2021MNRAS.507.2632L

Glycolaldehyde, the simplest sugar, is a complex organic molecule detected in many regions of the interstellar medium (ISM). Although its synthetic routes are fairly well known and consistent with many laboratory studies, queries still arise about its reactivity and its role in the complex chemistry of the ISM. This study shows the surface and bulk hydrogenation of glycolaldehyde at 10 K in order to confirm or invalidate the astrophysical models which suggest that CHOCH₂OH would be a precursor of ethylene glycol through hydrogenation processes occurring on the surface of interstellar dust grains. By coupling IR spectroscopy and mass spectrometry, we show that the formation of HOCH₂CH₂OH from CHOCH₂OH + H solid state reaction occurs, supporting the existence of a chemical link between these two organics in the ISM. This work suggests that while CHO + CH₂OH and CH₂OH + CH₂OH radical recombination would lead to CHOCH₂OH and HOCH₂CH₂OH, respectively, the presence of H-atoms in the ISM would be a secondary source to favour ethylene glycol over glycolaldehyde. These results are in good agreement with different astronomical observations which show simultaneous detections of glycolaldehyde and ethylene glycol with an abundance ratio HOCH₂CH₂OH/CHOCH₂OH ranged between 1 and 15.