Fundamental Vibrational Frequencies and Spectroscopic Constants for Additional Tautomers and Conformers of NH2CHCO

The creation of larger prebiotic molecules in astronomical regions may require aminoketene (NH2CHCO) as an intermediate, and the two conformers of this molecule exhibit infrared vibrational frequencies with intensities larger even than the antisymmetric stretch in CO2. While the present quantum chemically computed frequencies of these fundamentals of ∼4.7 μm are in the same spectroscopic region as features from functionalized polycyclic aromatic hydrocarbons, they provide clear markers for what James Webb Space Telescope IR observations may be able to distinguish. Additionally, the IR and radioastronomical spectral characterization of two additional 2-iminoacetaldehyde, HN=CHC(=O)H, conformers are also computed as are the same data for a new carbene isomer (NH2CC(=O)H). All conformers of aminoketene and 2-iminoacetaldehyde exhibit dipole moments of more than 2.0 D, if not greater than 4.0 D, implying that they would be notable targets for radioastronomical searches. Additionally, the 2-iminoacetaldehyde conformers have a notable mid-IR C=O stretch around 1735 cm−1 slightly below the same fundamental in formaldehyde. This quantum chemical study is providing a more complete set of reference data for the potential observation of these tautomers and conformers of NH2CHCO in the laboratory or even in space.