A theoretical study on the pyrolysis of perfluorobutanoic acid as a model compound for perfluoroalkyl acids

The potential energy surface is mapped out for all plausible reactions in the self-decomposition of perfluorobutanoic acid (CF₃CF₂CF₂COOH) as a model compound for the notoriously toxic and bio-accumulative perfluoroalkyl acids. Initial decomposition of perfluorobutanoic acid is found to be controlled by HF elimination and the formation of an α-lactone intermediate. The fate of this intermediate is predicted to be dominated by two competing channels, namely formation of pentafluoropropanoyl fluoride (CF₃CF₂COF) and the closed-shell singlet CF₃CF₂CF:. Direct elimination of CO₂ through decarboxylation is found to be retarded by strong hyperconjugation effects induced by fluorine atoms on the carbon chain. The results presented herein provide insightful information towards a comprehensive understanding of the decomposition of perfluoroalkyl acids in thermal systems.