Rotational spectrum of a chiral amino acid precursor, 2-aminopropionitrile, and searches for it in Sagittarius B2(N)

Abstract

Context. No chiral molecule has been detected in the interstellar medium (ISM) so far. Aims. A good candidate for an interstellar detection is 2-aminopropionitrile (CH 3 CH(NH 2 )CN), a chiral molecule with a C 3 H 6 N 2 formula. The first member of this series, aminoacetonitrile (H 2 NCH 2 CN), was recently detected, demonstrating that at least one aminonitrile exists in the ISM. Methods. Experimental spectra of 2-aminopropionitrile have been recorded in the microwave and submm energy range . Ab initio calculations facilitated the assignment of the ground state of the most stable conformer and its five lowest excited vibrational states. An unbiased spectral survey of the 80-116 GHz atmospheric window performed with the IRAM 30 m telescope was used to search for this molecule in the hot core Sgr B2(N). This survey was analyzed in the local thermodynamical equilibrium (LTE) approximation. The emission of 2-aminopropionitrile was modeled simultaneously with the emission of all molecules known in Sgr B2(N), which allowed us to properly take into account line blending and avoid misassignments. Results. More than 4000 lines of the ground state and the five lowest excited vibrational states (from 185 to 375 cm −1 ) were assigned in the experimental spectrum. The partition function including the vibrational contribution of these states was calculated. Only ten groups of transitions of 2-aminopropionitrile are not severely affected by line blending in the Sgr B2(N) spectrum. Six of them could be considered as tentatively detected but the LTE predictions of the four remaining groups are not (or only marginally) consistent with the observed spectrum. Therefore, only an upper limit of 1.7 × 10 16 cm −2 can be securely derived for the column density of 2-aminopropionitrile toward Sgr B2(N), assuming the same source size, temperature, linewidth, and systemic velocity as for aminoacetonitrile Conclusions. 2-aminopropionitrile is at least 1.8 times less abundant than aminoacetonitrile. A simple comparison to the pair methyl cyanide (CH 3 CN)/ethyl cyanide (CH 3 CH 2 CN) detected toward Sgr B2(N) suggests that 2-aminopropionitrile should be 3.5 times less abundant than aminoacetonitrile, which is consistent with the limit derived here.

Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)

“…Upper limits to the column densities of glycine (NH 2 CH 2 COOH), methoxyacetonitrile (CH 3 OCH 2 CN), 2-cyanoethanol (HOCH 2 CH 2 CN), 2-aminopropionitrile (CH 3 CH(NH 2 )CN), and n-butyl cyanide (n-C 4 H 9 CN) based on our spectral survey of Sgr B2(N) were reported elsewhere Braakman et al 2010;Møllendal et al 2012;Ordu et al 2012). In this section, we list a few additional upper limits derived from our survey for species that were either claimed to be detected toward Sgr B2(N) by other authors, or that are of some interest for astrochemistry.…”

“…The main goal of the survey was to search for new complex organic molecules in the gas phase of the interstellar medium. This has been partially addressed in a number of earlier publications (Belloche et al , 2009Müller et al 2008;Brünken et al 2010;Braakman et al 2010;Møllendal et al 2012;Ordu et al 2012). This article now presents the complete analysis of the full survey, the main goal being to provide a reliable identification of the detected lines.…”

The millimeter and sub-millimeter rotational spectrum of triple 13C-substituted ethyl cyanide

“…Several spectroscopic investigations were performed in support of this study, for example on iso-propyl cyanide (Müller et al 2011), anti-ethanol with one 13 C (Bouchez et al 2012), 2-aminopropionitrile (Møllendal et al 2012), and n-butyl cyanide (Ordu et al 2012). In addition, a number of spectroscopic studies have been prompted by the results of these line surveys, for example, on methyleneaminoacetonitrile (Motiyenko et al 2013), aminoacetonitrile (Motoki et al 2013), and 1,2-propanediol (Bossa et al 2014).…”

Role of Ultraviolet Radiation in the Origin of Life

“…So far, no chiral compound has been detected in the interstellar medium (Møllendal et al 2012). The excesses in Table 27.2 are far from homochirality, but mechanisms have been proposed for prebiological increase of enantiomeric excess, once some excess has been achieved (Fletcher et al 2007;Noorduin et al 2009;Hein et al 2011).…”