Front. Astron. Space Sci. Frontiers in Astronomy and Space Sciences Front. Astron. Space Sci. 2296-987X Frontiers Media S.A. 876870 10.3389/fspas.2022.876870 Astronomy and Space Sciences Original Research Molecular Precursors of the RNA-World in Space: New Nitriles in the G+0.693−0.027 Molecular Cloud Rivilla et al. New Nitriles in G+0.693−0.027 Rivilla Víctor M. 1 * Jiménez-Serra Izaskun 1 Martín-Pintado Jesús 1 Colzi Laura 1 Tercero Belén 2 de Vicente Pablo 3 Zeng Shaoshan 4 Martín Sergio 5 6 García de la Concepción Juan 1 Bizzocchi Luca 7 Melosso Mattia 7 8 Rico-Villas Fernando 1 Requena-Torres Miguel A. 9 10 1 Centro de Astrobiología (CSIC-INTA), Madrid, Spain 2 Observatorio Astronómico Nacional (OAN-IGN), Madrid, Spain 3 Observatorio de Yebes (OY-IGN), Guadalajara, Spain 4 Star and Planet Formation Laboratory, Cluster for Pioneering Research, RIKEN, Saitama, Japan 5 European Southern Observatory, ALMA Department of Science, Santiago, Chile 6 Joint ALMA Observatory, Department of Science Operations, Santiago, Chile 7 Department of Chemistry “Giacomo Ciamician”, University of Bologna, Bologna, Italy 8 Scuola Superiore Meridionale, Università di Napoli Federico II, Naples, Italy 9 Department of Astronomy, University of Maryland, College Park, ND, United States 10 Department of Physics, Astronomy and Geosciences, Towson University, Towson, MD, United States

Edited by: André Canosa, UMR6251 Institut de Physique de Rennes (IPR), France

Reviewed by: Audrey Coutens, UMR5277 Institut de recherche en astrophysique et planétologie (IRAP), France

Donghui Quan, Eastern Kentucky University, United States

 *Correspondence: Víctor M. Rivilla, vrivilla@cab.inta-csic.es

This article was submitted to Astrochemistry, a section of the journal Frontiers in Astronomy and Space Sciences

 08 07 2022 2022 9 876870 15 02 2022 02 06 2022 Copyright © 2022 Rivilla, Jiménez-Serra, Martín-Pintado, Colzi, Tercero, de Vicente, Zeng, Martín, García de la Concepción, Bizzocchi, Melosso, Rico-Villas and Requena-Torres. 2022 Rivilla, Jiménez-Serra, Martín-Pintado, Colzi, Tercero, de Vicente, Zeng, Martín, García de la Concepción, Bizzocchi, Melosso, Rico-Villas and Requena-Torres

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Nitriles play a key role as molecular precursors in prebiotic experiments based on the RNA-world scenario for the origin of life. These chemical compounds could have been partially delivered to the young Earth from extraterrestrial objects, stressing the importance of establishing the reservoir of nitriles in the interstellar medium. We report here the detection towards the molecular cloud G+0.693−0.027 of several nitriles, including cyanic acid (HOCN), and three C4H3N isomers (cyanoallene, CH2CCHCN; propargyl cyanide, HCCCH2CN; and cyanopropyne (CH3CCCN), and the tentative detections of cyanoformaldehyde (HCOCN), and glycolonitrile (HOCH2CN). We have also performed the first interstellar search of cyanoacetaldehyde (HCOCH2CN), which was not detected. Based on the derived molecular abundances of the different nitriles in G+0.693−0.027 and other interstellar sources, we have discussed their formation mechanisms in the ISM. We propose that the observed HOCN abundance in G+0.693−0.027 is mainly due to surface chemistry and subsequent shock-induced desorption, while HCOCN might be mainly formed through gas-phase chemistry. In the case of HOCH2CN, several grain-surface routes from abundant precursors could produce it. The derived abundances of the three C4H3N isomers in G+0.693−0.027 are very similar, and also similar to those previously reported in the dark cold cloud TMC-1. This suggests that the three isomers are likely formed through gas-phase chemistry from common precursors, possibly unsaturated hydrocarbons (CH3CCH and CH2CCH2) that react with the cyanide radical (CN). The rich nitrile feedstock found towards G+0.693−0.027 confirms that interstellar chemistry is able to synthesize in space molecular species that could drive the prebiotic chemistry of the RNA-world.

 astrochemistry RNA-world prebiotic chemisitry molecules-ISM molecular clouds Comunidad de Madrid10.13039/100012818 1 Introduction

Life on Earth appeared about 3.8 billion years ago, around 700 Myr after the formation of the planet (Pearce et al., 2018), but we still do not know the mechanisms that made it possible. One of the most supported hypotheses for the origin of life is known as the RNA world (Gilbert 1986), in which RNA could have performed both metabolic and genetic roles. The process by which inert matter generated first the building blocks of RNA, ribonucleotides, and ultimately RNA itself, remains a mystery. Recent laboratory experiments mimicking prebiotic conditions have shown that ribonucleotides could be synthesized starting from simple molecules (e.g. Powner et al., 2009; Patel et al., 2015; Becker et al., 2019). A plausible origin of this prebiotic material is extraterrestrial delivery (Oró 1961; Chyba and Sagan 1992; Cooper et al., 2001) during the heavy bombardment of meteorites and comets that occurred around 3.9 billions ago (Marchi et al., 2014). These basic molecular precursors may have been already formed prior to the formation of the Solar System, in its parental molecular cloud, through the chemistry that takes place in the interstellar medium (ISM). Therefore, the study of the molecular complexity of the ISM can provide us an illustrative view of the chemical reservoir that could have contributed to feed the prebiotic chemistry on the primitive Earth, and could potentially develop similar processes in other places in the Galaxy under favourable Earth-like planetary environments.

In the last decades, and especially in the last years, astrochemistry has shown that interstellar chemistry is able to synthesize building blocks of key biomolecules. Several of the precursors of ribonucleotides spotted by the prebiotic experiments in the laboratory have been detected in the ISM, like cyanoacetylene (HC3N, Turner 1971), cyanamide (NH2CN, Turner et al., 1975), glycolaldehyde (CH2OHCHO, Hollis et al. 2004, urea (NH2CONH2, Belloche et al. 2019), hydroxylamine (NH2OH, Rivilla et al. 2020), and 1,2-ethenediol ((CHOH)2; Rivilla et al. 2022a). Among the key simple molecular precursors required for the RNA world, numerous works have stressed the dominant role of a particular family of compounds, nitriles, which are molecules with the C+N moiety. This simple but highly versatile functional group offers a unique potential to build-up molecular complexity and activate efficiently the formation of ribonucleotides (Powner et al. 2009; Powner and Sutherland 2010; Patel et al. 2015; Mariani et al. 2018; Becker et al. 2019; Menor Salván et al. 2020), and also other key biomolecules such as peptides or nucleobases (Menor-Salván and Marín-Yaseli 2012; Canavelli et al. 2019; Foden et al. 2020).

With the aim of extending our knowledge on the chemistry of nitriles in the ISM, in this work we have searched for more nitriles towards the molecular cloud G+0.693-0.027 (hereafter G+0.693), including some with increasing complexity that have been proposed as important precursors of prebiotic chemistry. This cloud, located in the Sgr B2 region of the center of our Galaxy, is one of the most chemically rich sources in the ISM. Numerous nitrogen-bearing species, including nitriles, have been detected (see Zeng et al., 2018; Rivilla et al., 2019b, 2021b): cyanoacetylene (HC3N), acetonitrile (CH3CN), cyanamide (NH2CN), the cyanomethyl radical (H2CCN), cyanomethanimine (HNCHCN), and the cyanomidyl radical (HNCN). In this work we report the detection of cyanic acid (HOCN), the tentative detections of glycolonitrile (HOCH2CN) and cyanoformaldehyde (HCOCN), and the first interstellar search of cyanoacetaldeyde (HCOCH2CN) in the ISM, for which we provide an abundance upper limit. We have also searched for three unsaturated carbon-chain nitriles, the C4H3N isomers. We report the detection of cyanopropyne (CH3CCCN), and the second detections in the ISM of cyanoallene (CH2CCHCN) and propargyl cyanide (HCCCH2CN), detected previously only towards the TMC-1 dark cloud (Lovas et al. 2006; McGuire et al. 2020; Marcelino et al. 2021). In Section 2 we present the data of the observational survey, in Section 3 we describe the line identification and analysis, and present the results of the line fitting, and in Section 4 we discuss about the interstellar chemistry of the different species and their possible roles in prebiotic chemistry.

 2 Observations

A high sensitivity spectral survey was carried out towards G+0.693. We used both IRAM 30 m telescope (Granada, Spain) and Yebes 40 m telescope (Guadalajara, Spain). The observations were centred at α(J2000.0) = 17 h 47 m 22 s , and δ(J2000.0) = − 28°21′27 ″ . The position switching mode was used in all the observations with the off position located at Δα = − 885″, Δδ = 290” from the source position. During the IRAM 30m observations the dual polarisation receiver EMIR was connected to the fast Fourier transform spectrometers (FFTS), which provided a channel width of 200 kHz. In this work we have used data covering the spectral windows from 71.8 to 116.7 GHz, 124.8–175.5 GHz, and 199.8 − 238.3 GHz. The spectra were smoothed to velocity resolutions of 1.0 − 2.6 km s−1, depending on the frequency. The observations with the Yebes 40 m radiotelescope used the Nanocosmos Q-band (7 mm) HEMT receiver (Tercero et al., 2021). The receiver was connected to 16 FFTS providing a channel width of 38 kHz and a bandwidth of 18.5 GHz per polarisation, covering the frequency range between 31.3 and 50.6 GHz. The spectra were smoothed to a resolution of 251 kHz, corresponding to velocity resolutions of 1.5 − 2.4 km s−1. The noise of the spectra depends on the frequency range, with values in antenna temperature ( T A * ) as low as 1.0 mK, while in some intervals it increases up to 4.0 − 5.0 mK, for the Yebes data, and 1.3 to 2.8 mK (71 − 90 GHz), 1.5 to 5.8 mK (90 − 115 GHz), ∼10 mK (115 − 116 GHz), 3.1 to 6.8 mK (124 − 175 GHz), and 4.5 to 10.6 mK (199 − 238 GHz), for the IRAM 30m data. The line intensity of the spectra was measured in units of T A * as the molecular emission toward G+0.693 is extended over the beam (Requena-Torres et al., 2006, 2008; Zeng et al., 2018, 2020).

