pyrazosulfuron-ethyl
Common name: pyrazosulfuron-ethyl
IUPAC name: ethyl 5-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)-1-methylpyrazole-4-carboxylate
Chemical Abstracts name: ethyl 5-[[[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]-1-methyl-1H-pyrazole-4-carboxylate
CAS RN: [93697-74-6]
pyrazosulfuron
Common name: pyrazosulfuron
IUPAC name: 5-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)-1-methylpyrazole-4-carboxylic acid
Chemical Abstracts name: 5-[[[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]-1-methyl-1H-pyrazole-4-carboxylic acid
CAS RN: [98389-04-9]
PHYSICAL CHEMISTRY
pyrazosulfuron-ethyl
Mol. wt.: 414.4; M.f.: C14H18N6O7S; Form: Colourless crystals. M.p.: 177.8-179.5 °C. V.p.: 4.2x10-5 mPa (25 ºC). KOW: logP = 1.3 (unstated pH). S.g./density: 1.46 (20 ºC). Solubility: In water 9.96 mg/l (20 ºC). In methanol 4.32, hexane 0.0185, benzene 15.6, chloroform 200, acetone 33.7 (all in g/l, 20 ºC). Stability: Stable at 50 ºC for 6 months. Relatively stable at pH 7. Unstable in acidic or alkaline media. pKa: 3.7
pyrazosulfuron
Mol. wt.: 386.3; M.f.: C12H14N6O7S
APPLICATIONS
pyrazosulfuron-ethyl
Biochemistry: Branched chain amino acid synthesis (ALS or AHAS) inhibitor. Acts by inhibiting biosynthesis of the essential amino acids valine and isoleucine, hence stopping cell division and plant growth. Selectivity derives from rapid metabolism (demethylation of methoxy group) in the crop.
Mode of action: Systemic herbicide, absorbed by roots and/or leaves and translocated to the meristems.
Uses: Control of annual and perennial broad-leaved weeds and sedges, pre- or post-emergence in wet-sown and transplanted rice crops, at 15-30 g/ha.
Formulation types: GR; SC; WG; WP.
MAMMALIAN TOXICOLOGY
pyrazosulfuron-ethyl
Oral: Acute oral LD50 for rats and mice >5000 mg/kg.
Skin and eye: Acute percutaneous LD50 for rats >2000 mg/kg. Non-irritating to skin and eyes (rabbits). Non-sensitising to skin (guinea pigs).
Inhalation: LC50 for rats >3.9 mg/l air.
NOEL: (78 w) for mice 4.3 mg/kg daily.
ADI: 0.043 mg/kg.
Other: Non-mutagenic in the Ames test. Non-teratogenic in rats and rabbits.
Toxicity class: WHO (a.i.) III (Table 5)
ECOTOXICOLOGY
pyrazosulfuron-ethyl
Birds: Acute oral LD50 for bobwhite quail >2250 mg/kg.
Fish: LC50 (96 h) for rainbow trout and bluegill sunfish >180 mg/l; (48 h) for carp >30 mg/l.
Daphnia: TLm (3 h) >40 ppm.
Algae: I50 for green algae (Scenedesmus acutus) 1 ppm.
Bees: LD50 (contact) >100 ug/bee.
ENVIRONMENTAL FATE
pyrazosulfuron-ethyl
Animals: In rats, after 48 h, 80% of applied pyrazosulfuron-ethyl is excreted in urine and faeces. The major metabolic reaction is demethylation of the methoxy group.
Soil/Environment: In soil, DT50 <15 d. In water, DT50 in buffer solution (pH 7), paddy fields or river water are c. 28 d.
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