Herbicide
HRAC  B WSSA  2; sulfonylurea



NOMENCLATURE
chlorimuron-ethyl
Common name chlorimuron-ethyl
IUPAC name ethyl 2-(4-chloro-6-methoxypyrimidin-2-ylcarbamoylsulfamoyl)benzoate 
Chemical Abstracts name ethyl 2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoate 
CAS RN [90982-32-4]  Development codes DPX-F6025 (Du Pont) 

chlorimuron
Common name chlorimuron (BSI, ANSI, WSSA, draft E-ISO, draft F-ISO)
IUPAC name 2-(4-chloro-6-methoxypyrimidin-2-ylcarbamoylsulfamoyl)benzoic acid 
Chemical Abstracts name 2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoic acid 
CAS RN [99283-00-8] 

PHYSICAL CHEMISTRY
chlorimuron-ethyl
Composition Tech. is >95%.  Mol. wt. 414.8  M.f. C₁₅H₁₅ClN₄O₆S  Form Colourless crystals.  M.p. 181 ºC  V.p. 4.9 × 10^-7 mPa  K_OW logP = 0.11 (pH 7)  Henry 1.7 × 10^-10 Pa m³ mol^-1  S.g./density 1.51 (25 ºC)  Solubility In water 9 (pH 5), 1200 (pH 7) (both in mg/l, 25 ºC). Low solubility in organic solvents.  Stability In water DT₅₀ 17-25 d (pH 5, 25 ºC).  pKa 4.2 

chlorimuron
Mol. wt. 386.8  M.f. C₁₃H₁₁ClN₄O₆S

APPLICATIONS
chlorimuron-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. Crop selectivity derives from plant metabolism both by homoglutathione conjugation and by de-esterification (M. K. Koeppe & H. M. Brown, Agro-Food-Industry, 6, 9-14 (1995)).  Uses Used post-emergence for control of important broad-leaved weeds, such as cocklebur, pigweed, sunflower and annual morning glory, in soya beans and peanuts. Active at 9-13 g/ha.  Formulation types WG.

ANALYSIS
Product analysis by hplc (R. A. Guinivan et al., Anal. Methods Pestic. Plant Growth Regul., 1988, 16, 37). Residues determined by hplc (J. L. Prince & R. A. Guinivan, J. Agric. Food Chem., 1988, 36, 1). Methods for sulfonylurea residues in crops, soil and water reviewed (A. C. Barefoot et al., Proc. Br. Crop Prot. Conf. - Weeds, 1995, 2, 707). 

MAMMALIAN TOXICOLOGY
Oral Acute oral LD₅₀ for rats 4102 mg/kg.  Skin and eye Acute percutaneous LD₅₀ for rabbits >2000 mg/kg. Not a skin irritant or eye irritant (rabbits). Not a skin sensitiser (guinea pigs).  Inhalation LC₅₀ (4 h) for rats >5 mg/l air.  NOEL (2 y) for rats 250 mg/kg diet (12.5 mg/kg daily); (1 y) for dogs 250 mg/kg diet (6.25 mg/kg daily). NOEL in: reproduction (2-generation) in rats 250 mg/kg diet; teratogenicity in rats 30, rabbits 15 mg/kg.  ADI 0.020 mg/kg b.w.  Toxicity class WHO (a.i.) III (Table 5); EPA (formulation) III

ECOTOXICOLOGY
chlorimuron-ethyl
Birds Acute oral LD₅₀ (14 d) for mallard ducks >2510 mg/kg. Dietary LC₅₀ for mallard ducks and bobwhite quail >5620 ppm.  Fish LC₅₀ (96 h) for trout >1000, bluegill sunfish >100 mg/l.  Daphnia LC₅₀ (48 h) 1000 mg/l.  Other aquatic spp. For Lemna gibba, EbC₅₀ 0.45 ppb, ErC₅₀ 45 mg/l, EC₅₀ (frond counts) 0.27 ppb. LC₅₀ for crayfish >1000 ppm.  Bees LD₅₀ (48 h) >12.5 mg/bee.  Worms LC₅₀ for earthworms (Eisenia foetida) >4050 mg/kg.

ENVIRONMENTAL FATE
chlorimuron-ethyl
Animals Chlorimuron-ethyl is rapidly and extensively metabolised in the hen; 18 metabolites in the excreta were resolved by hplc.  Soil/Environment In soil, K_d >1.60 (pH 4.5, 5.6% o.m.), 0.28 (pH 5.8, 4.3 % o.m.), <0.03 (pH 6.5, 2.1% o.m.), <0.03 (pH 6.6, 1.1 % o.m.).