 3 Analysis and Results

Figure 1 shows the nitriles analysed in this work, which include four oxygen-bearing nitriles: cyanic acid (HOCN), cyanoformaldehyde (or formyl cyanide, HCOCN), glycolonitrile (or 2-hydroxyacetonitrile, HCOCH2CN), cyanoacetaldehyde (or 3-oxopropanenitrile, HCOCH2CN); and three C4H3N isomers: cyanoallene (or 2,3-butadienenitrile, CH2CCHCN), propargyl cyanide (or 3-butynenitrile, HCCCH2CN), and cyanopropyne (or 2-butynenitrile, CH3CCCN). The identification and fitting of the molecular lines were performed using the SLIM (Spectral Line Identification and Modeling) tool within the MADCUBA package 1 (version 09/11/2021; Martín et al., 2019). SLIM generates synthetic spectra under the assumption of Local Thermodynamic Equilibrium (LTE), using the spectroscopy provided by laboratory experiments assisted by theoretical calculations. Table 1 lists the spectroscopic references of all the molecules analysed. We have used entries from the Cologne Database for Molecular Spectroscopy (CDMS, Endres et al. 2016), which are based on the laboratory works and theoretical calculations indicated in Table 1. Moreover, we implemented into MADCUBA the spectroscopy of HCOCH2CN from Møllendal et al. (2012).

Three-dimensional representation of the oxygen-bearing nitriles (upper panel) and the three C4H3N isomers (lower panel) analysed in this work. White, gray, red, and blue corresponds to hydrogen, carbon, oxygen and nitrogen atoms, respectively.

Spectroscopy of the molecules analysed in this work.

Molecule Catalog Entry Date Line List ref Dipole Moment ref
HOCN CDMS 43510 May 2009 Brünken et al. (2009) Brünken et al. (2009)
HCOCN CDMS 55501 June 2006 Bogey et al. (1995) Császár (1989)
HOCH2CN CDMS 57512 March 2017 Margulès et al. (2017) Margulès et al. (2017)
HCOCH2CN MADCUBA – January 2022 Møllendal et al. (2012) Møllendal et al. (2012)
HCCCH2CN CDMS 65514 September 2020 Demaison et al. (1985) Demaison et al. (1985)
McGuire et al. (2020)
 CH2CCHCN CDMS 65506 March 2006 Bouchy et al. (1973) Bouchy et al. (1973)
Schwahn et al. (1986)
 CH3CCCN CDMS 65503 April 2004 Moïses et al. (1982) Bester et al. (1984)
Bester et al. (1983)

The molecular catalog, number and date of the entry, and the references for the line lists and dipole moments are listed.

To evaluate if the molecular transitions of interest are blended with emission from other species, we have also considered the LTE model that includes the total contribution of all the species that have been identified so far towards G+0.693 (e.g., Requena-Torres et al., 2008; Zeng et al., 2018; Rivilla et al., 2019a, 2020; Jiménez-Serra et al., 2020; Rivilla et al., 2021a,b; Zeng et al., 2021; Rodríguez-Almeida et al., 2021a,b; Rivilla et al., 2022a,b). To derive the physical parameters of the molecular emission, we used the AUTOFIT tool of SLIM, which finds the best agreement between the observed spectra and the predicted LTE model, and provides the best solution for the parameters, and their associated uncertainties (see details of the formalism used in Martín et al., 2019). The free parameters of the model are: molecular column density (N), excitation temperature (T ex), linewidth (or full width at half maximum, FWHM), and velocity (v LSR). We have left these four parameters free whenever possible, providing their associated uncertainties. For the cases in which the algorithm used by AUTOFIT does not converge, we have fixed some of them to allow the algorithm to converge. In the following, we present the analysis of the different molecules studied. For each species, we have applied AUTOFIT using unblended transitions and transitions that, while partially blended with other species already identified in G+0.693, properly reproduces the observed spectra. We note that for all molecules the transitions that are not shown are consistent with the observed spectra, but they are heavily blended with lines from other molecular species or they are too weak to be detected, according to the line intensities predicted by the LTE model.

3.1 Oxygen-Bearing Nitriles 3.1.1 Cyanic Acid (HOCN) and Cyanoformaldehyde (HCOCN)

HOCN was already reported towards G+0.693 by Brünken et al. (2010) (their source Sgr B2 (20,100) 2 ), and also by Zeng et al. (2018) using in both cases less sensitive observations. We provide here a new analysis using deeper observations. We have detected six transitions of this species that are completely unblended, which are shown in Figure 2, and listed in Table 2. These transitions include the three transitions identified by Zeng et al. (2018), the confirmation of the 80,8 − 70,7 transition tentatively detected in that work (see their Figure B15), and two new transitions (Table 2). The best LTE fit derived by MADCUBA, where all parameters were left free, is shown in Figure 2, and the derived physical parameters are presented in Table 4. We obtained a column density of (2.13 ± 0.04 × 10 13 cm−2 (Table 4), which translates into a molecular abundance with respect to molecular hydrogen of 1.6 × 10−10, using N(H2) = 1.35 × 1023 cm−2 from Martín et al. (2008). The results are consistent, within the uncertainties, with those derived by Zeng et al. (2018).

Selected cyanic acid (HOCN) transitions (see Table 2) detected towards the G+0.693 molecular cloud. The best LTE fit derived with MADCUBA for the HOCN emission is shown with a red curve, while the blue curve shows the total emission considering all the species identified towards this molecular cloud. The y-axis shows the line intensity in antenna temperature scale ( T A * ) in Kelvin, and the x-axis shows the frequency in GHz.

List of detected transitions of the oxygen-bearing nitriles analysed in this work. We indicate the frequency, quantum numbers, logarithm of the Einstein coefficient (A ul), energy of the upper levels of each transition (Eu), and information about the possible blending by other identified or unidentified (U) species towards G +0.693.

Molecule Frequency (GHz) Transition J K a , K c logA ul (s−1) Eu (K) Blending
HOCN 41.9508371 20,2 − 10,1 −5.3239 3.0 unblended
HOCN 83.5383960 41,4 − 31,3 −4.4087 42.2 blended with U
HOCN 83.9005702 a 40,4 − 30,3 −4.3750 10.1 unblended
HOCN 84.2524547 41,3 − 31,2 −4.3976 42.3 blended with HCCCH2CN
HOCN 104.8746777 a 50,5 − 40,4 −4.0746 15.1 unblended
HOCN 125.8480951 60,6 − 50,5 −3.8304 21.1 unblended
HOCN 146.8206846 a 70,7 − 60,6 −3.6248 28.1 unblended
HOCN 167.7923140 b 80,8 − 70,7 −3.4472 36.2 unblended
HCOCN 72.1192555 11,1 − 00,0 −5.0767 3.5 blended
HCOCN 81.433113 21,2 − 10,1 −4.9642 4.4 blended with NH2CH2CH2OH
HCOCN 90.5710141 31,3 − 20,2 −4.8461 5.7 unblended
HCOCN 99.5348108 41,4 − 30,3 −4.7342 7.6 unblended
HCOCN 108.3274964 51,5 − 40,4 −4.6301 9.8 part. blended with HCCO and U
HCOCN 207.3132961 22,0 − 11,1 −3.7478 13.4 blended with U
HOCH2CN 35.934379 41,4 − 31,3 −5.8654 5.7 unblended
HOCH2CN 37.781601 41,3 − 31,2 −5.8001 5.9 blended with c-C2H4O and U
HOCH2CN 44.907438 51,5 − 41,4 −5.5549 7.9 blended with t − HCOOH
HOCH2CN 45.975528 50,5 − 40,4 −5.5069 6.6 unblended
HOCH2CN 75.463333 81,7 − 71,6 −4.8528 17.7 blended with s-C2H5CHO

Transition detected in Zeng et al. (2018).

Transition tentatively detected in Zeng et al. (2018).

We also report here the first tentative detection of HCOCN towards G+0.693. Figure 3 shows that the 31,3 − 20,2 (90.5710141 GHz) and 41,4 − 30,3 (99.5348108 GHz) transitions are unblended, while other transitions are partially blended with other species (Table 2). To perform the fit, we fixed T ex, FWHM, and v LSR to the ones derived from HOCN. We obtained a column density of (0.76 ± 0.11 × 10 13 cm−2, almost one order of magnitude lower than the upper limit reported by Zeng et al. (2018) of < 6 × 10 13 cm−2 towards G+0.693. The derived molecular abundance is 6 × 10−11, which is very similar to that found in the TMC-1 dark cloud by Cernicharo et al. (2021). The HOCN/HCOCN ratio is ∼2.8.

Selected cyanoformaldehyde (HCOCN) transitions (see Table 2) detected towards the G+0.693 molecular cloud. The best LTE fit derived with MADCUBA for the HCOCN emission is shown with a red curve, while the blue curve shows the total emission considering all the species identified towards this molecular cloud. The y-axis shows the line intensity in antenna temperature scale ( T A * ) in Kelvin, and the x-axis shows the frequency in GHz.

