Phototransformation of metoxuron [3-(3-chloro-4-methoxyphenyl)-1,1-dimethylurea] in aqueous solution

UV irradiation of metoxuron in aerated aqueous solution at 254 nm or betwee n 300 and 450 nm led initially to an almost specific photohydrolysis of the C-Cl bond, resulting in the formation of 3-(3-hydroxy-4-methoxyphenyl)-1,1 -dimethylurea (MX3) and hydrogen chloride. The quantum yield was determined to be 0.020 (+/-0.005) in solutions irradiated at 254nm. Five minor photop roducts were also identified, in particular the dihydroxydimethoxybiphenyl derivatives resulting from the phototransformation of MX3. Irradiation incr eased the toxicity of an aqueous solution of metoxuron to the marine bacter ium Vibrio fischeri. (C) 2001 Society of Chemical Industry.