Vapor Pressures of the Fluorinated Telomer AlcoholsLimitations of Estimation Methods

Abstract

The influence of the unique, physical properties of poly- and perfluorinated chemicals on vapor pressure was investigated. Vapor pressures of a suite of fluorinated telomer alcohols (FTOHs) (CF3(CF2)nCH2CH2OH, where n = 3, 5, 7, or 9) were measured using the boiling point method and ranged from 144 to 992 Pa. Comparison of experimental and literature values indicate that perfluorocarbons (CF3(CF2)nCF3, where n = 0-6) and fluorinated telomer alcohols have vapor pressures equal to or greater than that of their hydrogen analogues. These chemically counterintuitive results can be explained by the unique geometry of poly- and perfluorinated chemicals--in particular the stiff, helical perfluorinated chain and the significant intramolecular hydrogen bonding of the FTOHs. The majority of models investigated for the estimation of vapor pressure did not compensate for this unique geometry and consistently underpredicted the vapor pressures of the FTOHs. Calculation of partitioning constants using both experimental and estimated vapor pressures indicate that both the Antoine and Modified Grain models, and to a lesser degree the Mackay model, are insufficiently accurate for estimating the vapor pressures of the FTOHs, particularly the longer chain FTOHs. Future models should consider parameters such as geometry, strength, and location of intramolecular hydrogen bonds and otherfunction groups in the molecule in order to improve vapor pressure estimation accuracy. It appears likely that the unique molecular geometry of the FTOHs influences not only their vapor pressure but also other physical properties and hence environmental fate and dissemination.

Presence and Partitioning Behavior of Polyfluorinated Iodine Alkanes in Environmental Matrices around a Fluorochemical Manufacturing Plant: Another Possible Source for Perfluorinated Carboxylic Acids?

“…It is possible that the usage of FIAs is higher in this manufacturing plant, or FIAs have higher potential to be volatilized and thus emitted into the environment. This is supported by previous publications which suggested that vapor pressures for perfluorinated chemicals are equal to or greater than those of the analogues with fluorine atoms replaced by hydrogen atoms (29,30).…”

“…The result might partly be explained by their physical-chemical properties, which are related to the partitioning between matrices. Stoichiometric model (33) showed that the calculated vapor pressures ranged from 0.122 (PFDoI) to 20.4 Torr (PFHxI) for the FIAs and 0.095 (PFDoHI) to 2.9 Torr (PFOHI) for the FTIs, which were almost the same as or even higher than the calculated values for FTOHs (0.008 Torr (10:2 FTOH) to 9.94 Torr (4:2 FTOH)) and measured results (1.08 Torr (10:2 FTOH) to 7.44 Torr (4:2 FTOH)) (29). It is widely accepted that chemicals with vapor pressures above 0.1 Torr are usually classified as volatile organic compounds (VOCs) (34) and consequently most of the PFIs can also be considered as neutral volatile fluorinated substances, which would mostly be evaporated from soil or directly emitted into the atmosphere under ambient conditions.…”

Polyfluoroalkyl compounds in the Canadian Arctic atmosphere

“…713 Pa for 6 : 2 FTOH). [34] Longer chain PFCAs (C 10 -C 12 and C 14 ) were quantified in the particle phase, whereas no PFCAs could be detected in the gas phase. If half of the MDL was used for the values which were below the MDL, the particle-associated fraction would range from 76-83 % for the longer chain PFCAs.…”

Highly Fluorous Porphyrins as Model Compounds for Molecule Interferometry

“…In porphyrin 5, the branching occurs in an aliphatic segment, whereas the other four branched structures comprise 1,3,5-trisubstituted benzenes. The series covers a molecular weight range from 2803 (2) to 7553 g mol -1 (7), which is the current mass region of the most-complex interfering particles.…”

“…[7,8] Their volatility originates in their low polarizability and only small van der Waals interactions between the fluorinated chains. Additionally, these structures are chemically stabilized due to the strength of the carbon-fluorine bond.…”