 3.1.2 Glycolonitrile (HOCH<sub>2</sub>CN)

This species is also tentatively detected towards G+0.693. We show in Figure 4 two molecular transitions of HOCH2CN that are unblended (Table 2), and those partially blended with other species already identified in this cloud. To perform the fit, we fixed T ex and FWHM to the ones derived for HOCN, and used v LSR = 67 km s−1, which best reproduces the velocity of the two unblended transitions. We obtained a column density of (0.8 ± 0.2 × 10 13 cm−2 (Table 4), and a molecular abundance of 6 × 10−11, very similar to that of HOCN.

Selected transitions of glycolonitrile (HOCH2CN; see Table 2) detected towards the G+0.693 molecular cloud. The best LTE fit derived with MADCUBA for the HOCH2CN emission is shown with a red curve, while the blue curve shows the total emission considering all the species identified towards this molecular cloud. The y-axis shows the line intensity in antenna temperature scale ( T A * ) in Kelvin, and the x-axis shows the frequency in GHz.

 3.1.3 Cyanoacetaldehyde (HCOCH<sub>2</sub>CN)

This molecule is not currently included in any of the commonly used molecular databases such as CDMS or the Jet Propulsion Laboratory catalog (JPL; Pickett et al., 1998). The conformational energy landscape of HCOCH2CN and the effects of the large amplitude motions on its rotational spectrum have been described in detail by Møllendal et al. (2012). We have used the spectroscopic information provided in this work to implement it into MADCUBA. The most stable rotamer (referred to as species I in the cited reference) possesses two equivalent positions in the electronic energy potential function for rotation about its C1–C2 bond (see Figure 1 of Møllendal et al., 2012). They are separated by a barrier of 0.84 kJ mol−1 (computed at MP2 level) at the exact antiperiplanar conformation. Large amplitude vibrations and tunneling for the torsion about the C1–C2 bond leads to the existence of two closely spaced energy levels for the ground state labelled with a plus sign (+) for the lowest-energy level and with a minus sign (−) for the higher-energy level. These two states are separated by an energy difference ΔE/h of ∼58.8 GHz. For the present spectral calculation we have reanalysed the rotational transitions reported by Møllendal et al. (2012) using the same set of spectroscopic parameters employed in their fit 1 (see their Table 4). The rest-frequencies have then been computed in the J = 0–70 interval with K a max = 50. Theoretical values of dipole moments μ a = 0.932 D, μ b = 1.574 D, and μ c = 1.274 D, computed at CCSD level (Møllendal et al., 2012) have been employed. All the calculations have been performed with the CALPGM suite of programs Pickett (1991).

This species is not detected towards G+0.693. We have derived an upper limit for its abundance using the brightest transition according to the LTE model that are unblended, namely the 62,5–51,4 transition at 101.598576 GHz. MADCUBA calculates the upper limit of the column density using the 3σ value of the integrated intensity (see details in Martín et al., 2019). We have used the same T ex, FWHM, and v LSR used for HOCH2CN. We obtained an upper limit of the HCOCH2CN abundance of < 2.7 × 10 − 10 (Table 4).

 3.2 C<sub>4</sub>H<sub>3</sub>N Isomers

We report in this section the first detection towards G+0.693 of cyanoallene (CH2CCHCN), propargyl cyanide (HCCCH2CN), and cyanopropyne (CH3CCCN).

3.2.1 Cyanoallene (CH<sub>2</sub>CCHCN)

Figure 5 shows the molecular transitions of CH2CCHCN that are unblended, or only slightly blended with other species already identified in this source, whose spectroscopic information is presented in Table 3. The G+0.693 cloud is the second interstellar source where CH2CCHCN has been detected, after the cold cloud TMC-1 (Lovas et al., 2006; Marcelino et al., 2021). We left N, T ex , FWHM, and v LSR as free parameters, and obtained a column density of (2.34 ± 0.06 × 10 13 cm−2, and a molecular abundance of 1.7 × 10−10 (Table 4).

Selected transitions of cyanoallene (CH2CCHCN; see Table 3) detected towards the G+0.693 molecular cloud. The best LTE fit derived with MADCUBA for the CH2CCHCN emission is shown with a red curve, while the blue curve shows the total emission considering all the species identified towards this molecular cloud. The y-axis shows the line intensity in antenna temperature scale ( T A * ) in Kelvin, and the x-axis shows the frequency in GHz.

List of observed transitions of the C4H3N isomers analysed in this work. We indicate the frequency, quantum numbers, Einstein coefficient (A ul), energy of the upper levels of each transition (Eu), and information about the possible blending by other identified or unidentified (U) species towards G +0.693.

Molecule Frequency (GHz) Transition a logA ul (s−1) Eu (K) Blending
CH2CCHCN 31.6156000 61,5 − 51,4 −5.5633 6.4 blended with aGg′-(CH2OH)2
CH2CCHCN 35.3790500 71,7 − 61,6 −5.4086 7.9 blended with CH3COCH3
CH2CCHCN 36.0646889 70,7 − 60,6 −5.3748 6.9 unblended
CH2CCHCN 36.1402200 72,6 − 62,5 −5.4089 11.4 unblended
CH2CCHCN 36.2225000 72,5 − 62,4 −5.4059 11.4 unblended
CH2CCHCN 36.8784700 71,6 − 61,5 −5.3546 8.2 blended with U
CH2CCHCN 40.4257132 81,8 − 71,7 −5.2292 9.9 unblended
CH2CCHCN 41.1870836 80,8 − 70,7 −5.1981 8.9 unblended
CH2CCHCN 41.2976561 82,7 − 72,6 −5.2225 13.4 unblended
CH2CCHCN 41.4207138 82,6 − 72,5 −5.2187 13.4 unblended
CH2CCHCN 42.1384521 81,7 − 71,6 −5.1751 10.2 blended with c-C3H2
CH2CCHCN 45.4695206 91,9 − 81,8 −5.0716 12.0 blended with CH3NHCHO
CH2CCHCN 46.2978836 90,9 − 80,8 −5.0429 11.1 unblended
CH2CCHCN 46.4528399 92,8 − 82,7 −5.0603 15.6 blended with CH3CONH2
CH2CCHCN 46.6280696 92,7 − 82,6 −5.0555 15.7 blended with HC2CHO
CH2CCHCN 47.3948488 91,8 − 81,7 −5.0176 12.5 unblended
CH2CCHCN 75.6463060 73,4 − 82,7 −6.2551 17.0 blended with U
CH2CCHCN 75.6587572 151,15 − 141,14 −4.3956 30.2 blended with U
CH2CCHCN 76.6665519 150,15 − 140,14 −4.3767 29.6 blended with C2H5OH
CH2CCHCN 78.0996741 152,13 − 142,12 −4.3600 34.4 blended with U
CH2CCHCN 78.8285795 151,14 − 141,13 −4.3421 31.4 blended with CH3COOH
CH2CCHCN 81.674936 160,16 − 150,15 −4.2935 33.5 blended with C2H5OH
CH2CCHCN 84.0442448 161,15 − 151,14 −4.2576 35.5 unblended
HCCCH2CN 31.8489874 61,6 − 51,5 −5.2773 6.2 unblended
HCCCH2CN 33.8637212 61,5 − 51,4 −5.1974 6.5 unblended
HCCCH2CN 37.1392132 71,7 − 61,6 −5.0691 8.0 unblended
HCCCH2CN 38.1027037 70,7 − 60,6 −5.0271 7.3 unblended
HCCCH2CN 38.3423461 72,6 − 62,5 −5.0555 10.6 unblended
HCCCH2CN 38.6167091 72,5 − 62,4 −5.0461 10.7 unblended
HCCCH2CN 39.4865865 71,6 − 61,5 −4.9892 8.4 unblended
HCCCH2CN 42.0111351 51,5 − 40,4 −5.4001 4.6 blended with n-C3H7CN
HCCCH2CN 42.4217854 81,8 − 71,7 −4.8900 10.0 unblended
HCCCH2CN 43.8024266 82,7 − 72,6 −4.8695 12.7 blended with HNCO
HCCCH2CN 44.2102030 82,6 − 72,5 −4.8574 12.8 unblended
HCCCH2CN 45.0990808 81,7 − 71,6 −4.8103 10.6 unblended
CH3C3N 33.0513004 81 − 71 −5.3573 14.6 unblended
CH3C3N 33.0516190 80 − 70 −5.3505 7.1
CH3C3N 37.1826557 91 − 81 −5.1995 16.4 blended with CH3OCHO
CH3C3N 37.1830142 90 − 80 −5.1942 8.9
CH3C3N 41.3139909 101 − 91 −5.0590 18.4 blended with aGg′-(CH2OH)2
CH3C3N 41.3143891 100 − 90 −5.0546 10.9
CH3C3N 45.4453036 111 − 101 −4.9321 20.6 unblended
CH3C3N 45.4457416 110 − 100 −4.9286 13.1
CH3C3N 49.5765916 121 − 111 −4.8166 23.0 unblended
CH3C3N 49.5770694 120 − 110 −4.8136 15.5
CH3C3N 74.3636580 181 − 171 −4.2809 41.4 unblended
CH3C3N 74.3643850 180 − 170 −4.2795 33.9
CH3C3N 82.6257600 201 − 191 −4.1422 49.1 blended with s-C2H5CHO
CH3C3N 82.6265180 200 − 190 −4.1411 41.6
CH3C3N 86.756698 211 − 201 −4.0780 53.3 blended with H13CO+
CH3C3N 86.757524 210 − 200 −4.0770 45.8
CH3C3N 90.8876208 221 − 211 −4.0169 57.7 blended with CH3COCH3
CH3C3N 90.8884956 220 − 210 −4.0159 50.2
CH3C3N 95.0184892 231 − 221 −3.9584 62.2 unblended
CH3C3N 95.0194037 230 − 220 −3.9576 54.7
CH3C3N 99.1493060 241 − 231 −3.9026 67.0 unblended
CH3C3N 99.1502601 240 − 230 −3.9017 59.5
CH3C3N 103.280069 251 − 241 −3.8490 71.9 unblended
CH3C3N 103.2810626 250 − 240 −3.8482 64.4
CH3C3N 107.4107758 261 − 251 −3.7975 77.1 blended with CH3CONH2
CH3C3N 107.4118089 260 − 250 −3.7968 69.6

The format of the quantum numbers is J K a , K c for HCCCH2CN and CH2CCHCN (asymmetric rotors), and J K for CH3C3N (symmetric top molecule).

