Acetamide, CH3C(O)NH2, has been identified with the 100 m GBT in spectra recorded toward Sgr B2(N) by
J. M. Hollis, F. J. Lovas, A. R. Remijan, P. R. Jewell, V. V. Ilyushin, and I. Kleiner,
Detection of Acetamide (CH<sub>3</sub>CONH<sub>2</sub>): the Largest Interstellar Molecule with a Peptide Bond
Astrophys. J. 643, L25–L28 (2006).
Eight different tunneling components (4 A and 4 E) of eight different low-J transitions have been detected mostly in absorption and mostly between 9 and 23 GHz. Some formamide transitions were also studied.

Additional extensive observations of formamide and acetamide have been detected between 65 and 280 GHz employing the ARO 12  and SMT instruments by
D. T. Halfen, V. V. Ilyushin, and L. M. Ziurys,
Formation of Peptide Bonds in Space: A Comprehensive Study of Formamide and Acetamide in Sgr B2(N)
Astrophys. J. 743, Art. No. 60 (2011).
While the observational results are important, the quantitative interpretations, in particular the column densities as well as the column density ratio, should be viewed with great caution. First, the assumption, that all formamide lines are optically thin, is unlikely fulfilled, and it is conceivable that some of the acetamide lines are not optically thin, either. Second, the assumption, that the hot cores of Sgr B2(N) fill the telescope beam, is definitively not valid.
The authors did not find any evidence for the acetamide isomer N-methyl formamide in their spectra and pointed out: “These data are further evidence that interstellar chemistry is not combinatorial.” Or in other words: astrochemistry is not only about astronomy, but also about chemistry !

A. Belloche, H. S. P. Müller, K. M. Menten, P. Schilke, and C. Comito
Complex Organic Molecules in the Interstellar Medium: IRAM 30 m Line Survey of Sagittarius B2(N) and (M)
Astron. Astrophys. 559, Art. No. A47 (2013).
They observed several transitions in the two lowest excited torsional state.

N. F. W. Ligterink, S. J. El-Abd, C. L. Brogan, T. R. Hunter, A. J. Remijan, R. T. Garrod, and B. M. McGuire
The Family of Amide Molecules toward NGC 6334I
Astrophys. J. 901, Art. No. 37 (2020).
They detected the molecule toward the position MM1-i among others.

Contributor(s): H. S. P. Müller; 4, 2006; 12, 2011; 04, 2019; 10, 2020

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