ULTRASOUND-ASSISTED ANODIC-OXIDATION OF DIURON

Bulk electrolysis of diuron (3-(3,4-dichlorophenyl)-1,1-dimethyl urea) was carried out at a glassy carbon anode with ultrasound in order to avoid a total blockage of the electrode surface by a passivating film. The major oxidation product PI isolated in 23% yield resulted from th e loss of one electron and one proton with formation of a nitrogen rad ical and of the corresponding N-N dimer. Two more compounds P2 and P3 were isolated in 12 and 10% yields. They are suggested to originate fr om an intramolecular Fries rearrangement in dimer P1, i.e. the migrati on of an amide group from a monomeric unit of the dimer to the aromati c ring of the second one, with formation of a dichloro-N, N-dimethyl b enzamide derivative. This rearrangement would be related to a strong a dsorption of the intermediate nitrogen radical. It would occur at the positively charged electrode surface concomitantly with the N-N bondin g formation. Several non-identified minor compounds were generated, wh ich could involve multi-electron oxidation processes, since the overal l oxidation process of diuron required more than one electron. (C) 199 8 Elsevier Science S.A. All rights reserved.