Radical chemistry in atmospheric ice analogs forms persistent trifluoroacetic acid.

Authors

Mason McAnally, Koushik Mondal, Yuheng Luo, Nils W Melbourne, Pooja Chahal, Xilin Bai, Jinghui Lu, Baoyu Song, Xinxuan Wang, Andrew M Turner, Alexandre Bergantini, Souvick Biswas, Rui Sun, Tao Yang, Ralf I Kaiser

Published in

Chemical science. Oct 06, 2026. Epub Oct 06, 2026.

Abstract

Trifluoroacetic acid (TFA, CF₃COOH), the most prevalent per- and polyfluoroalkyl substance (PFAS), is accumulating globally in precipitation, soils, and drinking water, yet its formation remains unresolved. Atmospheric models emphasize gas-phase oxidation of hydrofluorocarbons and hydrofluoroolefins, but measured abundances often exceed predictions, implying missing chemistry. Here, we identify a condensed-phase radical pathway to TFA in cryogenic trifluoromethane/carbon dioxide ice analogs. Energetic processing generates trifluoromethyl (CF₃) and hydroxycarbonyl (HOCO) radicals that undergo barrierless recombination to form TFA. Fourier transform infrared spectroscopy tracks reactive intermediates and carboxylic acid functional groups, while synchrotron vacuum-ultraviolet photoionization reflectron time-of-flight mass spectrometry provides isomer-selective detection of TFA and diagnostic dimer fragments. These results support CF₃-HOCO recombination as a potential condensed-phase route linking fluorocarbon degradation to persistent PFAS formation, highlighting the potential role of ice crystals and cloud particles as chemical reactors in atmospheric fluorine chemistry.

PMID:
42841097
Bibliographic data and abstract were imported from PubMed on 07 Oct 2026.

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