Atmospheric Fate of a New Polyfluoroalkyl Building Block, C₃F₇OCHFCF₂SCH₂CH₂OH

Abstract

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).

In Vivo Transformation of a Novel Polyfluoroether Surfactant

“…To our knowledge this is the first report of fluorinated thioethers being oxidized to the sulfonate in a rat. The products observed in the present study are in agreement with those observed in an atmospheric oxidation study of FESOH by Joudan et al (2021), while differing from the results of the aerobic microbial biodegradation study on diFESOS, FESOH, and FESCA by the same authors. Specifically, the 2H 3:2 PFECA metabolite was observed via microbial degradation, rather than 2H 3:2 PFESA (Joudan et al, submitted).…”

Avoiding Regrettable Replacements: Can the Introduction of Novel Functional Groups Move PFAS from Recalcitrant to Reactive?

“…To do so, a relative-rate experiment was first conducted with FESOH using 1,3,5,trimethylbenzene, m-xylene, and toluene as reference compounds to confirm and compare to the kinetics result from Joudan et al on FESOH. 11 The room temperature OH rate constants for these reference compounds are all well-known. 23 The production of OH radicals ( • OH) occurred through the photolysis of hydrogen peroxide with UVB lamps with emissions centered at 310 nm…”

“…Due to the lack of standards available for many of the transformation products, a comparison of intensity following normalization to the reagent ion and the initial mixing ratio of the dosed alcohol is reported. This strategy is limited to qualitative data due to the different sensitivities of the products in the CIMS; however 11 i.e., FESAL, FESCA, 2H-3:2 PFECA, 2H-3:2 PFESA, CHFO, CF 2 O, and SO 2 , in addition to some novel products. Of the major polyfluorinated acids observed, 2H-3:2 PFESA and 2H-3:2 PFECA, the carboxylic acid was produced, showing rapid abundant production and subsequent loss over the experimental time period.…”

“…FESOH and its congeners offer an illustration of how the functionalization of highly fluorinated compounds can facilitate transformation, with FESOH undergoing varying degrees of degradation into short-chain PFAAs, depending on the environmental matrix. − The original work on the atmospheric transformation of FESOH by Joudan et al determined that it reacts faster than its legacy congener 6:2 fluorotelomer alcohol (FTOH), and the resulting terminal products were either 2H-3:2 PFECA or PFPrA. However, the degree to which each unique functional moiety within FESOH played for the reaction rate and extent of breakdown is unknown.…”

Recent Advances in the Synthesis and Transformation of Carbamoyl Fluorides, Fluoroformates, and Their Analogues

“…Atmospheric oxidation of (CF 3 ) 2 CHOCH 2 F ( 250 ) gave (CF 3 ) 2 CHOC(O)F ( 251 ) in a molar yield of 93±6% with CF 3 C(O)CF 3 and HCOF as minor products. In addition, the atmospheric fate of C 3 F 7 OCHFCF 2 S(CH 2 ) 2 OH ( 252 ) was investigated by assessing the kinetics and products of its gas‐phase reactions with •Cl atoms and •OH radicals [75e] . The gas‐phase oxidation of 252 yielded at least two aldehydes, which reacted further to form secondary species such as O=CF 2 , SO 2 , and C 3 F 7 OC(O)F ( 253 ).…”