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Methylamine (CH 3 NH 2 ) and methanimine (CH 2 NH) represent essential building blocks in the formation of amino acids in interstellar and cometary ices. In our study, by exploiting isomer selective detection of the reaction products via photoionization coupled with reflectron time of flight mass spectrometry (Re-TOF-MS), we elucidate the formation of methanimine and ethylenediamine (NH 2 CH 2 CH 2 NH 2 ) in methylamine ices exposed to energetic electrons as a proxy for secondary electrons generated by energetic cosmic rays penetrating interstellar and cometary ices. Interestingly, the two products methanimine and ethylenediamine are isoelectronic to formaldehyde (H 2 CO) and ethylene glycol (HOCH 2 CH 2 OH), respectively. Their formation has been confirmed in interstellar ice analogs consisting of methanol (CH 3 OH) which is ioselectronic to methylamine. Both oxygen-bearing species formed in methanol have been detected in the interstellar medium (ISM), while for methanimine and ethylenediamine only methanimine has been identified so far. In comparison with the methanol ice products and our experimental findings, we predict that ethylenediamine should be detectable in these astronomical sources, where methylamine and methanimine are present.
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Complex Reactive Acids from Methanol and Carbon Dioxide Ice: Glycolic Acid (HOCH 2 COOH) and Carbonic Acid Monomethyl Ester (CH 3 OCOOH)
Abstract The formation of complex organic molecules by simulated secondary electrons generated in the track of galactic cosmic rays was investigated in interstellar ice analogs composed of methanol and carbon dioxide. The processed ices were subjected to temperature-programmed desorption to mimic the transition of a cold molecular cloud to a warmer star-forming region. Reaction products were detected as they sublime using photoionization reflectron time-of-flight mass spectrometry. By employing isotopic labeling, tunable photoionization and computed adiabatic ionization energies isomers of C 2 H 4 O 3 were investigated. Product molecules carbonic acid monomethyl ester (CH 3 OCOOH) and glycolic acid (HOCH 2 COOH) were identified. The abundance of the reactants detected in analog interstellar ices and the low irradiation dose necessary to form these products indicates that these molecules are exemplary candidates for interstellar detection. Molecules sharing a tautomeric relationship with glycolic acid, dihydroxyacetaldehyde ((OH) 2 CCHO), and the enol ethenetriol (HOCHC(OH) 2 ), were not found to form despite ices being subjected to conditions that have successfully produced tautomerization in other ice analog systems.
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- Award ID(s):
- 2103269
- PAR ID:
- 10415831
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 942
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 43
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.3847/1538-4357/ac97e3
