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florasulam
Herbicide
HRAC B WSSA 2; triazolopyrimidine
NOMENCLATURE
Common name florasulam (BSI; pa ISO)
IUPAC name 2',6',8-trifluoro-5-methoxy[1,2,4]triazolo[1,5-c]pyrimidine-2-sulfonanilide
Chemical Abstracts name N-(2,6-difluorophenyl)-8-fluoro-5-methoxy[1,2,4]triazolo[1,5-c]pyrimidine-2-sulfonamide
CAS RN [145701-23-1] Development codes DE-570 (Dow)
PHYSICAL CHEMISTRY
Mol. wt. 359.3 M.f. C12H8F3N5O3S M.p. 193.5-230.5 °C (decomp.) V.p. 1 ´ 10-2 mPa (25 °C) KOW logP = -1.22 (pH 7.0) Solubility In water 6.36 g/l (pH 7.0, 20 °C). pKa 4.54
COMMERCIALISATION
History Reported by A. R. Thompson et al. (Proc. Br. Crop Prot. Conf. - Weeds, 1999, 1, 73); see also papers in Proc. 9th IUPAC Int. Congr. Pestic. Chem., London, 1998, 2. Discovered by Dow AgroSciences, and introduced in Belgium in 1999. Manufacturers Dow AgroSciences
APPLICATIONS
Biochemistry Branched chain amino acid (leucine, isoleucine and valine) synthesis (ALS or AHAS) inhibitor. Selectivity in wheat is due to differential metabolism. Mode of action Taken up by root and shoots, and translocated in both xylem and phloem. Uses Herbicide for post-emergence control of broad-leaved weeds, especially Galium aparine, Stellaria media, Polygonum convolvulus, Matricaria spp., and various cruciferae, in cereals and maize, at rates up to 7.5 g/ha. Formulation types SC; SE. Selected products: 'Boxer' (Dow AgroSciences); 'Nikos' (Dow AgroSciences); 'Primus' (Dow AgroSciences); mixtures: 'Frontline' (+ MCPA-2-ethylhexyl) (Dow AgroSciences); 'PrePass' (+ glyphosate-isopropylammonium) (Dow AgroSciences); 'Spectrum' (+ MCPA-2-ethylhexyl+ clopyralid) (Dow AgroSciences)
OTHER PRODUCTS
'Broadsmash' (Dow AgroSciences); 'EF-1343' (Dow AgroSciences)
MAMMALIAN TOXICOLOGY
Oral Acute oral LD50 for rats >6000 mg/kg. Skin and eye Acute percutaneous LD50 for rabbits >2000 mg/kg. Not classified for skin or eye irritation. NOEL (90 d) for rats and mice 100 mg/kg b.w. daily Other Negative in genotoxicity and Ames tests.
ECOTOXICOLOGY
Birds Acute oral LD50 for quail 1046 mg/kg. Dietary LC50 for quail and mallard ducks >5000 mg/kg diet. Fish LC50 (96 h) for bluegill sunfish >98, rainbow trout >96 mg/l. Daphnia LC50 (48 h) >292 mg/l. Algae EC50 (72 h) for algae 8.94 mg/l. Bees LD50 (48 h, oral and contact) >100 mg/bee. Worms LC50 (14 d) for earthworms >1320 mg/kg.
ENVIRONMENTAL FATE
Soil/Environment In laboratory soil studies, aerobic, microbial degradation is rapid, proceeding initially by demethylation to the 5-hydroxy material, DT50 <5 d, DT90 <16 d; this is then degraded by opening of the pyrimidine ring, DT50 7-31 d, DT90 33-102 d, followed by conversion to triazole-3-sulfonamide and ultimately formation of CO2 and soil-bound residues (R. Jackson & D. Ghosh, Proc. 9th IUPAC Int. Congr. Pestic. Chem., London, 1998, 2, 6A-014). In field studies, DT50 2-18 d. None of the degradates has activity on ALS tests, or against indicator species. Anaerobic aquatic DT50 13 d; aerobic aquatic DT50 3 d. Kd 0.13 ml/g (UK sandy clay loam), 0.33 ml/g (US loamy sand). Lysimeter studies indicate that neither florasulam nor its degradates should leach into groundwater at levels exceeding the EU trigger value. See A. R. Thompson et al., Proc. Br. Crop Prot. Conf. - Weeds, 1999, 1, 73.
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