Experimental investigation of aminoacetonitrile formation through the Strecker synthesis in astrophysical-like conditions: reactivity of methanimine (CH₂NH), ammonia (NH₃), and hydrogen cyanide (HCN)

Abstract

Context. Studing chemical reactivity in astrophysical environments is an important means for improving our understanding of the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system. Laboratory simulations of the reactivity of ice analogs provide important insight into the reactivity in these environments. Here, we use these experimental simulations to investigate the Strecker synthesis leading to the formation of aminoacetonitrile in astrophysicallike conditions. The aminoacetonitrile is an interesting compound because it was detected in SgrB2, hence could be a precursor of the smallest amino acid molecule, glycine, in astrophysical environments. Aims. We present the first experimental investigation of the formation of aminoacetonitrile NH 2 CH 2 CN from the thermal processing of ices including methanimine (CH 2 NH), ammonia (NH 3 ), and hydrogen cyanide (HCN) in interstellar-like conditions without VUV photons or particules. Methods. We use Fourier Transform InfraRed (FTIR) spectroscopy to monitor the ice evolution during its warming. Infrared spectroscopy and mass spectroscopy are then used to identify the aminoacetonitrile formation. Results. We demonstrate that methanimine can react with − CN during the warming of ice analogs containing at 20 K methanimine, ammonia, and [NH + 4− CN] salt. During the ice warming, this reaction leads to the formation of poly(methylene-imine) polymers. The polymer length depend on the initial ratio of mass contained in methanimine to that in the [NH + 4− CN] salt. In a methanimine excess, long polymers are formed. As the methanimine is progressively diluted in the [NH + 4− CN] salt, the polymer length decreases until the aminoacetonitrile formation at 135 K. Therefore, these results demonstrate that aminoacetonitrile can be formed through the second step of the Strecker synthesis in astrophysical-like conditions.

SURVEY OBSERVATIONS OF A POSSIBLE GLYCINE PRECURSOR, METHANIMINE (CH2NH)

“…If this is the case, CH 2 NH might not be a direct precursor to CH 3 NH 2 . CH 2 NH is related to another formation path for glycine; if a H atom and HCN are added to CH 2 NH on the grain surface, aminoacetonitrile (NH 2 CH 2 CN) could be formed (Danger et al 2011). NH 2 CH 2 CN yields glycine via hydrolysis (Peltzer et al 1984).…”

Importance of thermal reactivity for hexamethylenetetramine formation from simulated interstellar ices

“…4). PMI is a polymer identified by Danger et al (2011) and Vinogradoff et al (2012b) in ice mixtures containing methylenimine, CH 2 NH. Interestingly, the pure imine (CH 2 NH) does not A128, page 4 of 9 V. Vinogradoff et al: Chemistry of interstellar residue analogues lead to HMT in the interstellar-like conditions (Vinogradoff et al 2012b) and has to be catalysed by the formic acid.…”

“…A small fraction of new refractory species is of high molecular mass, up to 4000 amu at room temperature (Danger et al 2012b), this material is generally called refractory organic residue, or simply residue. Large organic compounds are produced either by ice photoprocessing (Agarwal et al 1985;Briggs et al 1992;Bernstein et al 1995;Muñoz Caro & Schutte 2003;Muñoz Caro et al 2004), by ion bombardment (Cottin et al 2001;Strazzulla & Baratta 1992;Kobayashi et al 1995;Kaiser & Roessler 1998), or by thermal processes (Bossa et al 2009;Vinogradoff et al 2011;Danger et al 2011;Vinogradoff et al 2013Vinogradoff et al , 2012a.…”

Formaldehyde and methylamine reactivity in interstellar ice analogues as a source of molecular complexity at low temperature

“…The non-detection so far of these compounds in the gas phase comes from the lack of rotational spectra for these molecules. From an astrobiological point of view, aminoalcohols are interesting molecules because they are considered as amino acid precursors in the Strecker synthesis (Bossa et al 2009b;Duvernay et al 2010;Vinogradoff et al 2011;Rimola et al 2010;Danger et al 2011). In our case the N-methylaminomethanol will form through the Strecker synthesis the corresponding amino acid, the sarcosine (Eq.…”