Hydrolysis Kinetics of Thifensulfuron Methyl in Aqueous Buffer Solutions

Abstract

The hydrolysis of thifensulfuron methyl and thifensulfuron were investigated in buffered aqueous solutions with pH values of 4, 5, 9, and 10. Hydrolysis of thifensulfuron methyl was pH dependent and relatively fast both in acidic and alkaline buffer solutions. In the case of thifensulfuron, hydrolysis rates were of the same order of magnitude as thifensulfuron methyl at acidic pH, but very low at alkaline pH. In acidic solutions, cleavage of the sulfonylurea bridge and O-demethylation of the methoxy group of the triazine ring occurred concurrently. The resulting intermediates gave two parallel reactions: cleavage of the sulfonylurea bridge and opening of the triazine ring. The relative rates of the different hydrolysis pathways were influenced by the pK a of compounds. At alkaline pH, thifensulfuron methyl hydrolyzed to thifensulfuron, which was slowly transformed by cleavage of the sulfonylurea bridge and O-demethylation.

Biodegradation of thifensulfuron-methyl by Ochrobactrum sp. in liquid medium and soil

“…Compound C was identified as thifensulfuron acid 3-{[4-Methoxy-6-methyl-1,3,5-triazin-2-yl)carbamoyl]sulfamoyl}thio-phene-2-carboxylic acid. Compounds B and C have been detected as metabolites of thifensulfuron-methyl in soil, plant and aqueous buffer solutions (Brown et al 1993;Cambon and Bastide 1996;Brown et al 1997). The de-esterification of sulfonylurea herbicides has also been reported in other sulfonylurea herbicides with an ester structure in the aryl ring, such as pyrazosulfuron-methyl (Xu et al 2009;Singh and Singh 2011) and metsulfuron-methyl (Hang et al 2012).…”

Hydrolysis of prosulfuron at pH 5: evidence for a resonance-stabilized triazine cleavage product

“…Other groups of workers have also postulated degradates resulting from triazine ringopening, but these structures were never conÐrmed by isolation and conÐrmation of the isolate structure with the authentic reference standard.4,5 The kinetics of hydrolysis have only recently been described for thifensulfuron and thifensulfuron-methyl. 6 This report outlines the identiÐcation of 3 as well as structural conÐrmation of the hydrolysis degradates resulting from hydrolysis of the sulfonylurea bridge.…”

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).…”