Chemical Abstracts name ethyl ( R)-2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoate CAS RN [71283–80–2] Development codes Hoe 046360 (Hoechst); AE F046360 (AgrEvo) Smiles code CCOC(=O)[C@@H](C)Oc1ccc(Oc2nc3ccc(Cl)cc3o2)cc1;without stereochemistry:CCOC(=O)C(C)Oc1ccc(Oc2nc3ccc(Cl)cc3o2)cc1
fenoxaprop-P
Common name fenoxaprop-P (BSI, E-ISO); fénoxaprop-P (( m) F-ISO)
IUPAC name ( R)-2-[4-(6-chloro-1,3-benzoxazol-2-yloxy)phenoxy]propionic acid; ( R)-2-[4-(6-chlorobenzoxazol-2-yloxy)phenoxy]propionic acid
Chemical Abstracts name ( R)-2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid CAS RN [113158–40–0] Development codes Hoe 088406 (Hoechst); AE F088406 (AgrEvo)
PHYSICAL CHEMISTRY
fenoxaprop-P-ethyl
Mol. wt. 361.8 M.f. CHClNO Form White, odourless solid. M.p. 89–91 °C V.p. 5.3 × 10 mPa (20 °C) K logP = 4.58 Henry 2.74 × 10 Pa m mol (calc.) S.g./density 1.3 (20 °C) Solubility In water 0.7 mg/l (pH 5.8, 20 °C). In acetone, toluene and ethyl acetate >200, methanol 43 (all in g/l, 20 °C). Stability Fenoxaprop-P-ethyl is stable for 90 d at 50 °C. Not sensitive to light. Hydrolysis DT 2.8 d (pH 4), 19.2 d (pH 5), 23.2 d (pH 7), 0.6 d (pH 9) (25 °C) ( EFSA Sci. Rep. (2007) 121, 1–76).
fenoxaprop-P
Mol. wt. 333.7 M.f. CHClNO Form Light beige, weakly pungent, fine powder. M.p. 155–161 °C V.p. 3.5 × 10 mPa K logP = 1.83–0.24 (pH 5–9) Henry 1.91 × 10 Pa m mol(pH 7.0, calc.) S.g./density c. 1.5 (20 °C) Solubility In water 0.27 (pH 5.1), 61 (pH 7.0) (both in g/l, 20 °C). In acetone 80, toluene 0.5, ethyl acetate 36, methanol 34 (all in g/l, 20 °C).
COMMERCIALISATION
History The herbicidal enantiomer of fenoxaprop was reported by H. P. Huff et al. ( Proc. Br. Crop Prot. Conf. - Weeds, 1989, 2, 717). Introduced by Hoechst AG (now Bayer AG) in 1988.
Biochemistry Fatty acid synthesis inhibition in grasses, by inhibition of acetyl CoA carboxylase (ACCase). Rapidly hydrolysed in plants to the acid, which is still herbicidally active. Mode of action Fenoxaprop-P-ethyl is a selective herbicide with contact and systemic action, absorbed principally by the leaves, with translocation both acropetally and basipetally to the roots or rhizomes.
Uses Post-emergence control of annual and perennial grass weeds in potatoes, beans, soya beans, beets, vegetables, peanuts, flax, oilseed rape and cotton; and (when applied with the herbicide safener mefenpyr-diethyl) annual and perennial grass weeds and wild oats in wheat, rye, triticale and, depending on ratio, in some varieties of barley. Applied at 40–90 g/ha in cereals (max. 83 g/ha in EU) and at 30–140 g/ha in broad-leaved crops. Phytotoxicity Non-phytotoxic to broad-leaved crops.
Product analysis by hplc with uv detection; enantiomeric purity by chiral phase separation, followed by uv detection ( CIPAC Handbook, 2000, J, 51). Details are also available from Bayer CropScience.
TOXICOLOGICAL & ENVIRONMENTAL REVIEWS
EFSA Sci. Rep. (2007) 121, 1–76. 91/414/EC Annex I status Included, 2008/66/EC.
MAMMALIAN TOXICOLOGY
fenoxaprop-P-ethyl
Oral Acute oral LD for rats 3150–4000, mice >5000 mg/kg. Skin and eye Acute percutaneous LD for rats >2000 mg/kg. Inhalation LC (4 h) for rats >1.224 mg/l air. NOEL (90 d) for rats 0.75 mg/kg b.w. daily (10 ppm), for mice 1.4 mg/kg b.w. daily (10 ppm), for dogs 15.9 mg/kg b.w. daily (400 ppm). ADI/RfD (EC) 0.01 mg/kg b.w. [2008].
Plants In plants, fenoxaprop-P-ethyl is metabolised via fenoxaprop-P to 6-chloro-2,3-dihydrobenzoxazol-2-one. Soil/Environment In soil, fenoxaprop-P-ethyl is rapidly hydrolysed to fenoxaprop-P (A. E. Smith, J. Agric. Food Chem., 1985, 33, 483); DT 1–10 d.
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