Photolysis and hydrolysis of rimsulfuron

Abstract

The degradation in the liquid phase of rimsulfuron and its commercial 250 g kg−1 WG formulation (Titus®) was investigated. Photolysis reactions were carried out at 25 °C by a high‐pressure mercury arc (Hg‐UV) and a solar simulator (Suntest), while the hydrolysis rate was determined by keeping aqueous buffered samples in the dark. The effects of solvent and water pH on reaction kinetics were studied, and the results compared to literature data. Photoreactions of the commercial product in organic solvents were faster than pure rimsulfuron. Under simulated sunlight in water, the half‐life for the photolysis reaction ranged from one to nine days at pH 5 and 9, respectively. The hydrolysis rate was as high as the photolysis rate, but decreased on increasing water pH. The main metabolite identified in neutral and alkaline conditions as well as in acetonitrile was N‐[(3‐ethylsulfonyl)‐2‐pyridinyl]‐4,6‐dimethoxy‐2‐pyridinamine, while N‐(4,6‐dimethoxy‐2‐pyrimidinyl)‐N‐[(3‐(ethylsulfonyl)‐2‐pyridinyl)]urea and minor metabolites prevailed in acidic conditions. © 1999 Society of Chemical Industry

Photodegradation of Flucetosulfuron, a Sulfonylurea-Based Herbicide in the Aqueous Media Is Influenced by Ultraviolet Irradiation

“…The compound is also being found during flucetosulfuron metabolism in artificial gastrointestinal juice [ 29 ]. This phenomenon has also been reported in the metabolism of similar compounds such as sulfosulfuron [ 30 ], imazosulfuron [ 31 ] and rimsulfuron [ 32 ]. The second isolated compound M 2 was eluted with solvent composition, hexane–ethyl acetate (70:30) with a single spot in TLC.…”

Reactivity of rimsulfuron in newly formed inclusion combinations by using cyclodextrin and zeolite

“…Using 14 C-labelled rimsulfuron, Schneiders et al [12] showed that its degradation in aqueous solutions and in the soil environment does not depend on irradiation under natural sunlight, though it undergoes hydrolysis reactions. Different results were achieved in a previous study, in which Scrano et al [13] stated that the half-life of the photolysis reaction under simulated sunlight in water ranges from 1 to 9 days at pH 5 and 9, respectively, and the hydrolysis rate is as high as the photolysis rate, and decreases with increasing solution pH. The main metabolite identified in neutral and alkaline conditions as well as in the acetonitrile was compound 3, N-[(3-ethylsulfonyl)-2-pyridinyl]-4,6-dimethoxy-2-pyridineamine; while compound 2, N-(4,6-dimethoxy-2-pyrimidinyl)-N-[(3-(ethylsulfonyl)-2-pyridinyl)] urea (resulting from the intramolecular contraction of the sulfonylurea bridge), and minor metabolites prevailed in acidic conditions (figure 1) [12,13].…”

“…The metabolites indicated in figure 1 as compounds 2 and 4 were not found in any sample. On account of its low stability, the impossibility of recognizing compound 2, which was previously found only in acidic environments [12,13], was not surprising. In the case of compound 4, we suppose that it might have been the final product of the photolysis of the newly identified compound 7, which in our experimental conditions was not transformed any further.…”

Effect of soil organic matter destruction on sorption and photolysis rate of rimsulphuron

“…Calibration and working solutions of AI were prepared when used by dilution from stock solution. The choice of acetonitrile as a suitable solvent for our experiments follows the need for a better comprehension of the photochemical and spectroscopic behaviour of the organic compound [5], avoiding as much as possible the undesirable hydrolysis reaction [1,3]. A soil sampled from Sellata Mountain in the south of Italy, and characterized by a high content of organic matter (OM), was selected as the sorption medium.…”

“…[2]. Scrano et al [3] showed that, under simulated sunlight in water, the halflife of photolysis reaction ranged from 1 to 9 days at pH 5 and 9, respectively. The hydrolysis rate was as high as the photolysis rate, and decreased on diminishing the pH values of the solution.…”