Herbicide

HRAC  K3 WSSA  15; chloroacetamide

NOMENCLATURE

Common name pretilachlor (BSI, E-ISO); prétilachlore ((m) F-ISO)

IUPAC name 2-chloro-2',6'-diethyl-N-(2-propoxyethyl)acetanilide 

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

CAS RN [51218-49-6]  Development codes CGA 26 423 (Ciba-Geigy) 

PHYSICAL CHEMISTRY

Mol. wt. 311.9  M.f. C17H26ClNO2  Form Colourless liquid.  B.p. 135 ºC/0.001 mmHg  V.p. 0.133 mPa (20 ºC)  KOW logP = 4.08 (shake flask)  Henry 8.1 ´ 10-4 Pa m3 mol-1  S.g./density 1.076 (20 ºC)  Solubility In water 50 mg/l (20 ºC). Very soluble in benzene, hexane, methanol and dichloromethane.  Stability Relatively stable to hydrolysis; DT50 (calc.) (20 ºC) >200 d (pH 1-9), 14 d (pH 13).  F.p. 129 °C (EEC A9) 

COMMERCIALISATION

History Introduced by Ciba-Geigy AG (now Syngenta AG) in 1988.  Patents BE 800471; GB 1438311; GB 1438312  Manufacturers Syngenta

APPLICATIONS

Biochemistry Cell division inhibitor.  Mode of action Selective herbicide. It is taken up readily by the hypocotyls, mesocotyls and coleoptiles, and, to a lesser extent, by the roots of germinating weeds.  Uses Herbicide effective against main annual grasses, broad-leaved weeds and sedges in transplanted and seeded rice, at 1-1.25 kg/ha.  Phytotoxicity Applied alone, pretilachlor will cause injury to direct-seeded rice.  Formulation types EC; GR.  Selected tradenames: 'Rifit' (transplanted rice) (Syngenta); 'Solnet' (transplanted rice) (Syngenta); 'Gorbo' (Takeda); mixtures: 'Sofit' (+ fenclorim) (direct-sown rice) (Syngenta); 'Sparkstar G' (+ dimethametryn+ esprocarb+ pyrazosulfuron-ethyl) (Nissan, Syngenta)

OTHER TRADENAMES

Mixtures: 'Kusa Kont' (+ benzobicyclon) (SDS Biotech KK, Syngenta, Sankyo); 'Hayate' (+ daimuron+ dimethametryn+ imazosulfuron) (Takeda); 'Kusahope D' (+ dimethametryn+ pyrazolynate) (Sankyo); 'Pulgman' (+ daimuron+ ethoxysulfuron) (Aventis); 'Sheriff' (+ cyhalofop-butyl+ dimethametryn+ imazosulfuron) (Otsuka, Takeda); 'Sing' (+ pyributicarb) (Sankyo); 'Slasher' (+ bromobutide+ dimethametryn+ pyrazolynate) (Sankyo); 'Tabijin A' (+ azimsulfuron+ bensulfuron-methyl+ cyhalofop-butyl+ pyriminobac-methyl) (Kumiai); 'Topran' (+ ethoxysulfuron+ pyrazolynate) (Aventis); 'Urifos' (+ benfuresate+ dimethametryn+ pyrazolynate) (Sankyo) Discontinued names: 'Erijan' * (Ciba); 'Kusahope' * (Sankyo)

ANALYSIS

Product analysis by glc. Residues determined by glc with MCD or TID. Details available from Syngenta. 

MAMMALIAN TOXICOLOGY

Oral Acute oral LD50 for rats 6099 mg/kg.  Skin and eye Acute percutaneous LD50 for rats >3100 mg/kg. Moderate irritant to skin; non-irritant to eyes (rabbits).  Inhalation LC50 (4 h) for rats >2.8 mg/l air.  NOEL (2 y) for rats 30, mice 300 ppm; (0.5 y) for dogs 300 ppm.  ADI 0.018 mg/kg.  Toxicity class WHO (a.i.) III (Table 5)  EC hazard (R38, R43) 

ECOTOXICOLOGY

Birds Non-toxic to birds; LD50 for Japanese quail >10 000 mg/kg. LC50 for Japanese quail >1000 ppm.  Fish LC50 (96 h) for rainbow trout 0.9, catfish 2.7, crucian carp 2.3 mg/l.  Daphnia LC50 13 mg/l.  Algae EC50 for Selenastrum capricornutum 0.002 mg/l.  Bees LD50 (contact) 93 mg/bee. 

ENVIRONMENTAL FATE