Sonochemical chloro-oxidation of phenols using HCl–H2O2

The reaction of phenol, 2-nitrophenol, thymol, 1-naphthol and 1-hydroxy-2-naphthoic acid with HCl–H2O2 was carried out in the presence and in the absence of ultrasound. In the presence of ultrasound phenol, 2-nitrophenol and thymol gave only the chlorinated products, while 1-naphthol and 1-hydroxy-2-naphthoic acid gave chlorinated quinones as the major products. The reactions with ultrasound were compared with those without ultrasound.