Atmospheric Reactivity and Environmental Implications of 2‑Propoxyethanol: Kinetic and Mechanistic Insights into Its Oxidation by OH, NO3, and Cl.

Hydroxyethers (HEs) are widely used oxygenated volatile organic compounds (OVOCs). Among them, 2-propoxyethanol (CH3CH2CH2OCH2CH2OH, 2-PE) is of particular interest due to its extensive use and the limited mechanistic information available regarding its atmospheric degradation. These characteristics place 2-PE as a compound of emerging environmental interest and motivate a detailed investigation of its reactivity with key atmospheric oxidants. This compound is commonly used as a solvent and emulsifying agent for hydrophobic substances, and it has been proposed as a biodiesel additive. Once released into the atmosphere, 2-PE undergoes degradation processes mainly by reactions with oxidants (OH and NO3 radicals, Cl atoms). This study provides a kinetic and mechanistic investigation of the atmospheric degradation of 2-PE using FTIR (Fourier transform infrared spectroscopy) and GC-MSTOF (gas chromatography/mass spectrometry time of flight). Rate coefficients at ambient temperature and pressure, were (units cm3 molecule-1 s-1): (1.99 ± 0.12) × 10-10, (2.54 ± 0.15) × 10-11 and (7.20 ± 0.53) × 10-15 for Cl, OH• and NO3 • reactions, respectively. Detected products include formaldehyde, acetaldehyde, propyl formate, 2-hydroxyethyl formate and 2-hydroxyethyl propanoate, quantified by FTIR, and nitrated compounds detected in the presence of NO x . Based on product distributions and structure-reactivity relationships, two predominant reaction pathways are proposed, both initiated by the oxidant attack on the -CH2- group adjacent to the ether. Atmospheric lifetimes indicate that OH• reaction dominates the 2-PE removal. Estimated GWP and ozone formation indices confirm that 2-propoxyethanol is a short-lived VOC with limited direct climate impact, while providing a basis for comparison with structurally related glycol ethers and other VOCs.