The oxidative cyclization reaction of 5-chloro-2-nitroaniline via sodium hypochlorite to yield 5-chloro-benzofuroxan is investigated by the hybrid density functional theory (DFT) B3LYP/6-31G(d,p) method. Solvent effects are estimated with the polarizable continuum model (PCM) model to optimize structures. Two possible stepwise pathways are proposed: (1) oxidization, hydrogen transfer, dehydration and cyclization, (2) hydrogen transfer, hydrogen rotation in imine, oxidation, dehydration, and cyclization|the former is a favored process with the lower activation barrier. Our results show that the reaction in very nonpolar solutions such as CCl₄ has a lower activation barrier than for polar solutions such as ethanol. Compared with the reaction of 2-nitroaniline via sodium hypochlorite, title reaction with the similar mechanism is more favored because of the lower activation barrier at the rate-determining step (RDS).

Key words: benzofuroxan, furaxan, 5-chloride-2-nitroaniline, sodium hypochlorite