He+ and Ar+ reactions with perfluoroalkyl carboxylic acids: Degradation of PFBA and PFOA

Abstract

Products of perfluorobutanoic acid and perfluorooctanoic acid with Ar+He+ are reported. Charge transfer occurs efficiently in all cases, followed by dissipation of the substantial excess energy through dissociation of the PFCA cation. The dominant dissociation channels are either carbon‑carbon bond cleavage along the carbon chain backbone or a concerted HF/CO₂ elimination. Less prevalent channels are loss of the hydrogen atom or a single fluorine atom. As excess reaction energy increases, HF/CO₂ elimination decreases and carbon‑carbon bond cleavage increases. The trend is qualitatively explicable as the simple bond cleavage is energetically dis-preferred but entropically favored.