Oxime ether photobromination in a photomicroreactor: Process parameters and kinetic modeling

Photobromination reaction of oxime ether (OE) to brominated oxime ether (BOE) is an important process for the synthesis of trifloxystrobin in the fungicide industry. Herein, continuous synthesis of BOE in photomicroreactors was performed. Initially, an investigation was carried out to study the effects of various parameters, including mixing performance, molar ratios, solvents, incident photon flux, and temperature, on the photobromination process. Moreover, a kinetic model was established, and the activation energies for the main and side reactions were determined. The relationship between the reaction rate constant and light flux was illuminated. Transition states and energy changes in the bromination process were analyzed using density functional theory calculation. Remarkably, an 83.1% yield of BOE was achieved in the photomicroreactor and the required reaction time was reduced to approximately 1/10 of the batch reactor. This work was of crucial theoretical significance and practical value for better understanding of photobromination processes and parameter optimization.