Absorption Reveals and Hydrogen Addition Explains New Interstellar Aldehydes: Propenal and Propanal

摘要

Large molecules found to date in interstellar clouds suggest a grain chemistry that favors aldehyde production. Consistent with this, we (Hollis et al. 2000) successfully detected interstellar glycolaldehyde (CH2OHCHO) and suggested that it might result from polymerization of two formaldehyde molecules (H2CO) analogous to the early stage of the sugar synthesis (formose) reaction studied in the laboratory by investigators of prebiotic chemistry. Additionally, laboratory experiments have shown that subjecting cometary ice analogs to ionizing radiation at approx. 15 K results in solid-phase hydrogen addition reactions. The combination of the prevalence of interstellar aldehydes and the likelihood of subsequent hydrogen addition reactions with aldehydes prompted a successful search for interstellar ethylene glycol. The detection of interstellar ethylene glycol, which differs in constituent atoms of glycolaldehyde by two hydrogen atoms, suggested that ethylene glycol is the product of two successive low-temperature hydrogen addition reactions with glycolaldehyde on grain surfaces or in grain ice mantles.