Derived physical parameters of the nitriles towards G+0.693 analysed in this work using MADCUBA, along with their associated uncertainties. The fixed parameters used in the fit are shown without associated uncertainties (see text).

Molecule N a ( × 1013 cm−2) T ex (K) vLSR (km s−1) FWHM (km s−1) Abundance b (×10−10)
HOCN 2.13±0.04 7.4±0.2 68.0±0.2 19.2±0.3 1.6
HCOCN 0.76±0.11 7.4 68 19.2 0.6
HOCH2CN 0.8±0.2 7.4 67 19.2 0.6
HCOCH2CN < 3.6 7.4 67 19.2 < 2.7
CH2CCHCN 2.34±0.06 12.1±0.5 66.1±0.3 21.3±0.7 1.7
HCCCH2CN 1.77±0.08 12.1 67.0±0.6 21.3 1.3
CH3CCCN 1.35±0.03 18.6±1.0 68 21.3 1.0

The uncertainties of the column densities are derived by the AUTOFIT algorithm implemented in MADCUBA (see Martín et al., 2019 for details), and do not contain calibrations errors, which are expected to be ∼ 10 % .

We adopted N(H2) = 1.35 × 1023 cm−2, from Martín et al. (2008).

 3.2.2 Propargyl Cyanide (HCCCH<sub>2</sub>CN)

Figure 6 shows the molecular transitions of HCCCH2CN that are unblended, or only slightly blended with other species already identified in this cloud, whose spectroscopic information is presented in Table 3. As in the case of its isomer CH2CCHCN, G+0.693 is the second interstellar source where HCCCH2CN has been detected, after the cold cloud TMC-1 (McGuire et al., 2020; Marcelino et al., 2021). We fixed T ex and FWHM to the values obtained for CH2CCHCN, and left N and v LSR free. We obtained a column density of (1.77 ± 0.08 × 10 13 cm−2, and a molecular abundance of 1.3 × 10−10. The CH2CCHCN/HCCCH2CN ratio is ∼ 1.3.

Selected transitions of propargyl cyanide (HCCCH2CN; see Table 3) detected towards the G+0.693 molecular cloud. The best LTE fit derived with MADCUBA for the HCCCH2CN emission is shown with a red curve, while the blue curve shows the total emission considering all the species identified towards this molecular cloud. The y-axis shows the line intensity in antenna temperature scale ( T A * ) in Kelvin, and the x-axis shows the frequency in GHz.

 3.2.3 Cyanopropyne (CH<sub>3</sub>CCCN)

Figure 7 shows the spectra of multiple unblended or slightly blended transitions of CH3CCCN (listed in Table 3). Unlike its isomers, which are asymmetric molecules, CH3CCCN is a symmetric top molecule. For the analysis, we have used the lowest energy K = 0 and K = 1 transitions (see Table 3), which are the ones that dominate the line emission in a source with low T ex like G+0.693 (5 − 20 K; see e.g. Zeng et al., 2018). We fixed the FWHM and v LSR to the values derived for CH2CCHCN, leaving N and T ex as free parameters. We obtained a column density of (1.35 ± 0.03 × 10 13 cm−2 (Table 4), and a molecular abundance of 1.0 × 10−10. The isomeric ratios of CH2CCHCN/CH3CCCN and HCCCH2CN/CH3CCCN are ∼1.8 and ∼1.3, respectively.

Selected transitions of cyanopropyne (CH3CCCN; see Table 3) detected towards the G+0.693 molecular cloud. The best LTE fit derived with MADCUBA for the CH3CCCN emission is shown with a red curve, while the blue curve shows the total emission considering all the species identified towards this molecular cloud. The y-axis shows the line intensity in antenna temperature scale ( T A * ) in Kelvin, and the x-axis shows the frequency in GHz.

 4 Discussion 4.1 Interstellar Chemistry 4.1.1 Oxygen-Bearing Nitriles

We show in Figure 8 the molecular abundances of the O-bearing nitriles detected towards G+0.693 studied in this work. The relative ratio of the detected species HOCN:HCOCN:HOCH2CN is 2.8:1:1. By extrapolating the hydroxy/aldehyde (OH/HCO) ratio of HOCN/HCOCN to HOCH2CN/HCOCH2CN, one should expect an abundance of 0.15 × 10−10 for HCOCH2CN, more than one order of magnitude lower than the upper limit derived from current observations ( < 2.7 × 10 − 10 , see Table 4). This suggests that deeper observations reaching higher sensitivity will be needed to address the detection of this species.

Molecular abundances with respect to H2 of the oxygen-bearing nitriles studied in this work derived in different interstellar sources. Purple bars correspond to G+0.693 (this work; see Table 4), with the HCOCH2CN value indicating an upper limit. We compare with other sources: several positions also in the Sgr B2 region (magenta; Brünken et al., 2010, see also Marcelino et al., 2010); several dense cores (B1-b, L1544, L183, and L483) and the lukewarm corino L1527 (green: Marcelino et al., 2010; Marcelino et al., 2018); the dark cloud TMC-1 (yellow; Cernicharo et al., 2021); and the IRAS 16293–2422 B hot corino (red, Zeng et al., 2019). To derive the uncertainties of the molecular abundances we have considered the uncertainties of the molecular column densities reported in the different works, or a 15% of the value of N if the uncertainty is not provided, and we assumed an uncertainty for the N(H2) column densities of 15%.

In the following, we discuss possible formation routes of the different O-bearing nitriles, combining the results obtained in G+0.693 and in other interstellar sources with theoretical and experimental works:

• HOCN: besides G+0.693, this species was detected previously towards several other positions of the Sgr B2 region in the Galactic Center (Brünken et al., 2009; Brünken et al., 2010), and towards several dense cores (B1-b, L1544, L183, and L483) as well as the lukewarm corino L1527 (Marcelino et al., 2010; Marcelino et al., 2018). Figure 8 shows that the HOCN abundance derived in G+0.693 is of the same order of magnitude of those detected in other Sgr B2 positions ( ∼ 10 − 11 − 10 − 10 ; Brünken et al., 2010), and higher than those derived in the dense cores and L1527 (Marcelino et al., 2018). This suggests that the role of surface-chemistry and the presence of shocks enhance the HOCN abundance, similarly to its isomer HNCO (Hasegawa and Herbst 1993; Garrod et al., 2008; Martín et al., 2008; Rodríguez-Fernández et al., 2010; Quénard et al., 2018). The chemistry of the molecular clouds of the Galactic Center, and that of G+0.693 in particular, is dominated by large-scale shocks (Martín-Pintado et al., 2001; Martín et al., 2008), which are responsible for the sputtering of dust grains, releasing many molecules formed on the grain surfaces into the gas phase (see Caselli et al., 1997; Jiménez-Serra et al., 2008). This can increase the abundance of the species by orders of magnitude. Similarly to isomer HNCO, which is efficiently formed on grain surfaces by hydrogenation of accreted OCN (Hasegawa and Herbst 1993; Garrod et al., 2008), HOCN can also be formed on grain mantles if the oxygen atom is hydrogenated: O C N + H → H O C N ,

and then subsequently released by shocks (Brünken et al., 2010). An alternative surface route might be the reaction of two highly abundant species: C N + O H → H O C N

• HCOCN: this species has been detected previously in the massive hot core SgrB2 (N) (Remijan et al., 2008), and in the dark cloud TMC-1 (Cernicharo et al., 2021). The HCOCN abundances found in G+0.693 and TMC-1 are very similar, in the range of (3.5 − 5 × 10 − 11 , as shown in Figure 8. These two regions have very different physical conditions, which imprint their chemistry. While in the case of the dark and cold TMC-1 cloud gas-phase chemistry is thought to be dominant, since thermal or shock-induced desorptions are highly unlikely, the chemistry of G+0.693 is strongly affected by shocks, and thus surface chemistry also plays an important role. Therefore, the similar HCOCN abundances in G+0.693 and TMC-1 points towards a predominant gas-phase chemistry origin. Indeed, the quantum chemical calculations by Tonolo et al. (2020) have shown that HCOCN species can be efficiently formed through the gas-phase reaction between formaldehyde (H2CO) and the cyanide radical (CN), which are highly abundant species in the ISM, in which the CN radical attacks the unsaturated carbon of H2CO and substitutes one of the H atoms: H 2 C O + C N → H C O C N + H ,

• HOCH2CN: this species was first detected in the ISM towards the hot corino IRAS 16293–2422 B (Zeng et al., 2019), and more recently towards the SMM1 hot corino in Serpens (Ligterink et al., 2021). The abundance derived in G+0.693 is 4.3 × 10−10, very similar to that derived in the hot component of IRAS 16293–2422 B (Figure 8). The chemical model by Zeng et al. (2019) considered the surface formation route proposed by the laboratory experiments of Danger et al. (2012); Danger et al. (2013): H 2 C O + H C N → H O C H 2 C N

and ion-neutral destruction reactions with H 3 + , HCO+, and H3O+, and concluded that more chemical pathways are needed to explain the abundance observed in the hot corino IRAS 16293–2422 B. More recently, the quantum chemical cluster calculations performed by Woon (2021) have proposed new surface reactions between C+, which is distributed throughout the whole Galactic Center (Harris et al., 2021), and two very abundant species, HCN and HNC (e.g. Colzi et al. 2022), embedded in H2O icy grain mantles. The C+ ion reacts with HCN and HNC forming intermediate species that attacks neighboring H2O molecules of the ices, resulting into the radicals HOCHNC and HOCHCN. These species can be easily hydrogenated on the grain surfaces to form HOCH2CN. The inclusion of these alternative surface routes in the chemical models might help to explain the HOCH2CN abundances detected in G+0.693 and hot corinos, where the molecules can be injected to the gas phase through shocks and thermal effects, respectively.

