Dimethoate

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Chemical Identification | General Product Information | Physical & Safety Data

Chemical Identification

Common Name

Dimethoate

中文通用名

乐果

IUPAC

O,O-dimethyl S-methylcarbamoylmethyl phosphorodithioate
or
2-dimethoxyphosphinothioylthio-N-methylacetamide

CAS

O,O-dimethyl S-[2-(methylamino)-2-oxoethyl] phosphorodithioate

CAS No.

60-51-5

Molecular Formula

C₅H₁₂NO₃PS₂

Molecular Structure

General Product Information

Category

Insecticides > Organophosphorus insecticides

Activity

Acaricide/Miticide, insecticide

Premix

Lambda-cyhalothrin+dimethoate
Imidacloprid+dimethoate
Fenvalerate+dimethoate
Fenpropathrin+dimethoate
Endosulfan+dimethoate
Deltamethrin+dimethoate
Cypermethrin+dimethoate
Aerosol spray, dust, emulsifiable concentrate, ULV concentrate. Premix Parters: iprodione.

Physical & Safety Data

Physical Properties

Molecular weight:229.3. Physical form:Colourless crystals, mercaptan odor,( tech., white to greyish crystals). Density:1.277 at 65 °C; Composition:Tech. grade is 95% pure. Melting point:49 °C; ( tech., 43-45 °C); Vapour pressure:0.25 mPa (25 °C); Henry constant:1.2×10-6 Pa m3 mol-1; Partition coefficient(n-octanol and water):logP = 0.704; Solubility:In water 23.3 ( pH 5), 23.8 ( pH 7), 25.0 ( pH 9) (all in g/l, 20 °C). Readily soluble in most organic solvents, e.g. in alcohols, ketones, benzene, toluene, chloroform, dichloromethane >300, carbon tetrachl. Stability: Relatively stable in aqueous media at pH 2-7. