Herbicide

HRAC  K3 WSSA  15; chloroacetamide

NOMENCLATURE

Common name alachlor (BSI, E-ISO, ANSI, WSSA, JMAF); alachlore ((m) F-ISO)

IUPAC name 2-chloro-2',6'-diethyl-N-methoxymethylacetanilide 

Chemical Abstracts name 2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide 

CAS RN [15972-60-8]  EEC no. 240-110-8  Development codes CP 50144 (Monsanto); MON 0144 (tech.) (Monsanto) 

PHYSICAL CHEMISTRY

Composition ³93% pure.  Mol. wt. 269.8  M.f. C14H20ClNO2  Form Yellow white to wine red, odourless solid (room temperature); yellow to red liquid (>40 °C).  M.p. 40.5-41.5 ºC  B.p. 100 °C/0.0026 kPa  V.p. 2.0 mPa (25 ºC)  KOW logP = 3.09  Henry 3.2 ´ 10-3 Pa m3 mol-1 (calc.)  S.g./density 1.1330 (25 °C)  Solubility In water 170.31 mg/l (pH 7, 20 ºC). Soluble in diethyl ether, acetone, benzene, chloroform, ethanol, and ethyl acetate. Slightly soluble in heptane.  Stability Hydrolysed by strong acids and alkalis. Stable to u.v. light. Decomposes at 105 ºC.  F.p. 137 °C (closed cup); 160 °C (open cup) 

COMMERCIALISATION

History Herbicide reported by R. F. Husted et al. (Proc. North Cent. Weed Control Conf., 1966, 21, 44). Introduced by Monsanto Co.  Patents US 3442945; US 3547620  Manufacturers Comlets; Crystal; ÉMV; Krishi Rasayan; Makhteshim-Agan; Monsanto; Pilarquim; Rallis; RPG; Sanachem; Sinon; Sundat

APPLICATIONS

Biochemistry Acts by inhibition of protein synthesis and root elongation. Maize tolerance is attributed to rapid detoxification by glutathione transferases.  Mode of action Selective systemic herbicide, absorbed principally by germinating shoots, but also by the roots, with translocation throughout the plant, and accumulation mainly in vegetative parts rather than in reproductive parts.  Uses Used pre-emergence at 1.68-4.48 kg/ha to control annual grasses and many broad-leaved weeds in cotton, brassicas, maize, oilseed rape, peanuts, radish, soya beans and sugar cane.  Formulation types EC; GR; ME; WG.  Selected tradenames: 'Lasso' (Monsanto); 'Alanex' (Makhteshim-Agan); 'Cattch' (RPG); 'Lacorn' (Efthymiadis); 'Satochlor' (ÉMV); 'Sholay' (Rallis); 'Top 48' (Cequisa); mixtures: 'Cotralin' (+ prometryn) (Efthymiadis)

OTHER TRADENAMES

'Cropstar II' (Monsanto); 'Micro-Tech' (Monsanto); 'Partner' (Monsanto); 'Alac' (Chemia); 'Alagan' (Makhteshim-Agan); 'Alanox' (Crystal); 'Chemiclor' (Chemiplant); 'Dipachlor' (Papaeconomou); 'Pilarzo' (Pilarquim) mixtures: 'Bronco' (+ glyphosate) (isopropylammonium salt) (Monsanto); 'Bullet' (+ atrazine) (Monsanto); 'Freedom' (+ trifluralin) (Monsanto); 'Lariat' (+ atrazine) (Monsanto); 'Alazine' (+ atrazine) (Makhteshim-Agan); 'Manager' (+ aclonifen) (Aventis); 'Propachlor Doble' (+ atrazine) (Probelte); 'Top Hand' (+ furilazole+ halosulfuron-methyl) (Nissan)

ANALYSIS

Product analysis by glc with FID (J. M. Warner & D. D. Arras in Comp. Anal. Profiles, Chapt. 5; AOAC Methods, 1995, 985.04, 988.03; CIPAC Handbook, 1985, 1C, 4; ibid., 1992, E, 4). Residues in water and in soil determined by glc with ECD or FID; details, and other methods reviewed by J. M. Warner & D. D. Arras, loc. cit.; see also AOAC Methods, 1995, 991.07. Details also available from Monsanto Co. 

MAMMALIAN TOXICOLOGY

Oral Acute oral LD50 for rats 930-1350 mg/kg.  Skin and eye Acute percutaneous LD50 for rabbits 13 300 mg/kg. Non-irritating to skin or eyes (rabbits). Contact sensitisation reactions observed in guinea pigs.  Inhalation LC50 (4 h) for rats 1.04 mg/l air.  NOEL (2 y) for rats £2.5 mg/kg b.w. daily; (1 y) for dogs £1 mg/kg b.w. daily. In 90 d feeding trials, rats and dogs receiving 200 mg/kg diet showed no ill-effects.  Water GV 20 mg/l (based on incidence of cancer in animals).  Other Oncogenic in rats but not in mice.  Toxicity class WHO (a.i.) Ia; EPA (formulation) III  EC hazard R40| Xn; R22| R43 

ECOTOXICOLOGY

Birds Acute oral LD50 for bobwhite quail 1536 mg/kg. LC50 (5 d) for mallard ducks and bobwhite quail >5620 mg/kg diet.  Fish LC50 (96 h) for rainbow trout 1.8, bluegill sunfish 2.8, fathead minnow 5.0, channel catfish 2.1 mg/l.  Daphnia EC50 (48 h) 10 mg/l.  Algae TL50 (72 h) for Selenastrum capricornutum 12 mg/l.  Other aquatic spp. EC50 (48 h) for crayfish >320 mg/l.  Bees Not hazardous to bees when used as directed; LD50 32 mg/bee.  Worms LC50 (14 d) for earthworms 387 mg/kg dry soil. 

ENVIRONMENTAL FATE