Fluorinated Photoproduct Formation from Photolysis of Fluorinated Pharmaceuticals and Phenols

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Fluorinated Photoproduct Formation from Photolysis of Fluorinated Pharmaceuticals and Phenols

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2020-08

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Use of fluorine has increased since its first use in 1957 due to its ability to change the physiochemical properties of compounds, including lipophilicity, solubility, conformation, pKa, and metabolic stability. Common fluorine motifs include: -CF3, -CF2, and -CF groups bonded directly onto an aromatic (Ar-CF3 and Ar-F) or pyrazole rings (Py-CF3). Photolysis of these compounds is a potential source of new fluorinated compounds into the environment. With potential toxicity of organofluorine products, such as fluoroacetic acid, monitoring of product formation during photolysis of various fluorinated motifs is needed. To determine fluorinated products, selected pharmaceuticals with the Ar-CF3, Ar-F, and Py-CF3 motifs were subjected to photolysis in four aqueous conditions: pH 7, pH 10, 1 mM H2O2 at pH 7 to form •OH, and 0.5 mM SO32- at pH 10 to form eaq-. Additionally, 2-, 3-, and 4-trifuoromethylphenol (TFMP) and fluorophenol (FP) were used as Ar-CF3 and Ar-F model compounds, respectively. These model compounds were subjected to photolysis to further study product formation from these fluorine motifs, as well as determine if ring placement influences product formation. Product identification and fluorine quantification by 19F-NMR on a 600 MHz magnet equipped with a 5 mm cryoprobe were conducted. Rate constants of parent compound loss were monitored on an HPLC. All Ar-F model compounds only produced fluoride. The three Ar-CF3 model compounds led to different organofluorine products based on motif placement as well as reaction conditions. Trifluoroacetic acid (TFA) was only produced by 4-TFMP, suggesting ring placement is important for TFA formation. TFA was also found to form from fluoxetine, matching the 4-TFMP model compound. Sitagliptin formed fluoride and followed the trend of the Ar-F model compounds except when the pH was above the pKa of the molecule.

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University of Minnesota M.S. thesis. August 2020. Major: Civil Engineering. Advisor: William Arnold. 1 computer file (PDF); xii, 129 pages.

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Whiting, Quinn. (2020). Fluorinated Photoproduct Formation from Photolysis of Fluorinated Pharmaceuticals and Phenols. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/224900.

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