C₃H₈O₂ Isomers: Insights into Potential Interstellar Species

2-Methoxyethanol, with a formula C₃H₈O_2, was recently identified in the massive protocluster NGC 6334I. However, its structural isomers, 1,2-propanediol and 1,3-propanediol, remain undetected despite extensive searches in the Sgr B2 region. In this study, we explored the potential energy surface of the C₃H₈O₂ system using CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ calculations, identifying 11 species, with the geminal diols 2,2-propanediol and 1,1-propanediol as the most stable forms. We examined the gas-phase decomposition barrier of these geminal diols and found that 1,1-propanediol is thermodynamically stable at low temperatures (10-150 K). C₃H₈O₂ isomers with energies below 30 kcal/mol are relevant to the ISM, as they have been identified or tentatively detected in irradiation experiments of ice analogs of CO, H₂O, and CH₃OH.