Relative thermodynamic stability of the [C,N,O] linkages as an indication of the most abundant structures in the ISM

Fourré, Isabelle; Matz, Olivier; Ellinger, Y.; Guillemin, Jean‐Claude

doi:10.1051/0004-6361/202037839

Cited by 12 publications

(26 citation statements)

References 64 publications

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“…The first structure can be a direct result of a radical recombination (OH + CH 2 CN) and the latter can be formed through an O-atom interacting with the triple bond of CH 3 CN or its structural isotope, CH 3 NC. The assignment of CH 3 NCO is also supported by a recent study by Fourré et al (2020), in which the relative thermodynamical stability of 40 isotopes of C 2 H 3 NO is compared. The clearly visible peak at m/z = 58 is associated with an elemental composition of C 2 H 4 NO, which is confirmed with a shift to m/z = 60.…”

Section: H 2 O:ch 3 Cnsupporting

confidence: 52%

Photolysis of acetonitrile in a water-rich ice as a source of complex organic molecules: CH₃CN and H₂O:CH₃CN ices

Bulak

Paardekooper

Fedoseev

et al. 2021

A&A

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Context. Many C-, O-, and H-containing complex organic molecules (COMs) have been observed in the interstellar medium (ISM) and their formation has been investigated in laboratory experiments. An increasing number of recent detections of large N-bearing COMs motivates our experimental investigation of their chemical origin. Aims. We investigate the potential role of acetonitrile (CH3CN) as a parent molecule to N-bearing COMs, motivated by its omnipresence in the ISM and structural similarity to another well-known precursor species, CH3OH. The aim of the present work is to characterize the chemical complexity that can result from vacuum UV photolysis of a pure CH3CN ice and a more realistic mixture of H2O:CH3CN. Methods. The CH3CN ice and H2O:CH3CN ice mixtures were UV irradiated at 20 K. Laser desorption post ionization time-of-flight mass spectrometry was used to detect the newly formed COMs in situ. We examined the role of water in the chemistry of interstellar ices through an analysis of two different ratios of H2O:CH3CN (1:1 and 20:1). Results. We find that CH3CN is an excellent precursor to the formation of larger nitrogen-containing COMs, including CH3CH2CN, NCCN/CNCN, and NCCH2CH2CN. During the UV photolysis of H2O:CH3CN ice, the water derivatives play a key role in the formation of molecules with functional groups of: imines, amines, amides, large nitriles, carboxylic acids, and alcohols. We discuss possible formation pathways for molecules recently detected in the ISM.

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Section: H 2 O:ch 3 Cnsupporting

confidence: 52%

Photolysis of acetonitrile in a water-rich ice as a source of complex organic molecules: CH₃CN and H₂O:CH₃CN ices

Bulak

Paardekooper

Fedoseev

et al. 2021

A&A

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“…1). Recent quantum chemical calculations of the stability of C 2 H 3 NO isomers in general reveal that CH 3 NCO is the most stable of these species, followed by HOCH 2 CN (Fourré et al 2020). Therefore, observations of this isomer couple provide information on interstellar reactions involving cyanides (-CN) and isocyanates (-NCO), two important nitrogen-bearing chemical groups, as well as the physical conditions that steer or prohibit this chemistry.…”

Section: Methyl Isocyanate Glycolonitrilementioning

confidence: 99%

“…These new detections serve as additional evidence for a large and diverse reservoir of prebiotic molecules in starand planet-forming regions, which can contribute to the emergence of biomolecules on planetary bodies. Of the C 2 H 3 NO isomers, CH 3 NCO is energetically the most favourable, followed by HOCH 2 CN, which has a higher relative energy of 12.1-18.6 kcal mol −1 (0.5-0.8 eV molecule −1 or 5800-9300 K molecule −1 ), depending on the level of theory used (Fourré et al 2020). In a thermodynamic equilibrium, lower energy or more stable products are favoured, and in such a scenario, CH 3 NCO is expected to be more abundant than HOCH 2 CN by a factor of at least 1 × 10 9 (assuming a temperature of 300 K).…”

