Photochemical isomerization of fluazifop-butyl

Fluazifop-butyl, butyl (RS)-2-[4-(5-trifluoromethyl-2-pyridyloxy)-phenoxy]propionate, as a thin film on glass, was photo-rearranged by ultraviolet irradiation at 254 nm to the isomer, butyl (RS)-2-[4-hydroxy-3-(5-trifluoromethyl-2-pyridyl)phenoxy]propionate. The reaction followed first-order kinetics. A mechanism that accounts for the formation of this product is proposed.