The Ethanol Tree: Gas-Phase Formation Routes for Glycolaldehyde, Its Isomer Acetic Acid and Formic Acid

In the field of astro- and prebiotic chemistry, the building blocks of life, which are molecules containing C atoms and composed of more than 6 atoms, are called Complex Organic Molecules (COMB). Their appearances on the early inorganic Earth is therefore one of the major issues faced by researchers interested in the origin of life. In this paper, new insights into the formation of several interstellar species of great relevance in prebiotic chemistry (glycolaldehyde, acetic acid and formic acid) are provided by electronic structure and kinetic calculations. The precursors O(P-3) and both hydroxyethyl radicals ((CH2CH2OH)-C-center dot and (CH3CHOH)-C-center dot) were considered. Two reaction paths were obtained and the resulting rate constants show not only that they are viable in interstellar medium (ISM), but also that when included in an astrochemical model, the obtained abundances for glycolaldehyde match well the observed ones. Unfortunately, in the case of acetic acid and formic acid, the predicted abundances are found around one order of magnitude higher than the observed ones.