Atomistic Modeling of Methyl Formate and Glycolaldehyde Formation on Interstellar Dirty Ice Mantles via a "Radical + Ice" Mechanism
Perrero, Jessica (Universitat Autònoma de Barcelona. Departament de Química)
Pantaleone, Stefano (Università degli Studi di Torino. Dipartimento di Chimica)
Ugliengo, Piero (Università degli Studi di Torino. Dipartimento di Chimica)
Rimola Gibert, Albert (Universitat Autònoma de Barcelona. Departament de Química)

Date:	2025
Abstract:	Methylformate (MF) and glycolaldehyde (GA) are two primogenital organic molecules detected in both cold and warm regions of the interstellar medium (ISM). Both gas-phase and grain-surface pathways have been proposed to explain their abundances, yet uncertainties remain, since prevailing grain-surface mechanisms favor the formation of GA over MF, which mismatch observations in different ISM regions. In this work, MF and GA synthetic reactions are atomistically modeled on surfaces containing variable H (Formula presented. ) O and CO percentages (interstellar dirty ices), in which one of the reactants coming from the gas phase reacts with an icy CO, thus adopting the following two-step "radical + ice" mechanism: for MF, OCH (Formula presented. ) + (Formula presented. ) (Formula presented. ) COOCH (Formula presented. ) + H (Formula presented. ) HCOOCH (Formula presented. ); for GA, CH (Formula presented. ) OH + (Formula presented. ) (Formula presented. ) COCH (Formula presented. ) OH + H (Formula presented. ) HCOCH (Formula presented. ) OH. Calculations show that the first step presents an energy barrier (32-38 kJ mol (Formula presented. ) for MF and 17-20 kJ mol (Formula presented. ) for GA), while the second step is nearly barrierless. Although the energetics favor GA formation, the observed abundances are better explained by desorption phenomena rather than reaction barriers are argued. Specifically, the weaker binding energies of MF (16. 8-46. 1 kJ mol (Formula presented. )) than GA (28. 4-90. 2 kJ mol (Formula presented. )) support its higher abundance in the ISM.
Grants:	European Commission 865657 Agencia Estatal de Investigación PID2021-126427NB-I00 Agencia Estatal de Investigación CNS2023-144902
Note:	Altres ajuts: acords transformatius de la UAB
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Published in:	ChemPlusChem, (September 2025) , art. e202500324, ISSN 2192-6506

DOI: 10.1002/cplu.202500324
PMID: 40970323

13 p, 1.8 MB

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