Atmospheric Fate of a New Polyfluoroalkyl Building Block, C₃F₇OCHFCF₂SCH₂CH₂OH

Many per- and polyfluoroalkyl substances (PFAS) have been regulated or phased-out of usage due to concerns about persistence, bioaccumulation potential, and toxicity. We investigated the atmospheric fate of a new polyfluorinated alcohol 2-(1,1,2-trifluoro-2-heptafluoropropyloxy-ethylsulfanyl)-ethanol (C₃F₇OCHFCF₂SCH₂CH₂OH, abbreviated FESOH) by assessing the kinetics and products of the gas-phase reaction of FESOH with chlorine atoms and hydroxyl radicals. Experiments performed in a stainless-steel chamber interfaced to an FTIR were used to determine reaction kinetics and gas-phase products. We report reaction rate constants of k(Cl + FESOH) = (1.5 ± 0.6) × 10^-11 cm³ molecule^-1 s^-1 and k(OH + FESOH) = (4.2 ± 2.0) × 10^-12 cm³ molecule^-1 s^-1. This leads to a calculated FESOH gas-phase lifetime of 2.8 ± 1.3 days with respect to reaction with OH, assuming [OH] = 10⁶ molecule¹ cm^-3. Gas-phase products of FESOH oxidation included at least two aldehydes, likely C₃F₇OCHFCF₂SCH₂C(O)H and C₃F₇OCHFCF₂SC(O)H, and secondary products including COF₂, SO₂ and C₃F₇OC(O)F. Additional gas-phase experiments performed in a Teflon chamber were used to assess aqueous products by collecting gaseous samples offline into an aqueous sink prior to analysis with ultrahigh performance liquid chromatography-tandem mass spectrometry, resulting in four acidic products: C₃F₇OCHFCF₂SCH₂C(O)OH, C₃F₇OCHFCF₂S(O)(O)OH, C₃F₇OCHFC(O)OH, and perfluoropropanoic acid (C₂F₅C(O)OH).