Nicosulfuron: Alcoholysis, Chemical Hydrolysis, and Degradation on Various Minerals

Abstract

Alcoholysis (methanol or ethanol) and hydrolysis (pH ranging from 4 to 11) of the herbicide nicosulfuron at 30 degrees C principally involves the breakdown of the urea part of the molecule. A high yield of the corresponding carbamate was obtained along with aminopyrimidine during alcoholysis. Hydrolysis led to both aminopyrimidine and pyridylsulfonamide. The latter compound may be easily cyclized (pH > or = 7). First-order kinetics describe the rates of alcoholysis and hydrolysis well. The rate constants (0.44 days(-1) for methanolysis) decreased from 0.50 to 0.002 days(-1) as pH increased from 4 to 8, then remained stable under alkaline conditions. In acidic or neutral solution, the hydrolysis path appeared prevalent (> or =70%), whereas in an alkaline medium it decreased when pH increased. The chemical degradation of nicosulfuron on various dry minerals (calcium bentonite, kaolinite, silica gel, H(+) bentonite, montmorillonite K10, and alumina) was investigated at 30 degrees C. The best conditions for the degradation are obtained on acidic minerals after herbicide deposition using the liquid method. Under these conditions an acceptable correlation with pseudo-first-order kinetics was observed, and the major degradation path is similar to that proposed for chemical hydrolysis. Conversely, alumina seemed to favor other unknown degradation processes. The hydrolysis paths of nicosulfuron and rimsulfuron appeared to be different.

Examination of the distribution of nicosulfuron in sunflower plants by matrix‐assisted laser desorption/ionisation mass spectrometry imaging

“…A previous study by Sabadie17 described the formation of breakdown products of nicosulfuron via alcoholysis and hydrolysis. This would potentially lead to a species of aminopyrimidyl structure (Fig.…”

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

“…A compound similar to this product was identified as a hydrolysis product of chlorimuron and nicosulfuron in aqueous solution [25,26].…”

Comportamento do glifosato no solo e deslocamento miscível de atrazina

“…A hidrólise, assim como outros mecanismos de quebra de moléculas, tem sido bastante abordada na literatura (Greenhalgh et al, 1980;Macalady & Wolfe, 1983;Morrica et al, 2001;Sabadie, 2002). Entretanto, o estudo da contribuição de cada processo abiótico na transformação de um pesticida no solo torna-se praticamente impossível, devido à complexidade do sistema.…”

“…Grupos funcionais como ésteres de ácido carboxílico, ésteres de organofosforados, amidas, anilinas, carbamatos, azinas etc., comumente encontrados em muitos pesticidas, são passíveis de sofrer hidrólise (Sabadie, 2002). Os ésteres de ácido carboxílico, por exemplo, estão presentes nos herbicidas 2,4-D; 2,4,5-T e em alguns inseticidas do grupo dos piretróides.…”