• HCOCH2CN: the theoretical calculations performed by Horn et al. (2008) proposed that this species might be formed from two abundant precursors in the ISM: H C 3 N + H 2 O → H C O C H 2 C N

However, while this reaction might occur in aqueous solution, its activation energy, 216 kJ mol−1 (25,980 K), is too high to occur in the ISM. Recently, Alessandrini and Melosso (2021) have studied the reaction between oxirane (or ethylene oxide, c − C2H4O) − also detected towards G+0.693 (Requena-Torres et al., 2008) − and the CN radical. Although the main pathway is the H abstraction from oxirane, forming the oxiranyl radical, the formation of HCOCH2CN + H is also possible with a rate of ∼ 10 − 12 cm3 molec−1 s−1. New theoretical and/or experimental works of this species are needed to determine if it can be efficiently formed in the ISM, opening the possibility for its interstellar detection.

 4.1.2 C<sub>4</sub>H<sub>3</sub>N Isomers

The unsaturated C4H3N isomers towards G+0.693 have very similar abundances within a factor of 2, spanning a range of (1.0 − 1.7 × 10 − 10 (Table 4), as also previously observed in the dark cloud TMC-1 by Marcelino et al. (2021). Moreover, Figure 9 shows that the abundances in these two molecular clouds, which have very different physical conditions, as mentioned above, are very similar. This suggests that these molecules are predominantly formed through gas-phase chemistry (see previous discussion about HCOCN). Furthermore, since the three isomers are almost equally abundant, their respective formation might be linked to common precursors. Indeed, Balucani et al. (2000) proposed that these unsaturated nitriles can be formed efficiently by reactions in which the cyanide radical (CN) attacks an unsaturated carbon of the hydrocarbons methylacetylene (CH3CCH) and allene (CH2CCH2): C H 3 C C H + C N → 0.22 / 0.50 C H 3 C C C N + H , → 0.0 / 0.50 C H 2 C C H C N + H , C H 2 C C H 2 + C N → 0.90 C H 2 C C H C N + H , → 0.10 H C C C H 2 C N + H ;

Upper panel: Abundances with respect to H2 of the C3H4N isomers detected towards G+0.693 (purple; this work) and TMC-1 (yellow, Marcelino et al., 2021). To derive the uncertainties of the molecular abundances we have considered the uncertainties of the molecular column densities of the C3H4N isomers reported in this work (Table 4) and in Marcelino et al. 2021, and we assumed an uncertainty for the N(H2) column density of 15%. Lower panel: Molecular ratios between the abundances of the C3H4N isomers in G+0.693 and TMC-1.

in which the branching ratios for each reaction are indicated above each arrow (normalized to 1). These ratios were derived using the experiments and quantum chemical calculations by Abeysekera et al. (2015)/Balucani et al. (2000) in the first two reactions, and from Balucani et al. (2002) in the latter two reactions. These radical-neutral reactions show no entrance barriers, they have exit barriers well below the energy of the reactant molecules, and are exothermic. The proposed precursors CN and CH3CCH are abundant molecules in the ISM. In particular, they were detected towards G+0.693 with molecular abundances of 1.5 × 10−8 and 1.3 × 10−8, respectively (Rivilla et al., 2019a; Bizzocchi et al., 2020), so they are viable precursors. Allene (CH2CCH2) has zero dipole moment, so its detection through rotational spectroscopy is not possible, and thus its abundance is unknown. However, the similar abundances of the three isomers suggest that it can be as abundant as CH3CCH in the ISM.

Regardless of the actual abundance of CH2CCH2, which is unknown, the proposed branching ratios seem to be in conflict with the observational findings in G+0.693 and TMC-1, since they are not able to produce equal abundance for the three isomers. As already noted by Marcelino et al. (2021), it would be interesting to study the branching ratios of the CH2CHCH2 + CN reaction using the chirped-pulse uniform flow experiment used by Abeysekera et al. (2015) for the CH2CCH + CN reaction, and compare them with the values derived from quantum chemical calculations by Balucani et al. (2002), to reconcile the experimental/theoretical works with the findings of the observations.

 5 Conclusion: Implications for the RNA-World

Compounds of the nitrile family, under early Earth conditions, offer a rich chemistry due to the large number of reactions that they can trigger. Nitriles could be transformed into amides, carboxylic acids and esters via hydrolysis and alcoholysis respectively. Autocondensation of nitriles in a basic environment could yield to cyanoketones and cyanoenamines, a high reactive intermediate in the synthesis of complex five- and six-member heterocycles (Erian 1993). The high amounts of ammonia of the reducing atmosphere of the primitive Earth is a favorable scenario to obtain amidines from nitriles (Shriner and Neumann 1944). Moreover, the NCN backbone of amidines offer an unique structure to yield complex N-containing heterocycles like purine and pyrimidine nucleobases. Furthermore, nitriles can activate the formation of the building blocks of RNA, ribonucleotides (e.g. Powner et al., 2009; Powner and Sutherland 2010; Patel et al., 2015). Two of the nitriles studied in this work, i.e. glycolonitrile and cyanoacetaldehyde, have been proposed as activation agents for the formation of more complex molecules with prebiotic relevance. The latter (HCOCH2CN) is a precursor of cytosine (Robertson and Miller 1995; Nelson et al., 2001; Menor-Salván et al., 2009). The former (HOCH2CN) is not only a fundamental precursor to ribonucleotides and lipids (Ritson and Sutherland 2012, 2013; Patel et al. 2015; Liu et al. 2018; Ritson et al. 2018), but also of other biologically-important molecules such as the simplest amino acid glycine (NH2CH2COOH; Rodriguez et al., 2019), and of the nucleobase adenine through rapid HCN oligomerisation (Schwartz and Goverde 1982; Menor-Salván and Marín-Yaseli 2012). Unsaturated carbon-chain nitriles like the C4H3N isomers studied in this work are also especially interesting for prebiotic chemistry because the presence of unsaturated bonds allows further chemical evolution that can produce biomolecules (Rosi et al. 2018).

This work extends the repertoire of nitriles detected in the G+0.693 molecular cloud, a region that exhibits one of the richest chemical content in the ISM, and hence it is a well suited testbed to census the molecular species present in the ISM. Besides HOCN, already reported by Brünken et al. (2010) and Zeng et al. (2018), we have provided the tentative detections towards this source of HCOCN and HOCH2CN (third detection in the ISM), and the detection of the three unsaturated C4H3N isomers (being the second source after TMC-1 in which all three isomers are identified). These detections confirm the rich reservoir of nitriles in space, and complete the list of prebiotic molecular precursors detected previously, including species directly involved in the synthesis of ribonucleotides such as glycolaldehyde (HCOCH2OH; Hollis et al., 2004; Requena-Torres et al., 2006; Beltrán et al., 2009; Jørgensen et al., 2012), urea (Belloche et al., 2019; Jiménez-Serra et al., 2020), hydroxylamine NH2OH (Rivilla et al., 2020), and 1,2-ethenediol (Rivilla et al. 2022a); of amino acids, such as amino acetonitrile (NH2CH2CN; Belloche et al., 2008; Melosso et al., 2020); and of lipids, such as ethanolamine (NH2CH2CH2OH; Rivilla et al., 2021a), and propanol (CH3CH2CH2OH; Jimenez-Serra et al. 2022; Belloche et al. 2022).

In star- and planet-forming regions, this chemical feedstock can be processed through circumstellar disks, and subsequently incorporated into planetesimals and objects like comets and asteroids. We know that our planet suffered a heavy bombardment of extraterrestrial bodies ∼500 Myr after its formation (e.g. Marchi et al., 2014). Laboratory impact experiments have shown that a significant fraction of the molecules contained in comets and meteorites could have been delivered intact to the early Earth (Pierazzo and Chyba 1999; Bertrand et al., 2009; McCaffrey et al., 2014; Todd and Öberg 2020; Zellner et al., 2020). Once on the planetary surface, under the appropriate physical/chemical conditions, these molecules could have allowed the development of the prebiotic processes that led to the dawn of life on Earth.

 Data Availability Statement

The raw data supporting the conclusion of this article will be made available by the authors, without undue reservation.

 Author Contributions

VR initiated and led the project. VR, JM-P, FR-V, BT, and PdV performed the observations. VR, IJ-S, and JM-P performed the data reduction. VR, LC, SZ, and IJ-S contributed to the data analysis. LB and MM performed the calculations of the cyanoacetaldehyde spectroscopy. VR wrote an initial draft of the article. All the authors, including JG, SM and MR-T, participated in data interpretation and discussion.

 Funding

VR has received support from the Comunidad de Madrid through the Atracción de Talento Investigador Modalidad 1 (Doctores con experiencia) Grant (COOL:Cosmic Origins of Life; 2019-T1/TIC-5379), and the Ayuda RYC2020-029387-I funded by MCIN/AEI /10.13039/501100011033. IJS, JMP, and LC have received partial support from the Spanish project numbers PID2019-105552RB-C41 and MDM-2017-0737 (Unidad de Excelencia María de Maeztu-Centro de Astrobiología, INTA-CSIC). JG acknowledges the Spanish State Research Agency (AEI) through project number MDM-2017-0737 Unidad de Excelencia “María de Maeztu”—Centro de Astrobiología and the Spanish State Research Agency (AEI) for partial financial support through Project No. PID 2019-105552RB-C41. PdV and BT thank the support from the European Research Council (ERC Grant 610256: NANOCOSMOS) and from the Spanish Ministerio de Ciencia e Innovación (MICIU) through project PID 2019-107115GBC21. BT also acknowledges the Spanish MICIU for funding support from grant PID 2019-106235GB-I00.

 Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

 Publisher’s Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

We thank the two reviewers for providing very constructive and useful comments and suggestions, which contributed to improve our work. We also thank Dr. Rougal Ritson for interesting discussions about the relevance of nitriles in prebiotic chemistry. We are very grateful to the IRAM 30 m and Yebes 40 m telecope staff for their precious help during the different observing runs. IRAM is supported by the National Institute for Universe Sciences and Astronomy/National Center for Scientific Research (France), Max Planck Society for the Advancement of Science (Germany), and the National Geographic Institute (IGN) (Spain). The 40 m radio telescope at Yebes Observatory is operated by the IGN, Ministerio de Transportes, Movilidad y Agenda Urbana.

Madrid Data Cube Analysis on ImageJ is a software developed at the Center of Astrobiology (CAB) in Madrid; https://cab.inta-csic.es/madcuba/.

The position of this source is offset in (α, δ) by (20 ″ , 100 ″ ) with respect to that of Sgr B2(M), see Brünken et al. (2010).

 References Abeysekera C. Joalland B. Ariyasingha N. Zack L. N. Sims I. R. Field R. W. (2015). Product Branching in the Low Temperature Reaction of Cn with Propyne by Chirped-Pulse Microwave Spectroscopy in a Uniform Supersonic Flow. J. Phys. Chem. Lett. 6, 1599–1604. 10.1021/acs.jpclett.5b00519 Alessandrini S. Melosso M. (2021). Fate of the Gas-phase Reaction between Oxirane and the Cn Radical in Interstellar Conditions. Front. Astron. Space Sci. 8. 10.3389/fspas.2021.754977 Balucani N. Asvany O. Huang L. C. L. Lee Y. T. Kaiser R. I. Osamura Y. (2000). Formation of Nitriles in the Interstellar Medium via Reactions of Cyano Radicals, CN(X 2Σ+), with Unsaturated Hydrocarbons. Astrophysical J. 545, 892–906. 10.1086/317848 Balucani N. Asvany O. Kaiser R.-I. Osamura Y. (2002). Formation of Three C4H3N Isomers from the Reaction of CN (X2Σ+) with Allene, H2CCCH2 (XA1), and Methylacetylene, CH3CCH (X1A1): A Combined Crossed Beam and Ab Initio Study. J. Phys. Chem. A 106, 4301–4311. 10.1021/jp0116104 Becker S. Feldmann J. Wiedemann S. Okamura H. Schneider C. Iwan K. (2019). Unified Prebiotically Plausible Synthesis of Pyrimidine and Purine Rna Ribonucleotides. Science 366, 76–82. 10.1126/science.aax2747 Belloche A. Garrod R. T. Müller H. S. P. Menten K. M. Medvedev I. Thomas J. (2019). Re-exploring Molecular Complexity with ALMA (ReMoCA): Interstellar Detection of Urea. Astronomy Astrophysics 628, A10. 10.1051/0004-6361/201935428 Belloche A. Garrod R. T. Zingsheim O. Müller H. S. P. Menten K. M. (2022). Interstellar Detection and Chemical Modeling of Iso-Propanol and its Normal Isomer. arXiv e-prints. arXiv:2204.09912. 10.1051/0004-6361/202243575 Belloche A. Menten K. M. Comito C. Müller H. S. P. Schilke P. Ott J. (2008). Detection of Amino Acetonitrile in Sgr B2(N). Astronomy Astrophysics 482, 179–196. 10.1051/0004-6361:20079203 Beltrán M. T. Codella C. Viti S. Neri R. Cesaroni R. (2009). First Detection of Glycolaldehyde outside the Galactic Center. Astrophysical J. 690, L93–L96. 10.1088/0004-637X/690/2/L93 Bertrand M. van der Gaast S. Vilas F. Hörz F. Haynes G. Chabin A. (2009). The Fate of Amino Acids during Simulated Meteoritic Impact. Astrobiology 9, 943–951. 10.1089/ast.2008.0327 Bester M. Tanimoto M. Vowinkel B. Winnewisser G. Yamada K. (1983). Rotational Spectrum of Methylcyanoacetylene a New Millimeter Wave Spectrometer. Z. für Naturforsch. A 38, 64–67. 10.1515/zna-1983-0112 Bester M. Yamada K. Winnewisser G. Joentgen W. Altenbach H.-J. Vogel E. (1984). Millimeter Wave Spectrum of Methyldiacetylene, Ch3c4h. Astronomy Astrophysics 137, L20–L22. Bizzocchi L. Prudenzano D. Rivilla V. M. Pietropolli-Charmet A. Giuliano B. M. Caselli P. (2020). Propargylimine in the Laboratory and in Space: Millimetre-Wave Spectroscopy and its First Detection in the ISM. Astronomy Astrophysics 640, A98. 10.1051/0004-6361/202038083 Bogey M. Demuynck C. Destombes J. L. Vallee Y. (1995). Millimeter-wave Spectrum of Formyl Cyanide, Hcocn: Centrifugal Distortion and Hyperfine Structure Analysis. J. Mol. Spectrosc. 172, 344–351. 10.1006/jmsp.1995.1183 Bouchy A. Demaison J. Roussy G. Barriol J. (1973). Microwave Spectrum of Cyanoallene. J. Mol. Struct. 18, 211–217. 10.1016/0022-2860(73)85223-8 Brünken S. Belloche A. Martín S. Verheyen L. Menten K. M. (2010). Interstellar HOCN in the Galactic Center Region. Astronomy Astrophysics 516, A109. 10.1051/0004-6361/200912456 Brünken S. Gottlieb C. A. McCarthy M. C. Thaddeus P. (2009). Laboratory Detection of Hocn and Tentative Identification in Sgr B2. Astrophysical J. 697, 880–885. 10.1088/0004-637x/697/1/880 Canavelli P. Islam S. Powner M. W. (2019). Peptide Ligation by Chemoselective Aminonitrile Coupling in Water. Nature 571, 546–549. 10.1038/s41586-019-1371-4 Caselli P. Hartquist T. W. Havnes O. (1997). Grain-grain Collisions and Sputtering in Oblique C-type Shocks. Astronomy Astrophysics 322, 296–301. Cernicharo J. Cabezas C. Agúndez M. Tercero B. Pardo J. R. Marcelino N. (2021). TMC-1, the Starless Core Sulfur Factory: Discovery of NCS, HCCS, H2CCS, H2CCCS, and C4S and Detection of C5S. Astronomy Astrophysics 648, L3. 10.1051/0004-6361/202140642 Chyba C. Sagan C. (1992). Endogenous Production, Exogenous Delivery and Impact-Shock Synthesis of Organic Molecules: An Inventory for the Origins of Life. Nature 355, 125–132. 10.1038/355125a0 Colzi L. Martín-Pintado J. Rivilla V. M. Jiménez-Serra I. Zeng S. Rodríguez-Almeida L. F. (2022). Deuterium Fractionation as a Multiphase Component Tracer in the Galactic Center. Astrophysical JournalL 926, L22. 10.3847/2041-8213/ac52ac Cooper G. Kimmich N. Belisle W. Sarinana J. Brabham K. Garrel L. (2001). Carbonaceous Meteorites as a Source of Sugar-Related Organic Compounds for the Early Earth. Nature 414, 879–883. 10.1038/414879a Császár A. G. (1989). Theoretical Prediction of Vibrational and Rotational Spectra. Formyl Cyanide, Hcocn, and Thioformyl Cyanide, Hcscn. Chem. Phys. Lett. 162, 361–368. 10.1016/0009-2614(89)87059-9 Danger G. Duvernay F. Theulé P. Borget F. Chiavassa T. (2012). Hydroxyacetonitrile (HOCH2CN) Formation in Astrophysical Conditions. Competition with the Aminomethanol, a Glycine Precursor. Astrophysical J. 756, 11. 10.1088/0004-637X/756/1/11 Danger G. Duvernay F. Theulé P. Borget F. Guillemin J.-C. Chiavassa T. (2013). Hydroxyacetonitrile (HOCH2cn) as a Precursor for Formylcyanide (CHOCN), Ketenimine (CH2cnh), and Cyanogen (NCCN) in Astrophysical Conditions. Astronomy Astrophysics 549, A93. 10.1051/0004-6361/201219779 Demaison J. Pohl I. Rudolph H. D. (1985). Millimeter-wave Spectrum of 3-butynenitrile: Dipole Moment and Centrifugal Distortion Constants. J. Mol. Spectrosc. 114, 210–218. 10.1016/0022-2852(85)90349-2 Endres C. P. Schlemmer S. Schilke P. Stutzki J. Müller H. S. P. (2016). The Cologne Database for Molecular Spectroscopy, CDMS, in the Virtual Atomic and Molecular Data Centre, VAMDC. J. Mol. Spectrosc. 327, 95–104. 10.1016/j.jms.2016.03.005 Erian A. W. (1993). The Chemistry of .beta.-enaminonitriles as Versatile Reagents in Heterocyclic Synthesis. Chem. Rev. 93, 1991–2005. 10.1021/cr00022a002 Foden C. S. Islam S. Fernández-García C. Maugeri L. Sheppard T. D. Powner M. W. (2020). Prebiotic Synthesis of Cysteine Peptides that Catalyze Peptide Ligation in Neutral Water. Science 370, 865–869. 10.1126/science.abd5680 Garrod R. T. Weaver S. L. W. Herbst E. (2008). Complex Chemistry in Star‐forming Regions: An Expanded Gas‐Grain Warm‐up Chemical Model. Astrophysical J. 682, 283–302. 