Substituent Effects on the Direct Photolysis of Benzotrifluoride Derivatives

The chemical class of benzotrifluoride derivatives is widely used in active ingredients of various commercial products, such as pharmaceuticals, pesticides, herbicides, and crop protection agents. Past studies have shown that some benzotrifluorides are not stable under UV irradiation in water and convert into benzoic acids due to C-F bond hydrolysis. It was also observed, but never systematically studied, that the ring substituents play an important role on the direct photochemical reactivity of the CF3 moiety. In the present work, we explore the structure-reactivity relationship between ring substituent and direct photodefluorination for 16 different substituents, by determining fluoride production rates, quantum yields, and half-lives, and found that strong electron-donating groups enhance the reactivity toward hydrolysis. In addition, flufenamic acid, travoprost, dutasteride, cyflumetofen, flutoanil, and teriflunomide were also examined, finding that their direct photochemical reactivity could be qualitatively predicted based on their ring substituents. We provide here a tool to evaluate the environmental persistence of benzotrifluoride contaminants, as well as to design more photodegradable new active ingredients.