Partitioning of Fluoroalcohols and Their Environmental Implications

Fluoroalcohols are a class of alcohols that have fluorine atoms in place of the hydrogens on the alkyl chain and are found in many industrial products produced throughout the world. Fluoroalcohols can be oxidized in the environment to form perfluorooctanoic acid (PFOA), a persistent organic pollutant. Therefore, it is important to understand how fluorination affects the bioavailability of these compounds, especially in places where bioaccumulation is becoming a problem, such as the Arctic. The octanol-water partition coefficient is an accurate and widely-accepted way to compare the bioavailability of various chemicals, and can be found both experimentally and through simulation.

            Molecular simulations using the OPLS-AA force field parameters and the molecular dynamics simulation engine NAMD (ver. 2.9) were performed on fluoroalcohols of varying chain length from perfluoromethanol to perfluorooctanol. Free energy perturbation was used to determine the free energies of solvation (in 1-octanol) and hydration.  Once known, these free energies were used to determine the octanol-water partition coefficients. Simulations showed that fluoroalcohols tend to solvate better in 1-octanol and hydrate worse in water. The calculated octanol-water partition coefficient for fluoroalcohols tended to increase with chain length and number of fluorine atoms, which by the guidelines of AC-BAP (Artic Contamination and Bioaccumulation Potential) means that heavier fluoroalcohols are likely to become persistent contaminants and are more likely to be oxidized into persistent organic pollutants.