10.1086/588035 Gilbert W. (1986). Origin of Life: The RNA World. Nature 319, 618. 10.1038/319618a0 Harris A. I. Güsten R. Requena-Torres M. A. Riquelme D. Morris M. R. Stacey G. J. (2021). SOFIA-upGREAT Imaging Spectroscopy of the [C Ii] 158 μm Fine-structure Line of the Sgr B Region in the Galactic Center. Astrophysical J. 921, 33. 10.3847/1538-4357/ac1863 Hasegawa T. I. Herbst E. (1993). New Gas-Grain Chemical Models of Quiescent Dense Interstellar Clouds: the Effects of H2 Tunnelling Reactions and Cosmic Ray Induced Desorption. Mon. Notices R. Astronomical Soc. 261, 83–102. 10.1093/mnras/261.1.83 Hollis J. M. Jewell P. R. Lovas F. J. Remijan A. (2004). Green Bank Telescope Observations of Interstellar Glycolaldehyde: Low-Temperature Sugar. Astrophysical J. 613, L45–L48. 10.1086/424927 Horn A. Møllendal H. Guillemin J.-C. (2008). A Quantum Chemical Study of the Generation of a Potential Prebiotic Compound, Cyanoacetaldehyde, and Related Sulfur Containing Species. J. Phys. Chem. A 112, 11009–11016. 10.1021/jp805357w Jiménez-Serra I. Caselli P. Martín-Pintado J. Hartquist T. W. (2008). Parametrization of C-Shocks. Evolution of the Sputtering of Grains. Astronomy Astrophysics 482, 549–559. 10.1051/0004-6361:20078054 Jiménez-Serra I. Martín-Pintado J. Rivilla V. M. Rodríguez-Almeida L. Alonso Alonso E. R. Zeng S. (2020). Toward the RNA-World in the Interstellar Medium-Detection of Urea and Search of 2-Amino-Oxazole and Simple Sugars. Astrobiology 20, 1048–1066. 10.1089/ast.2019.2125 Jimenez-Serra I. Rodriguez-Almeida L. F. Martin-Pintado J. Rivilla V. M. Melosso M. Zeng S. (2022). Precursors of Fatty Alcohols in the ISM: Discovery of N-Propanol. arXiv e-prints. arXiv:2204.08267. 10.1051/0004-6361/202142699 Jørgensen J. K. Favre C. Bisschop S. E. Bourke T. L. van Dishoeck E. F. Schmalzl M. (2012). Detection of the Simplest Sugar, Glycolaldehyde, in a Solar-type Protostar with ALMA. Astrophysical J. 757, L4. 10.1088/2041-8205/757/1/L4 Ligterink N. F. W. Ahmadi A. Coutens A. Tychoniec Ł. Calcutt H. van Dishoeck E. F. (2021). The Prebiotic Molecular Inventory of Serpens SMM1. Astronomy Astrophysics 647, A87. 10.1051/0004-6361/202039619 Liu Z. Mariani A. Wu L. Ritson D. Folli A. Murphy D. (2018). Tuning the Reactivity of Nitriles Using Cu(ii) Catalysis - Potentially Prebiotic Activation of Nucleotides. Chem. Sci. 9, 7053–7057. 10.1039/c8sc02513d Lovas F. J. Remijan A. J. Hollis J. M. Jewell P. R. Snyder L. E. (2006). Hyperfine Structure Identification of Interstellar Cyanoallene toward Tmc-1. Astrophysical J. 637, L37–L40. 10.1086/500431 Marcelino N. Agúndez M. Cernicharo J. Roueff E. Tafalla M. (2018). Discovery of the Elusive Radical NCO and Confirmation of H2NCO+ in Space. Astronomy Astrophysics 612, L10. 10.1051/0004-6361/201833074 Marcelino N. Brünken S. Cernicharo J. Quan D. Roueff E. Herbst E. (2010). The Puzzling Behavior of HNCO Isomers in Molecular Clouds. Astronomy Astrophysics 516, A105. 10.1051/0004-6361/200913806 Marcelino N. Tercero B. Agúndez M. Cernicharo J. (2021). A Study of C4H3N Isomers in TMC-1: Line by Line Detection of HCCCH2CN. Astronomy Astrophysics 646, L9. 10.1051/0004-6361/202040177 Marchi S. Bottke W. F. Elkins-Tanton L. T. Bierhaus M. Wuennemann K. Morbidelli A. (2014). Widespread Mixing and Burial of Earth's Hadean Crust by Asteroid Impacts. Nature 511, 578–582. 10.1038/nature13539 Margulès L. McGuire B. A. Senent M. L. Motiyenko R. A. Remijan A. Guillemin J. C. (2017). Submillimeter Spectra of 2-hydroxyacetonitrile (Glycolonitrile; HOCH2cn) and its Searches in GBT PRIMOS Observations of Sgr B2(N). Astronomy Astrophysics 601, A50. 10.1051/0004-6361/201628551 Mariani A. Russell D. A. Javelle T. Sutherland J. D. (2018). A Light-Releasable Potentially Prebiotic Nucleotide Activating Agent. J. Am. Chem. Soc. 140, 8657–8661. 10.1021/jacs.8b05189 Martín S. Martín-Pintado J. Blanco-Sánchez C. Rivilla V. M. Rodríguez-Franco A. Rico-Villas F. (2019). Spectral Line Identification and Modelling (SLIM) in the MAdrid Data CUBe Analysis (MADCUBA) Package. Astronomy Astrophysics 631, A159. 10.1051/0004-6361/201936144 Martín S. Requena‐Torres M. A. Martín‐Pintado J. Mauersberger R. (2008). Tracing Shocks and Photodissociation in the Galactic Center Region1. Astrophysical J. 678, 245–254. 10.1086/533409 Martín-Pintado J. Rizzo J. R. de Vicente P. Rodríguez-Fernández N. J. Fuente A. (2001). Large-Scale Grain Mantle Disruption in the Galactic Center. Astrophysical JournalL 548, L65–L68. 10.1086/318937 McCaffrey V. P. Zellner N. E. B. Waun C. M. Bennett E. R. Earl E. K. (2014). Reactivity and Survivability of Glycolaldehyde in Simulated Meteorite Impact Experiments. Orig. Life Evol. Biosph. 44, 29–42. 10.1007/s11084-014-9358-5 McGuire B. A. Burkhardt A. M. Loomis R. A. Shingledecker C. N. Kelvin Lee K. L. Charnley S. B. (2020). Early Science from Gotham: Project Overview, Methods, and the Detection of Interstellar Propargyl Cyanide (Hccch2cn) in Tmc-1. Astrophysical J. 900, L10. 10.3847/2041-8213/aba632 Melosso M. Belloche A. Martin-Drumel M.-A. Pirali O. Tamassia F. Bizzocchi L. (2020). Far-infrared Laboratory Spectroscopy of Aminoacetonitrile and First Interstellar Detection of its Vibrationally Excited Transitions. Astronomy Astrophysics 641, A160. 10.1051/0004-6361/202038466 Menor Salván C. Bouza M. Fialho D. M. Burcar B. T. Fernández F. M. Hud N. V. (2020). Prebiotic Origin of Pre‐RNA Building Blocks in a Urea "Warm Little Pond" Scenario. ChemBioChem 21, 3504–3510. 10.1002/cbic.202000510 Menor-Salván C. Marín-Yaseli M. R. (2012). Prebiotic Chemistry in Eutectic Solutions at the Water-Ice Matrix. Chem. Soc. Rev. 41, 5404–5415. 10.1039/c2cs35060b Menor-Salván C. Ruiz-Bermejo D. M. Guzmán M. I. Osuna-Esteban S. Veintemillas-Verdaguer S. (2009). Synthesis of Pyrimidines and Triazines in Ice: Implications for the Prebiotic Chemistry of Nucleobases. Chem. Eur. J. 15, 4411–4418. 10.1002/chem.200802656 Moïses A. Boucher D. Burie J. Demaison J. Dubrulle A. (1982). Millimeter-wave Spectrum of Methylcyanoacetylene. J. Mol. Spectrosc. 92, 497–498. 10.1016/0022-2852(82)90118-7 Møllendal H. Margulès L. Motiyenko R. A. Larsen N. W. Guillemin J.-C. (2012). Rotational Spectrum and Conformational Composition of Cyanoacetaldehyde, a Compound of Potential Prebiotic and Astrochemical Interest. J. Phys. Chem. A 116, 4047–4056. 10.1021/jp212306z Nelson K. E. Robertson M. P. Levy M. Miller S. L. (2001). Concentration by Evaporation and the Prebiotic Synthesis of Cytosine. Orig. Life Evol. Biosphere 31, 221–229. 10.1023/a:1010652418557 Oró J. (1961). Mechanism of Synthesis of Adenine from Hydrogen Cyanide under Possible Primitive Earth Conditions. Nature 191, 1193–1194. 10.1038/1911193a0 Patel B. H. Percivalle C. Ritson D. J. Duffy C. D. Sutherland J. D. (2015). Common Origins of RNA, Protein and Lipid Precursors in a Cyanosulfidic Protometabolism. Nat. Chem. 7, 301–307. 10.1038/nchem.2202 Pearce B. K. D. Tupper A. S. Pudritz R. E. Higgs P. G. (2018). Constraining the Time Interval for the Origin of Life on Earth. Astrobiology 18, 343–364. 10.1089/ast.2017.1674 Pickett H. M. Poynter R. L. Cohen E. A. Delitsky M. L. Pearson J. C. Müller H. S. P. (1998). Submillimeter, Millimeter, and Microwave Spectral Line Catalog. J. Quantitative Spectrosc. Radiat. Transf. 60, 883–890. 10.1016/S0022-4073(98)00091-0 Pickett H. M. (1991). The Fitting and Prediction of Vibration-Rotation Spectra with Spin Interactions. J. Mol. Spectrosc. 148, 371–377. 10.1016/0022-2852(91)90393-O Pierazzo E. Chyba C. F. (1999). Amino Acid Survival in Large Cometary Impacts. Meteorit. Planet. Sci. 34, 909–918. 