Rotational spectroscopic study and astronomical search for propiolamide in Sgr B2(N)

Abstract

Context. For all the amides detected in the interstellar medium (ISM), the corresponding nitriles or isonitriles have also been detected in the ISM, some of which have relatively high abundances. Among the abundant nitriles for which the corresponding amide has not yet been detected is cyanoacetylene (HCCCN), whose amide counterpart is propiolamide (HCCC(O)NH2). Aims. With the aim of supporting searches for this amide in the ISM, we provide a complete rotational study of propiolamide from 6 to 440 GHz. Methods. Time-domain Fourier transform microwave spectroscopy under supersonic expansion conditions between 6 and 18 GHz was used to accurately measure and analyze ground-state rotational transitions with resolved hyperfine structure arising from nuclear quadrupole coupling interactions of the 14N nucleus. We combined this technique with the frequency-domain room-temperature millimeter wave and submillimeter wave spectroscopies from 75 to 440 GHz in order to record and assign the rotational spectra in the ground state and in the low-lying excited vibrational states. We used the ReMoCA spectral line survey performed with the Atacama Large Millimeter/submillimeter Array toward the star-forming region Sgr B2(N) to search for propiolamide. Results. We identified and measured more than 5500 distinct frequency lines of propiolamide in the laboratory. These lines were fitted using an effective semi-rigid rotor Hamiltonian with nuclear quadrupole coupling interactions taken into consideration. We obtained accurate sets of spectroscopic parameters for the ground state and the three low-lying excited vibrational states. We report the nondetection of propiolamide toward the hot cores Sgr B2(N1S) and Sgr B2(N2). We find that propiolamide is at least 50 and 13 times less abundant than acetamide in Sgr B2(N1S) and Sgr B2(N2), respectively, indicating that the abundance difference between both amides is more pronounced by at least a factor of 8 and 2, respectively, than for their corresponding nitriles. Conclusions. Although propiolamide has yet to be included in astrochemical modeling networks, the observed upper limit to the ratio of propiolamide to acetamide seems consistent with the ratios of related species as determined from past simulations. The comprehensive spectroscopic data presented in this paper will aid future astronomical searches.

Laboratory rotational spectroscopy of acrylamide and a search for acrylamide and propionamide toward Sgr B2(N) with ALMA

“…(j) The parameters were derived from the ReMoCA survey by Belloche et al (2019). (k) The upper limit was derived from the ReMoCA survey by Alonso et al (2021).…”

“…Since COMs might be present in multiple conformations which, in addition, might be governed with large amplitude motions and low-frequency vibrations, their dense rotational spectra might be difficult to interpret. Extensive spectroscopic studies of complex amides such as N-methylformamide (Belloche et al 2017), glycolamide (Sanz-Novo et al 2020), propiolamide (Alonso et al 2021), and glycinamide (Kisiel et al 2022) were thus conducted to enable their interstellar hunt in the millimeter wave region. However, this has not been the case so far for acrylamide, whose rotational spectrum has been studied only up to 60 GHz (Marstokk et al 2000).…”

C2H5NO Isomers: From Acetamide to 1,2-Oxazetidine and Beyond

“…8 Since nitriles are abundant in the interstellar medium (ISM), Alonso et al speculated that the hydrolysis of cyanoacetylene, H–C≡C–C≡N, would lead to the formation of 2-propynamide, H–C≡C–CONH 2 ; however, the search was unsuccesful. 9 …”

Fate of the Gas-Phase Reaction Between Oxirane and the CN Radical in Interstellar Conditions

“…For example, despite the simple chemical formula and the fact that far more complex species have been identified in space (see, e.g., isopropyl cyanide (Belloche et al, 2014) or ethyl methyl ether (Tercero et al, 2015)), no members belonging to the C 3 H 3 NO family have ever been detected in the ISM. Indeed, both the search of propiolamide [HCCC(O)NH 2 ] towards Sagittarius B2 (Alonso et al, 2021) as well as the tentative observation of cyanooxirane [c-C 2 H 3 OCN] in dark clouds and hot-core sources (Dickens et al, 1996;Wirström et al, 2007) resulted unsuccessful. As it is clear that the family of C 3 H 3 NO isomers remains elusive, it is even less clear which isomer is expected to be the most abundant one and whether any of these species can be efficiently formed in the ISM or not.…”