Kinetics and Hydrolysis Mechanism of Triasulfuron

Abstract

The hydrolysis of the sulfonylurea herbicide triasulfuron [(2-(2-chloroethoxy)-N-[[4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide] was studied in aqueous buffers of pH values 2, 3, 4, 5, 6, 7, and 9. The reaction was of first-order and pH-dependent. Triasulfuron was more persistent in neutral or weakly basic than in acidic solution. Five metabolites have been isolated and identified. At all pH values studied, the primary pathway of degradation was the cleavage of the sulfonylurea bridge. However, minor degradation pathways have also been observed like O-demethylation and opening of the triazine ring. The product distribution was pH-dependent. Keywords: Sulfonylureas; herbicides; triasulfuron; hydrolysis; degradation

Application of coupled liquid chromatography–mass spectrometry in hydrolysis studies of the herbicide ethametsulfuron-methyl

“…This implied an increase in degradation rate when pH values were increased in alkaline buffers. Similar results have been observed for other sulfonylurea herbicides [17][18][19]. The significantly larger rate of alkaline hydrolysis of ethametsulfuron-methyl than that in neutral water may be attributed to the base-catalyzed reaction involving hydroxyl ion attack on the bridge carbonyl.…”

Identification of photoproducts from imazosulfuron by HPLC

“…aryl sulfonamide and amino heterocyclic portions of the molecule (Hay, 1990;Sabadie, 1990;Cambon and Bastide, 1996;Vicari et al, 1996;Braschi et al, 1997Braschi et al, , 2000Bray et al, 1997;Morrica et al, 2001). In additon to acidic hydrolysis, some sulfonylurea herbicides are also subjected to hydrolytic degradation under alkaline conditions (Vicari et al, 1996;Cambon and Bastide, 1996;Braschi et al, 1997Braschi et al, , 2000.…”

“…In additon to acidic hydrolysis, some sulfonylurea herbicides are also subjected to hydrolytic degradation under alkaline conditions (Vicari et al, 1996;Cambon and Bastide, 1996;Braschi et al, 1997Braschi et al, , 2000. Other herbicides also degraded through bridge contraction and rearrangement (Schneiders et al, 1993;Saha and Kulshrestha, 2002).…”

Adsorption and Degradation of Triasulfuron on Homoionic Montmorillonites

“…At the pH values of the Caand Na-rich montmorillonite suspensions (6.8 and 7.1, respectively) the herbicide is in anionic form and therefore has negligible affinity for the negative surfaces of the clay. On the other hand, triasulfuron degrades very slowly (t~ = 492 d; Braschi et al, 1997) at pH 7. This finding explains the lack of metabolites after 16 d in the Ca-and Na-rich montmorillonite aqueous suspensions.…”

“…The purity was checked by high performance chromatography (HPLC). The triasulfuron metabolites (Figure 1) AMMT, CBSA, CHMT, CBAT, and 2-amino-4-hydroxy-6-methyltriazine (AHMT) were obtained according to the procedure described by Braschi et al (1997). The structures of triasulfuron and its metabolites are given in Figure 1.…”