N-Substituted 4-iminocyclohexa-2,5-dienylidenes (λmax = 300 and 405 nm) are detected at pulse end upon laser flash photolysis of aqueous monuron and metobromuron. In oxygenated medium these carbenes are converted into N-substituted iminoquinone-O-oxides (λmax = 300 nm and 460 nm) and in the presence of H-donor molecules into N-substituted anilino radicals (λmax = 430 nm).
