|
tribenuron-methyl
Herbicide
HRAC B WSSA 2; sulfonylurea
NOMENCLATURE
tribenuron-methyl
Common name tribenuron-methyl
IUPAC name methyl 2-[4-methoxy-6-methyl-1,3,5-triazin-2-yl(methyl)carbamoylsulfamoyl]benzoate
Chemical Abstracts name methyl 2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)methylamino]carbonyl]amino]sulfonyl]benzoate
CAS RN [101200-48-0] EEC no. 401-190-1 Development codes DPX-L5300 (DuPont); L5300
tribenuron
Common name tribenuron (BSI, ANSI, draft E-ISO)
IUPAC name 2-[4-methoxy-6-methyl-1,3,5-triazin-2-yl(methyl)carbamoylsulfamoyl]benzoic acid
Chemical Abstracts name 2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)methylamino]carbonyl]amino]sulfonyl]benzoic acid
CAS RN [106040-48-6]
PHYSICAL CHEMISTRY
tribenuron-methyl
Composition Tech. is >95%. Mol. wt. 395.4 M.f. C15H17N5O6S Form Off-white powder with a slight pungent odour. M.p. 142 ºC V.p. 5.2 ´ 10-5 mPa (25 ºC) KOW logP = 0.78 (pH 7, 25 °C) Henry 1.03 ´ 10-8 Pa m3 mol-1 S.g./density 1.46 (20 °C) Solubility In water 0.05 (pH 5), 2.04 (pH 7), 18.3 (pH 9) (g/l, 20 ºC). In acetone 3.91 ´ 104, acetonitrile 4.64 ´ 104, ethyl acetate 1.63 ´ 104, n-heptane 20.8, methanol 2.59 ´ 103 (mg/l, 20 °C). Stability No significant photolysis occurs over the pH range 5-9 at 25 ºC. Does not ignite nor support combustion. Hydrolysis DT50 <1 d (pH 5), 15.8 d (pH 7), stable (pH 9) (all 25 ºC). pKa 4.7
tribenuron
Mol. wt. 381.4 M.f. C14H15N5O6S
COMMERCIALISATION
History Herbicide reported by D. T. Ferguson et al. (Proc. Br. Crop Prot. Conf. - Weeds, 1985, 1, 43). The methyl ester introduced in Spain (1986) by E. I. du Pont de Nemours and Co. ; first approval in 1987. Manufacturers DuPont; Jiangsu Yangnong; Sharda; Shenyang
APPLICATIONS
tribenuron-methyl
Biochemistry Affects sensitive weeds through inhibition of the enzyme acetolactate synthase (ALS). Inhibition of ALS leads to the rapid cessation of cell division and subsequent growth processes in plants. Mode of action Selective, post-emergence herbicide, acting primarily through foliar uptake, with little or no soil activity. Symptoms of chlorosis appear in affected weeds in days with necrosis and death occuring after 10-25 days under optimal conditions. Uses Post-emergence control of broad-leaved weeds in cereal crops, including wheat, barley, oats, rye and triticale, at 7.5-30 g/ha. Formulation types TB; WG. Selected products: 'Express' (USA) (DuPont); 'Granstar' (Europe) (DuPont); 'Pointer' (Germany) (DuPont); 'Oscar' (Vapco); 'Rapid' (Rotam); mixtures: 'Canvas' (+ metsulfuron-methyl+ thifensulfuron-methyl) (DuPont)
OTHER PRODUCTS
tribenuron-methyl
'Cameo' (DuPont); 'Quantum' (DuPont); 'Sprinter' (DuPont) mixtures: 'Calibre' (+ thifensulfuron-methyl) (DuPont); 'Harmony Extra' (+ thifensulfuron-methyl) (DuPont) Discontinued products mixtures: 'DP 911' * (+ metsulfuron-methyl) (DuPont); 'DUK 110' * (+ thifensulfuron-methyl) (DuPont)
ANALYSIS
Product and residue analysis by hplc/ms/ms (Handbook of Residue Analytical Methods, pp 400-410).
MAMMALIAN TOXICOLOGY
tribenuron-methyl
Oral Acute oral LD50 for rats >5000 mg/kg. Skin and eye Acute percutaneous LD50 for rabbits >5000 mg/kg. Non-irritating to skin and eyes (rabbits). Mildly sensitising to skin (guinea pig maximisation test), but not likely to be a dermal sensitisation risk to humans. Inhalation LC50 (4 h) for rats >5.0 mg/l air. NOEL (2 y) for rats 25 ppm diet; (18 mo) for mice 200 ppm diet (25 mg/kg b.w. daily); (1 y) for dogs 250 ppm diet (8.2 mg/kg b.w. daily); (90 d) for rats 100, for mice 500, for dogs 500 mg/kg diet. ADI 0.01 mg/kg Other Not genotoxic. Toxicity class WHO (a.i.) U; EPA (formulation) III EC classification R43
ECOTOXICOLOGY
tribenuron-methyl
Birds Acute oral LD50 for bobwhite quail >2250 mg/kg. Dietary LC50 (8 d) for bobwhite quail and mallard ducks >5620 mg/kg. Fish LC50 (96 h) for rainbow trout 738 mg/l. Daphnia LC50 (48 h) 894 mg/l. Algae EC50 (120 h) for green algae 20.8 mg/l. Other aquatic spp. EC50 (14 d) for Lemna 4.24 mg/l. Bees LD50 for honeybees (contact) >100 mg/bee; (oral) >9.1 mg/bee. Worms LC50 for earthworms >1000 mg/kg.
ENVIRONMENTAL FATE
Animals Tribenuron-methyl is rapidly and extensively metabolised in animals by N-demethylation, de-esterfication, hydrolysis of the sulfonylurea bridge, hydroxylation of the phenyl ring and/or O-demethylation of the triazine ring. Plants Tribenuron-methyl is rapidly and extensively metabolised in plants. A major metabolic reaction was N-demethylation; further metabolism is primarily through hydroxylation of the phenyl ring and conjugation with glucose. Soil/Environment DT50 of tribenuron-methyl in field soils of intended use 3.5-5.1 days. No significant photodecomposition under field conditions. Degradation in the soil occurs primarily by aqueous hydrolysis and by direct microbial degradation. Hydrolysis is affected by soil pH, being faster in acidic than alkaline soils. Losses due to volatilisation are not significant.
|