Section: Moleculementioning

confidence: 99%

The prebiotic molecular inventory of Serpens SMM1

Ligterink

Ahmadi

Coutens

et al. 2021

A&A

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Aims. Methyl isocyanate (CH3NCO) and glycolonitrile (HOCH2CN) are isomers and prebiotic molecules that are involved in the formation of peptide structures and the nucleobase adenine, respectively. These two species are investigated to study the interstellar chemistry of cyanides (CN) and isocyanates (NCO) and to gain insight into the reservoir of interstellar prebiotic molecules. Methods. ALMA observations of the intermediate-mass Class 0 protostar Serpens SMM1-a and ALMA-PILS data of the low-mass Class 0 protostar IRAS 16293B are used. Spectra are analysed with the CASSIS line analysis software package in order to identify and characterise molecules. Results. CH3NCO, HOCH2CN, and various other molecules are detected towards SMM1-a. HOCH2CN is identified in the PILS data towards IRAS 16293B in a spectrum extracted at a half-beam offset position from the peak continuum. CH3NCO and HOCH2CN are equally abundant in SMM1-a at [X]/[CH3OH] of 5.3 × 10−4 and 6.2 × 10−4, respectively. A comparison between SMM1-a and IRAS 16293B shows that HOCH2CN and HNCO are more abundant in the former source, but CH3NCO abundances do not differ significantly. Data from other sources are used to show that the [CH3NCO]/[HNCO] ratio is similar in all these sources within ~10%. Conclusions. The new detections of CH3NCO and HOCH2CN are additional evidence for a large interstellar reservoir of prebiotic molecules that can contribute to the formation of biomolecules on planets. The equal abundances of these molecules in SMM1-a indicate that their formation is driven by kinetic processes instead of thermodynamic equilibrium, which would drive the chemistry to one product. HOCH2CN is found to be much more abundant in SMM1-a than in IRAS 16293B. From the observational data, it is difficult to indicate a formation pathway for HOCH2CN, but the thermal Strecker-like reaction of CN− with H2CO is a possibility. The similar [CH3NCO]/[HNCO] ratios found in the available sample of studied interstellar sources indicate that these two species are either chemically related or their formation is affected by physical conditions in the same way. Both species likely form early during star formation, presumably via ice mantle reactions taking place in the dark cloud or when ice mantles are being heated in the hot core. The relatively high abundances of HOCH2CN and HNCO in SMM1-a may be explained by a prolonged stage of relatively warm ice mantles, where thermal and energetic processing of HCN in the ice results in the efficient formation of both species.

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“…These new detections serve as additional evidence for a large and diverse reservoir of prebiotic molecules in star-and planet-forming regions, which can contribute to the emergence of biomolecules on planetary bodies. Of the C 2 H 3 NO isomers, CH 3 NCO is en-ergetically the most favorable, followed by HOCH 2 CN, which has a higher relative energy of 12.1 -18.6 kcal mol −1 (0.5 -0.8 eV molecule −1 or 5800 -9300 K molecule −1 ), depending on the level of theory used (Fourré et al 2020). In a thermodynamic equilibrium, lower energy or more stable products are favored and in such a scenario, CH 3 NCO is expected to be more abundant than HOCH 2 CN by a factor of at least 1×10 9 (assuming a temperature of 300 K).…”

Section: Discussionmentioning

confidence: 99%

“…1. Recent quantum chemical calculations of the stability of C 2 H 3 NO isomers in general, also reveal that CH 3 NCO is the most stable species of those, followed by HOCH 2 CN (Fourré et al 2020). Therefore, observations of this isomer couple provide information on interstellar reactions involving cyanides (-CN) and isocyanates (-NCO), two important nitrogen-bearing chemical groups, and the physical conditions that steer or prohibit this chemistry.…”

Section: Introductionmentioning

confidence: 99%

The prebiotic molecular inventory of Serpens SMM1 I. An investigation of the isomers CH$_{3}$NCO and HOCH$_{2}$CN

