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

Frigge, Robert, Zhu, Cheng, Turner, Andrew M., Abplanalp, Matthew J., Sun, Bing-Jian, Huang, Ya-Syuan, Chang, Agnes H. H., Kaiser, Ralf I.
Chemical communications 2018 v.54 no.72 pp. 10152-10155
carbon monoxide, chemical reactions, free radicals, gases, hydrogen, ionizing radiation, isomers, mass spectrometry, phosphine, phosphorus
The formylphosphine (HCOPH₂) molecule was detected in the gas phase via isomer selective photoionization reflectron time-of-flight mass spectrometry (PI-ReTOF-MS). Synthesized in carbon monoxide (CO)–phosphine ices (PH₃) exposed to ionizing radiation, the formation mechanism involves an initial phosphorus–hydrogen bond rupture in phosphine yielding the phosphino radical (PH₂) along with atomic hydrogen, addition of the suprathermal hydrogen atom to carbon monoxide leading to the formyl radical (HCO), and recombination of both radicals to formylphosphine (HCOPH₂). This molecule represents the isovalent counterpart of the ubiquitous interstellar formamide (HCONH₂). This study provides a fundamental framework to explore the synthesis and stability of the simplest isovalent counterpart of interstellar formamide (HCONH₂) and suggests that formylphosphine (HCOPH₂) should be detectable in the interstellar medium eventually providing a missing link between phosphorus-bearing complex organic molecules detected in the interstellar medium and on comet 67P/Churyumov–Gerasimenko.