On the Formation of Amide Polymers via Carbonyl–amino Group Linkages in Energetically Processed Ices of Astrophysical Relevance

Abstract

We report on the formation of organic amide polymers via carbonyl-amino group linkages in carbon monoxide and ammonia bearing energetically processed ices of astrophysical relevance. The first group comprises molecules with one carboxyl group and an increasing number of amine moieties starting with formamide (45 u), urea (60 u), and hydrazine carboxamide (75 u). The second group consists of species with two carboxyl (58 u) and up to three amine groups (73 u, 88 u, and 103 u). The formation and polymerization of these linkages from simple inorganic molecules via formamide und urea toward amide polymers is discussed in an astrophysical and astrobiological context. Our results show that long chain molecules, which are closely related to polypeptides, easily form by energetically processing simple, inorganic ices at very low temperatures and can be released into the gas phase by sublimation of the ices in star-forming regions. Our experimental results were obtained by employing reflectron time-of-flight mass spectroscopy, coupled with soft, single photon vacuum ultraviolet photoionization; they are complemented by theoretical calculations.

A Vacuum Ultraviolet Photoionization Study on the Formation of N-methyl Formamide (HCONHCH3) in Deep Space: A Potential Interstellar Molecule with a Peptide Bond

“…These findings allow speculation about the formation and presence of peptide bonds toward organic molecules in astrophysically relevant ices. Förstel et al (2016b) reported the results of polyamide formation in irradiated ice mixtures of carbon monoxide (CO) with ammonia (NH 3 ). Furthermore, Halfen et al (2011) predicted an abiotic formation for polypeptide under interstellar conditions similar to the present study.…”

“…This ice growth was monitored online and in situ via an interference pattern of the HeNe laser (λ=632.8 nm; CVI Melles-Griot; 25-LHP-230) reflected from the silver wafer and the ice surface. The recorded fringes translate into an ice thickness via Equation (1), which defines the thickness (d) of an ice and the dependence on the number of interference fringes (m), the laser wavelength (λ), and the angle of incidence of the laser beam (θ = 4°): (Turner et al 2015;Förstel et al 2016bFörstel et al , 2016cTsegaw et al 2017…”

“…In their experiment they used UV flux of 10 15 photons s −1 cm −2 . However, since electron impact ionization does not present an isomer-selective ionization tool, (Kaiser et al 2015;Abplanalp et al 2016a;Förstel et al 2016b;Tarczay et al 2016) the authors defined this ion signal as a possible link to N-methyl formamide. These considerations reveal that the elucidation of the synthetic pathway to N-methyl formamide in low-temperature interstellar analog ices exposed to ionizing radiation is still in its infancy.…”

Synthesis of the hitherto elusive formylphosphine (HCOPH2) in the interstellar medium – a molecule with an exotic phosphorus peptide bond

“…4 Dedicated laboratory simulation studies mimicking the processing of interstellar ice analog samples containing, for instance, ammonia (NH 3 ), carbon dioxide (CO 2 ), and carbon monoxide (CO) verified peptide bond formation upon exposure of these ices to ionizing radiation. 1,5,6 Surprisingly, the phosphorus peptide moiety (-CO-PH-) as an † Electronic supplementary information (ESI) available. See…”

“…Recent experiments in carbon monoxide-methane, 21 carbon monoxide-ammonia, 6 and carbon monoxide-methanol ices 22 also demonstrate that suprathermal hydrogen atoms react with carbon monoxide forming the formyl radical (HCO). If the formyl radical (HCO) has a favorable recombination geometry with the phosphino radical (PH 2 ), both radicals can recombine without barrier leading to the formation of HCOPH 2 (III) reaction (7) as confirmed by calculations (Table S5 and Fig.…”