| Abstract
| - Vapor pressure and aqueous solubility are important parameters used to estimate the potential for transportof chemical substances in the atmosphere. For fluorotelomer alcohols (FTOHs), currently under scrutiny byenvironmental scientists as potential precursors of persistent perfluorocarboxylates (PFCAs), vapor pressureis the more significant property since these compounds are only very sparingly soluble in water. We havemeasured the vapor pressures of a homologous series of fluorotelomer alcohols, F(CF2CF2)nCH2CH2OH(n = 2−5), in the temperature range 21−250 °C by three independent methods: (a) a method suitable forvery low vapor pressures at ambient temperatures (gas-saturation method), (b) an improved boiling pointmethod at controlled pressures (Scott method), and (c) a novel method, requiring milligram quantities ofsubstance, based on gas-phase NMR, a technique largely unfamiliar to chemists and holding promise forstudies of relevance to environmental chemistry. The concordant values obtained indicate that recently publishedvapor pressure data overestimate the vapor pressure at ambient temperature, and therefore the volatility, ofthis series of fluorinated compounds. It was suggested that substantial intramolecular −O−H···F− hydrogenbonding between the hydroxylic proton and the two fluorines next to the ethanol moiety was responsible fortheir putative high volatility. Therefore, we have used gas-phase NMR, gas-phase FTIR, 2D NMR heteronuclearOverhauser effect measurements, and high-level ab initio computations to investigate the intramolecularhydrogen bonding in fluorotelomer alcohols. Our studies unequivocally show that hydrogen bonding of thistype is not significant and cannot contribute to and cause unusual volatility. The substantially lower vaporpressure at ambient temperatures than previously reported resulting from our work is important in developinga valid understanding of the environmental transport behavior of this class of compounds.
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