Photodegradation of bensulphuron methyl in aqueous solution

Photodegradation of bensulphuron methyl, (methyl -(4,6-dimethoxypyrimidin-2-carbamoylsulphamoyl)-o-toluate ester) was carried out in aqueous solution under UV light. The rate of photolysis followed first-order kinetics, with a half-life of 31.7 min at λ = 254 nm and 41.3 h at λ ≥ 290 nm, with significant correlation coefficients (0.9898 and 0.9625, respectively). The main photoproducts in distilled water were identified with a diode array detector and mass spectrometry. The results indicate that different reaction pathways are followed: cleavage of the sulphonylurea bridge, desulphonylation, which can proceed either by a carbon-sulphur cleavage or a nitrogen-sulphur cleavage and contraction of the sulphonylurea bridge. A mechanism which accounts for the formation of the photoproducts is proposed