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.