Insecticide Esfenvalerate

NOMENCLATURE Esfenvalerate

Common name esfenvalerate (BSI, E-ISO, (m) F-ISO)

IUPAC name (S)-a-cyano-3-phenoxybenzyl (S)-2-(4-chlorophenyl)-3-methylbutyrate 

Chemical Abstracts name [S-(R*,R*)]-cyano(3-phenoxyphenyl)methyl 4-chloro-2-(1-methylethyl)benzeneacetate 

Other names fenvalerate-U CAS RN [66230-04-4] Development codes S-1844; S-5602 Aa (both to Sumitomo); DPX-YB656 (Du Pont) Official codes OMS 3023 

PHYSICAL CHEMISTRY Esfenvalerate

Composition Tech. is ³98% total isomers and ³75% resolved (S,S)- isomers. Mol. wt. 419.9 M.f. C₂₅H₂₂ClNO₃ Form Colourless crystals; (tech., yellow-brown viscous liquid or solid at 23 ºC). M.p. 59.0-60.2 ºC; (tech., 43.3-54 °C) B.p. 151-167 ºC (tech.) V.p. 2 ´ 10^-4 mPa (25 ºC) K_OW logP = 6.22 (25 ºC) Henry 4.20 ´ 10^-2 Pa m³ mol^-1 (calc.) S.g./density 1.26 (4-26 ºC) Solubility In water 0.002 mg/l (25 ºC). In xylene, acetone, chloroform, ethyl acetate, dimethylformamide, dimethyl sulfoxide >600, hexane 10-50, methanol 70-100 (all in g/kg, 25 ºC). Stability Relatively stable to heat and light. Stable to hydrolysis at pH 5, 7 and 9 (25 °C). Specific rotation [a]_D²⁵ -15.0?(c 2.0 in methanol) F.p. 256 °C (Pensky-Martens) 

MAMMALIAN TOXICOLOGY Esfenvalerate

Oral Acute oral LD₅₀ for rats 75-88 mg/kg. Skin and eye Acute percutaneous LD₅₀ for rats >5000, rabbits >2000 mg/kg. Slight skin irritant; mild eye irritant. Not a skin sensitiser. NOEL No effect on sub-chronic studies at ³2 mg/kg daily. ADI 0.02 mg/kg. Other Acute LD₅₀ values vary with the vehicle, concentration, route and species, etc.; values reported sometimes differ markedly. No carcinogenic, developmental or reproductive toxicity in animal tests. Toxicity class WHO (a.i.) II; EPA (formulation) II EC hazard T; R23/25| R43| N; R50, R53 

ECOTOXICOLOGY Esfenvalerate

Birds Acute oral LD₅₀ for bobwhite quail 381 mg/kg. LC₅₀ (8 d) for bobwhite quail >5620, mallard ducks 5247 ppm. Fish Extremely toxic to aquatic animals. LC₅₀ (96 h) for fathead minnows 0.690, bluegill sunfish 0.26, rainbow trout 0.26 mg/l. Daphnia LC₅₀ (48 h) 0.24 mg/l. Bees LD₅₀ (contact) 0.017 mg/bee. 

ENVIRONMENTAL FATE Esfenvalerate

Animals Rapid metabolism and elimination occurs in rats and other animals. Primary metabolism involves hydroxylation of 2'- and 4'- hydroxyl moieties, ester cleavage, hydroxylation and oxidation of the alcohol derivatives, oxidation of the cyano moiety and conjugation of the acidic metabolites with sulfate, glycine and glucuronic acid. Plants The major metabolite was decarboxylated fenvalerate. Ester cleavage, hydration of the cyano group to carboxamide and carboxylic acid, hydroxylation of the 2'- and 4'- phenoxy positions, conversion of the alcohol moiety to 3-phenoxybenzyl alcohol and 3-phenoxybenzoic acid, and conjugation of the resulting carboxylic acids and alcohols with sugars, also occur. Soil/Environment In sand (0.38% o.m.), K_d (25 ºC) 4.4; in sandy loam (pH 7.3, 1.1% o.m.), K_d (25 ºC) 6.4, DT₅₀ 88 d; in silty loam (pH 5.3, 2.0% o.m.), K_d (25 ºC) 71, DT₅₀ 114 d; in clay loam (pH 5.7, 0.2% o.m.), DT₅₀ 287 d; in clay loam (pH 6.4, 1.5% o.m.), K_d (25 ºC) 105. K_oc 5300.