10.1111/j.1945-5100.1999.tb01409.x Powner M. W. Gerland B. Sutherland J. D. (2009). Synthesis of Activated Pyrimidine Ribonucleotides in Prebiotically Plausible Conditions. Nature 459, 239–242. 10.1038/nature08013 Powner M. W. Sutherland J. D. (2010). Phosphate-mediated Interconversion of Ribo- and Arabino-Configured Prebiotic Nucleotide Intermediates. Angew. Chem. Int. Ed. 49, 4641–4643. 10.1002/anie.201001662 Quénard D. Jiménez-Serra I. Viti S. Holdship J. Coutens A. (2018). Chemical Modelling of Complex Organic Molecules with Peptide-like Bonds in Star-Forming Regions. Mon. Notices R. Astronomical Soc. 474, 2796–2812. 10.1093/mnras/stx2960 Remijan A. J. Hollis J. M. Lovas F. J. Stork W. D. Jewell P. R. Meier D. S. (2008). Detection of Interstellar Cyanoformaldehyde (CNCHO). Astrophysical J. 675, L85–L88. 10.1086/533529 Requena-Torres M. A. Martín-Pintado J. Martín S. Morris M. R. (2008). The Largest Oxigen Bearing Organic Molecule Repository. Astrophysical J. 672, 352–360. 10.1086/523627 Requena-Torres M. A. Martín-Pintado J. Rodríguez-Franco A. Martín S. Rodríguez-Fernández N. J. de Vicente P. (2006). Organic Molecules in the Galactic Center. Astronomy Astrophysics 455, 971–985. 10.1051/0004-6361:20065190 Ritson D. J. Battilocchio C. Ley S. V. Sutherland J. D. (2018). Mimicking the Surface and Prebiotic Chemistry of Early Earth Using Flow Chemistry. Nat. Commun. 9, 1821. 10.1038/s41467-018-04147-2 Ritson D. J. Sutherland J. D. (2013). Synthesis of Aldehydic Ribonucleotide and Amino Acid Precursors by Photoredox Chemistry. Angew. Chem. Int. Ed. 52, 5845–5847. 10.1002/anie.201300321 Ritson D. Sutherland J. D. (2012). Prebiotic Synthesis of Simple Sugars by Photoredox Systems Chemistry. Nat. Chem. 4, 895–899. 10.1038/nchem.1467 Rivilla V. M. Beltrán M. T. Vasyunin A. Caselli P. Viti S. Fontani F. (2019a). First ALMA Maps of HCO, an Important Precursor of Complex Organic Molecules, towards IRAS 16293-2422. MNRAS 483, 806–823. 10.1093/mnras/sty3078 Rivilla V. M. Colzi L. Jiménez-Serra I. Martín-Pintado J. Megías A. Melosso M. (2022a). Precursors of the RNA World in Space: Detection of (Z)-1,2-ethenediol in the Interstellar Medium, a Key Intermediate in Sugar Formation. Astrophysical JournalL 929, L11. 10.3847/2041-8213/ac6186 Rivilla V. M. García De La Concepción J. Jiménez-Serra I. Martín-Pintado J. Colzi L. Tercero B. (2022b). Ionize Hard: Interstellar PO+ Detection. Front. Astron. Space Sci. 9, 829288. 10.3389/fspas.2022.829288 Rivilla V. M. Jiménez-Serra I. García de la Concepción J. Martín-Pintado J. Colzi L. Rodríguez-Almeida L. F. (2021b). Detection of the Cyanomidyl Radical (HNCN): a New Interstellar Species with the NCN Backbone. MNRAS 506, L79–L84. 10.1093/mnrasl/slab074 Rivilla V. M. Jiménez-Serra I. Martín-Pintado J. Briones C. Rodríguez-Almeida L. F. Rico-Villas F. (2021a). Discovery in Space of Ethanolamine, the Simplest Phospholipid Head Group. Proc. Natl. Acad. Sci. U.S.A. 118, e2101314118. 10.1073/pnas.2101314118 Rivilla V. M. Martín-Pintado J. Jiménez-Serra I. Martín S. Rodríguez-Almeida L. F. Requena-Torres M. A. (2020). Prebiotic Precursors of the Primordial RNA World in Space: Detection of NH2OH. Astrophysical J. 899, L28. 10.3847/2041-8213/abac55 Rivilla V. M. Martín-Pintado J. Jiménez-Serra I. Zeng S. Martín S. Armijos-Abendaño J. (2019b). Abundant Z-Cyanomethanimine in the Interstellar Medium: Paving the Way to the Synthesis of Adenine. MNRAS 483, L114–L119. 10.1093/mnrasl/sly228 Robertson M. P. Miller S. L. (1995). An Efficient Prebiotic Synthesis of Cytosine and Uracil. Nature 375, 772–774. 10.1038/375772a0 Rodriguez L. E. House C. H. Smith K. E. Roberts M. R. Callahan M. P. (2019). Nitrogen Heterocycles Form Peptide Nucleic Acid Precursors in Complex Prebiotic Mixtures. Sci. Rep. 9, 9281. 10.1038/s41598-019-45310-z Rodríguez-Almeida L. F. Jiménez-Serra I. Rivilla V. M. Martín-Pintado J. Zeng S. Tercero B. (2021a). Thiols in the Interstellar Medium: First Detection of HC(O)SH and Confirmation of C2H5SH. Astrophysical JournalL 912, L11. 10.3847/2041-8213/abf7cb Rodríguez-Almeida L. F. Rivilla V. M. Jiménez-Serra I. Melosso M. Colzi L. Zeng S. (2021b). First Detection of C2H5NCO in the ISM and Search of Other Isocyanates towards the G+0.693-0.027 Molecular Cloud. Astronomy Astrophysics 654, L1. 10.1051/0004-6361/202141989 Rodríguez-Fernández N. J. Tafalla M. Gueth F. Bachiller R. (2010). HNCO Enhancement by Shocks in the L1157 Molecular Outflow. Astronomy Astrophysics 516, A98. 10.1051/0004-6361/201013997 Rosi M. Skouteris D. Casavecchia P. Falcinelli S. Ceccarelli C. Balucani N. (2018). “Formation of Nitrogen-Bearing Organic Molecules in the Reaction NH + C2H5: A Theoretical Investigation and Main Implications for Prebiotic Chemistry in Space,” in International conference on computational science and its applications (Berlin, Germany: Springer), 773–782. 10.1007/978-3-319-95165-2_54 Schwahn G. Schieder R. Bester M. Winnewisser G. (1986). The Millimeter Wave Spectrum of Cyanoallene, CH2 ⋅ C ⋅ CH ⋅ CN, Using a New Digital Lock-In Technique. J. Mol. Spectrosc. 116, 263–270. 10.1016/0022-2852(86)90126-8 Schwartz A. W. Goverde M. (1982). Acceleration of Hcn Oligomerization by Formaldehyde and Related Compounds: Implications for Prebiotic Syntheses. J. Mol. Evol. 18, 351–353. 10.1007/bf01733902 Shriner R. L. Neumann F. W. (1944). The Chemistry of the Amidines. Chem. Rev. 35, 351–425. 10.1021/cr60112a002 Tercero F. López-Pérez J. A. Gallego J. D. Beltrán F. García O. Patino-Esteban M. (2021). Yebes 40 M Radio Telescope and the Broad Band Nanocosmos Receivers at 7 Mm and 3 Mm for Line Surveys. Astronomy Astrophysics 645, A37. 10.1051/0004-6361/202038701 Todd Z. R. Öberg K. I. (2020). Cometary Delivery of Hydrogen Cyanide to the Early Earth. Astrobiology 20, 1109–1120. 10.1089/ast.2019.2187 Tonolo F. Lupi J. Puzzarini C. Barone V. (2020). The Quest for a Plausible Formation Route of Formyl Cyanide in the Interstellar Medium: a State-Of-The-Art Quantum-Chemical and Kinetic Approach. Astrophysical J. 900, 85. 10.3847/1538-4357/aba628 Turner B. E. (1971). Detection of Interstellar Cyanoacetylene. Astrophysical J. 163, L35. 10.1086/180662 Turner B. E. Liszt H. S. Kaifu N. Kisliakov A. G. (1975). Microwave Detection of Interstellar Cyanamide. Astrophysical J. 201, L149–L152. 10.1086/181963 Woon D. E. (2021). The Formation of Glycolonitrile (HOCH2CN) from Reactions of C+ with HCN and HNC on Icy Grain Mantles. Astrophysical J. 906, 20. 10.3847/1538-4357/abc691 Zellner N. E. B. McCaffrey V. P. Butler J. H. E. (2020). Cometary Glycolaldehyde as a Source of Pre-rna Molecules. Astrobiology 20, 1377–1388. 10.1089/ast.2020.2216 Zeng S. Jiménez-Serra I. Rivilla V. M. Martín S. Martín-Pintado J. Requena-Torres M. A. (2018). Complex Organic Molecules in the Galactic Centre: the N-Bearing Family. Mon. Notices R. Astronomical Soc. 478, 2962–2975. 10.1093/mnras/sty1174 Zeng S. Jiménez-Serra I. Rivilla V. M. Martín-Pintado J. Rodríguez-Almeida L. F. Tercero B. (2021). Probing the Chemical Complexity of Amines in the ISM: Detection of Vinylamine (C2H3NH2) and Tentative Detection of Ethylamine (C2H5NH2). Astrophysical JournalL 920, L27. 10.3847/2041-8213/ac2c7e Zeng S. Quénard D. Jiménez-Serra I. Martín-Pintado J. Rivilla V. M. Testi L. (2019). First Detection of the Pre-biotic Molecule Glycolonitrile (HOCH2CN) in the Interstellar Medium. MNRAS 484, L43–L48. 10.1093/mnrasl/slz002 Zeng S. Zhang Q. Jiménez-Serra I. Tercero B. Lu X. Martín-Pintado J. (2020). Cloud-cloud Collision as Drivers of the Chemical Complexity in Galactic Centre Molecular Clouds. MNRAS 497, 4896–4909. 10.1093/mnras/staa2187