Use of fluorine in agrochemical and pharmaceutical design has increased since the first fluorinated pharmaceutical came to market in 1957. Fluorine changes the physical properties, including lipophilicity, solubility, conformation, pKa, and metabolic stability of compounds, making its use appealing. Motifs of fluorine in common pharmaceuticals and agrochemicals include: -CF3 and -F groups bonded directly onto an aromatic or pyrazole ring, -CxHyFz aliphatic groups, and -SFz groups. Photolysis of these compounds is a potential source of new fluorinated compounds into the environment. Depending on the chemical structure and fluorine motif, fluoride and/or other organic fluorine compounds are produced and released into surface waters. With the potential of organic fluorine products, such as fluoroacetic acid, monitoring of product formation during photolysis of various fluorinated motif types is needed. To determine fluorinated products, selected pharmaceuticals and agrochemicals with varying fluorine motifs were subjected to photolysis in four aqueous conditions: pH 7, pH 10, 250 µM H2O2 at pH 7 to form hydroxyl radicals, and 1 mM sulfite at pH 10 to form e-aq. Model compounds (fluorinated phenols and trifluoromethylphenols)l were also subjected to photolysis to determine if ring placement varies product formation. Product identification and fluorine quantificaiton was conducted using a 600 MHz 19F-NMR and complemented by LC-HRMS, and rates of parent compound loss were monitored on an HPLC. Preliminary results suggest that fluoride is one of the most common products, but certain motifs show the formation of trifluoroacetic acid and other organic fluorine molecules. Results will help the design of fluorinated compounds to have the same functionality with the forethought of reducing harmful photoproducts.

Fluorinated photoproduct formation from photolysis of pharmaceuticals and agrochemicals

ACS Spring Meeting 2021

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