21±0.84)×10¹⁵cm⁻² and an excitation temperature of 204±10 K. We also searched for other C₂H₅O₂N isomers with available rotational spectroscopic data, including glycine, but none were detected, allowing us to derive upper limits on their column densities. The resulting abundance pattern deviates significantly from the Minimum Energy Principle predictions, highlighting that the C₂H₅O₂N family is shaped primarily by kinetic chemical process rather than thermodynamic equilibrium.

The observed methyl carbamate abundance is consistent with a grain-surface formation scenario involving radical-radical recombination (CH₃O + NH₂CO), further supported by its correlated abundances with its proposed precursors, methanol and formamide, across diverse astrophysical environments.

This detection establishes methyl carbamate as a new observational anchor for glycine chemistry, providing critical constraints on the formation pathways of amino-acid-related molecules in star-forming regions.

Chunguo Duan, Fengwei Xu, Jun Kang, Qian Gou, Xuefang Xu, Laurent Pagani, Jiaxin Du, Xi Chen

Comments: 14 pages, 6 figures, 3 tables, accepted for publication in ApJL
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2605.07159 [astro-ph.GA] (or arXiv:2605.07159v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2605.07159
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Submission history
From: Chunguo Duan
[v1] Fri, 8 May 2026 02:45:14 UTC (15,684 KB)
https://arxiv.org/abs/2605.07159

Astrobiology, Astrochemistry,

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