Gas Phase Thermochemistry for Perfluoroalkyl Carboxylic Acids
September 16, 2025 - Bradley Welch, Narasimhan Loganathan and Angela K. Wilson
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Perfluorinated species have become ubiquitous due to their desirable industrial
properties including thermal and chemical stability, water resistance, and stain resistance.
Despite their utility and widespread use, a number of PFAS have been identified as significant
environmental contaminants posing health hazards. Much of the current studies are targeted to
understand the fate and distribution of PFAS in water and solid interfaces. In contrast, the
current insight into the thermodynamic properties of PFAS is minimal but play a critical role
for modeling their reactions. In this study, the thermodynamic energies of perfluoroalkanoic
acids (CnF2n+1OOH) have been predicted. The correlation consistent Composite Approach
(ccCA) and coupled-cluster singles, doubles, with triple excitation (CCSD(T)) methods have
been utilized to determine enthalpies of formation and Gibbs free energies including
corrections for the conformational ensemble at 298 K. In addition, density fitted and local
natural orbital coupled cluster approaches have been used to allow for the evaluation of larger
PFAS with the ccCA composite. Thermodynamic predictions made using DFT(B3LYP) have
also been evaluated in comparison to ccCA and CCSD(T) energetics due to its widespread usage in computing thermochemical
properties.
