Herbicide

NOMENCLATURE

Common name clodinafop-propargyl

IUPAC name prop-2-ynyl (R)-2-[4-(5-chloro-3-fluoropyridin-2-yloxy)phenoxy]propionate 

Chemical Abstracts name propynyl (R)-2-[4-[(5-chloro-3-fluoro-2-pyridinyl)oxy]phenoxy]propanoate 

CAS RN [105512-06-9]; [105511-96-4] racemate Development codes CGA 184927 (Ciba-Geigy) 

PHYSICAL CHEMISTRY

Composition (R)- isomer. Mol. wt. 349.7 M.f. C₁₇H₁₃ClFNO₄ Form Colourless crystals. M.p. 59.5 ºC; (tech., 48.2-57.1 ºC) V.p. 3.19 ´ 10^-3 mPa (25 ºC) (OECD 104) K_OW logP = 3.9 (25 ºC) Henry 2.79 ´ 10^-4 Pa m³ mol^-1 (calc.) S.g./density 1.37 (20 °C) Solubility In water 4.0 mg/l (pH7, 25 ºC). In ethanol 97, acetone 880, toluene 690, n-hexane 0.0086, n-octanol 25 (all in g/l, 25 ºC).  Stability Relatively stable in acidic media at 50 ºC, hydrolyses in alkaline media; DT₅₀ (25 ºC) 64 h (pH 7), 2.2 h (pH 9). 

APPLICATIONS

Biochemistry Fatty acid synthesis inhibitor, by inhibition of acetyl CoA carboxylase (ACCase). Mode of action Post-emergence, systemic grass herbicide. Phytotoxic symptoms appear within 1-3 weeks, affecting meristematic tissue. Uses Used for post-emergence control of annual grasses, including Avena, Lolium, Setaria, Phalaris and Alopecurus, in cereals, at 30-60 g/ha. Phytotoxicity Low toxicity to spring and winter wheat. Formulation types EC; WP. Compatibility Mainly used in combination with the safener cloquintocet-mexyl. Selected tradenames: mixtures: 'Celio' (+ cloquintocet-mexyl) (France) (Syngenta); 'Topik' (+ cloquintocet-mexyl) (Syngenta)

MAMMALIAN TOXICOLOGY

Oral Acute oral LD₅₀ for male rats 1392, female rats 2271, mice >2000 mg/kg. Skin and eye Acute percutaneous LD₅₀ for rats >2000 mg/kg. Non-irritating to eyes and skin (rabbits). May cause skin sensitisation (guinea pigs). Inhalation LC₅₀ (4 h) for rats 2.325 mg/l air. NOEL (2 y) for rats 0.35, (18 mo) for mice 1.2, (1 y) for dogs 3.3 mg/kg b.w. daily. ADI 0.004 mg/kg b.w. Toxicity class WHO (a.i.) III EC hazard (R22, R43) 

ECOTOXICOLOGY

Birds LD₅₀ (8 d) for mallard ducks >2000, bobwhite quail >1455 mg/kg. Fish LC₅₀ (96 h) for rainbow trout 0.39, carp 0.46, catfish 0.43 mg/l. Daphnia LC₅₀ (48 h) >74 mg/l. Algae EC₅₀ (96-120 h) for Scenedesmus subspicatus 25, Microcystis >65.5, Navicula 6.8 mg/l. Bees LD₅₀ (48 h, oral and contact) >100 mg/bee. Worms LC₅₀ for earthworms 210 mg/kg. 

ENVIRONMENTAL FATE

Animals Hydrolysed to the corresponding acid which is excreted in urine and faeces. Plants In plants, rapidly degraded to the acid derivative as major metabolite. Soil/Environment In soil, undergoes rapid degradation to the free acid (DT₅₀ <2 h) and then further to phenyl and pyridine moieties which are bound to the soil and mineralised. The free acid is mobile in soil, but is further degraded with DT₅₀ 5-20 d; in practice, there is a negligible leaching potential.