Quantum Tunneling Mediated Low-Temperature Synthesis of Interstellar Hemiacetals

Sugars and sugar-related molecules are ubiquitous incarbonaceousmeteorites and in star-forming regions, but the underlying mechanismsof their formation have remained largely elusive. Herein, we reportan unconventional synthesis of the hemiacetal, (R/S)-1-methoxyethanol (CH3OCH(OH)CH3), through quantum tunneling mediated reactions in low-temperatureinterstellar model ices composed of acetaldehyde (CH3CHO)and methanol (CH3OH). The detection of racemic 1-methoxyethanolthrough a bottom-up synthesis from simple, abundant precursor moleculeswithin interstellar ices represents a vital starting point to theformation of complex interstellar hemiacetals. Once synthesized, hemiacetalsmay act as possible precursors to interstellar sugars and sugar-relatedmolecules in deep space.