An Experimental and Theoretical Investigation into the Formation of Ketene (H₂CCO) and Ethynol (HCCOH) in Interstellar Analog Ices

Abstract

The formation of isomers of C2H2O—ketene (H2CCO), ethynol (HCCOH), and oxirene (c-CHCHO)—was investigated in interstellar ice analogs composed of carbon monoxide and water. Using tunable photoionization time-of-flight mass spectrometry to selectively ionize the isomer of interest, ketene and ethynol were detected as reaction products, but oxirene remains elusive. These findings demonstrate that organic compounds that are precursors to complex organic molecules can form without an organic source of carbon. Furthermore, we report the first plausible detection of ethynol in astrophysically relevant ices. These investigations were supported by theoretical calculations describing reaction energies, pathways, ionization energies, and harmonic frequencies.

Formation of CO, CH4, H2CO and CH3CHO through the H2CCO + H surface reaction under interstellar conditions

“…In recent years, a number of observational investigations and theoretical and experimental studies have been carried out focusing on the formation and transportation routes of ketene molecules. [5][6][7][8][9][10] Ketene was detected in space for the first time by Turner et al in 1977 11 in the dense molecular cloud Sagittarius B2. Then, many astronomical observations have reported its detection in massive hot cores and giant molecular clouds such as Orion KL and TMC-1, 12,13 in the gas phase of translucent clouds (CB 17, CB 24, and CB 228), 14 toward the prestellar core L1689B, extragalactic source PKS 1830-211, and in several deeply embedded protostars (AFGL 989, WL 22, NGC 6334I, and NGC 7538 I1).…”

Interstellar Enolization‐Acetaldehyde (CH3CHO) and Vinyl Alcohol (H2CCH(OH)) as a Case Study

“…Scheme 1 depicts tautomer pairs detected after the processing of interstellar analog ices in the laboratory. Ketene (H 2 CCO) and its ynol, ethynol (HCCOH), have been detected in processed carbon monoxide (CO) – water (H 2 O) ice mixtures, [13] whereas carbon monoxide and ethane (C 2 H 6 ) mixtures yielded propanal (CH 3 CH 2 CHO) and 1‐propenol (CH 3 CH=CHOH) [14] . Acetaldehyde and vinyl alcohol were detected in ices containing carbon monoxide and methane (CH 4 ) [14] or carbon dioxide (CO 2 ) and ethylene (C 2 H 4 ), [15] and after UV photolysis and proton irradiation of ices containing acetylene (C 2 H 2 ) and water (H 2 O) [16] .…”

Bottom-Up Synthesis of 1,1-Ethenediol (H2CC(OH)2)─The Simplest Unsaturated Geminal Diol─In Interstellar Analogue Ices

“…Thus, far, the only detected tautomer pair in space is acetaldehyde (CH 3 CHO)–vinyl alcohol (H 2 CCHOH) . In contrast, enols were detected in laboratory simulation studies, such as the tautomer pairs ketene (H 2 CCO)–ethynol (HCCOH), the “prebiotic” pairs pyruvic acid (CH 3 COCOOH)–2-hydroxyacrylic acid (CH 2 C­(OH)­COOH), and glycolaldehyde (HOCH 2 CHO)–1,2-ethenediol (HOHCCHOH) . The detection of 1,2-ethenediol formed in a bottom up synthesis from readily available carbon monoxide and methanol interstellar ice precursors could explain the formation of complex sugars by a formose reaction in cometary analogue ices without a catalyzing mineral .…”