NOMENCLATURE

Common name acetochlor (BSI, E-ISO, ANSI, WSSA); acétochlore ((m) F-ISO)

IUPAC name 2-chloro-N-ethoxymethyl-6'-ethylaceto-o-toluidide 

Chemical Abstracts name 2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide 

CAS RN [34256-82-1]  EEC no. 251-899-3  Development codes MON 097 (Monsanto) 

PHYSICAL CHEMISTRY

Composition Tech. is 92% pure.  Mol. wt. 269.8  M.f. C₁₄H₂₀ClNO₂  Form Clear viscous liquid; (tech. is a wine red to yellow or amber oil).  M.p. 10.6 °C  B.p. 172 ºC/5 mmHg  V.p. 400?30 mPa (20 °C)  K_OW logP = 4.14  Henry 3.83 ´ 10^-1 Pa m³ mol^-1 (calc.)  S.g./density 1.1221 (20 °C)  Solubility In water 223 mg/l (25 ºC). Soluble in diethyl ether, acetone, benzene, chloroform, ethanol, ethyl acetate, and toluene.  Stability Stable for over 2 years at 20 ºC (EC formulation).  F.p. 160 °C (Tag closed cup) 

APPLICATIONS

Biochemistry Inhibits cell division by blocking protein synthesis. Maize tolerance of chloroacetamides is due mainly to conjugation with glutathione; P450 metabolism may also be a factor.  Mode of action Selective herbicide, absorbed mainly by the shoots and secondarily by the roots of germinating plants.  Uses Used pre-emergence or pre-plant to control annual grasses, certain annual broad-leaved weeds and yellow nutsedge in maize (at 3 kg/ha), peanuts, soya beans, cotton, potatoes and sugar cane.  Formulation types CS; EC.

ANALYSIS

Product by gc. Residues by hplc. Details from Monsanto.

MAMMALIAN TOXICOLOGY

Oral Acute oral LD₅₀ for rats 2148 mg/kg.  Skin and eye Acute percutaneous LD₅₀ for rabbits 4166 mg/kg. Contact sensitisation reactions observed in guinea pigs. Practically non-irritating to eyes and skin (rabbits).  Inhalation LC₅₀ (4 h) for rats >3.0 mg/l air.  NOEL (2 y) for rats 10 mg/kg b.w. daily; (1 y) for dogs 12 mg/kg b.w. daily.  ADI 0.01 mg/kg b.w.  Toxicity class WHO (a.i.) III  EC hazard Xn; R20| Xi; R37/38| R43| N; R50, R53 

ECOTOXICOLOGY

Birds Acute oral LD₅₀ for bobwhite quail 1260 mg/kg. LC₅₀ (5 d) for quail and mallard ducks >5620 mg/kg.  Fish LC₅₀ (96 h) for rainbow trout 0.36, bluegill sunfish 1.5 mg/l.  Daphnia LC₅₀ (48 h) 9 mg/l.  Bees LD₅₀ (24 h) (contact) >200 mg/bee; (oral) >100 mg/bee.  Worms LC₅₀ (14 d) 211 mg/kg. 

ENVIRONMENTAL FATE

Animals The primary routes of metabolism are glutathione conjugation and metabolism by cytochrome P450.  Plants In maize and soya beans, rapidly absorbed and metabolised in the germinating plant. In maize, the first metabolite is glutathione, and in soya beans homoglutathione (E. J. Breaux, J. Agric. Food Chem., 1986, 34, 884).  Soil/Environment Adsorbed by soil, with little leaching. Microbial degradation accounts for most loss from soil; DT₅₀ 8-18 d.