Ligterink,

Ahmadi,

Coutens

et al. 2020

Preprint

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Aims. Methyl isocyanate (CH 3 NCO) and glycolonitrile (HOCH 2 CN) are isomers and prebiotic molecules that are involved in the formation of peptide structures and the nucleobase adenine, respectively. These two species are investigated to study the interstellar chemistry of cyanides (CN) and isocyanates (NCO) and to gain insight into the reservoir of interstellar prebiotic molecules. Methods. ALMA observations of the intermediate-mass Class 0 protostar Serpens SMM1-a and ALMA-PILS data of the low-mass Class 0 protostar IRAS 16293B are used. Spectra are analysed with the CASSIS line analysis software package in order to identify and characterise molecules. Results. CH 3 NCO, HOCH 2 CN, and various other molecules are detected towards SMM1-a. HOCH 2 CN is identified in the PILS data towards IRAS 16293B in a spectrum extracted at a half-beam offset position from the peak continuum. CH 3 NCO and HOCH 2 CN are equally abundant in SMM1-a at [X]/[CH 3 OH] of 5.3×10 −4 and 6.2×10 −4 , respectively. A comparison between SMM1-a and IRAS 16293B shows that HOCH 2 CN and HNCO are more abundant in the former source, but CH 3 NCO abundances do not differ significantly. Data from other sources are used to show that the [CH 3 NCO]/[HNCO] ratio is similar in all these sources within ∼10%. Conclusions. The new detections of CH 3 NCO and HOCH 2 CN are additional evidence for a large interstellar reservoir of prebiotic molecules that can contribute to the formation of biomolecules on terrestrial planets. The equal abundances of these molecules in SMM1-a indicate that their formation is driven by kinetic processes instead of thermodynamic equilibrium, which would drive the chemistry to one product. HOCH 2 CN is found to be much more abundant in SMM1-a than in IRAS 16293B. From the observational data, it is difficult to indicate a formation pathway for HOCH 2 CN, but the thermal Strecker-like reaction of CN − with H 2 CO is a possibility. The similar [CH 3 NCO]/[HNCO] ratios found in the available sample of studied interstellar sources indicate that these two species either are chemically related or their formation is affected by physical conditions in the same way. Both species likely form early during star-formation, presumably via ice mantle reactions taking place in the dark cloud or when ice mantles are being heated in the hot core. The relatively high abundances of HOCH 2 CN and HNCO in SMM1-a may be explained by a prolonged stage of relatively warm ice mantles, where thermal and energetic processing of HCN in the ice results in the efficient formation of both species.

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Relative thermodynamic stability of the [C,N,O] linkages as an indication of the most abundant structures in the ISM

Cited by 12 publications

References 64 publications

Photolysis of acetonitrile in a water-rich ice as a source of complex organic molecules: CH₃CN and H₂O:CH₃CN ices

Photolysis of acetonitrile in a water-rich ice as a source of complex organic molecules: CH₃CN and H₂O:CH₃CN ices

The prebiotic molecular inventory of Serpens SMM1

The prebiotic molecular inventory of Serpens SMM1 I. An investigation of the isomers CH$_{3}$NCO and HOCH$_{2}$CN

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Relative thermodynamic stability of the [C,N,O] linkages as an indication of the most abundant structures in the ISM

Cited by 12 publications

References 64 publications

Photolysis of acetonitrile in a water-rich ice as a source of complex organic molecules: CH3CN and H2O:CH3CN ices

Photolysis of acetonitrile in a water-rich ice as a source of complex organic molecules: CH3CN and H2O:CH3CN ices

The prebiotic molecular inventory of Serpens SMM1

The prebiotic molecular inventory of Serpens SMM1 I. An investigation of the isomers CH$_{3}$NCO and HOCH$_{2}$CN

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Photolysis of acetonitrile in a water-rich ice as a source of complex organic molecules: CH₃CN and H₂O:CH₃CN ices

Photolysis of acetonitrile in a water-rich ice as a source of complex organic molecules: CH₃CN and H₂O:CH₃CN ices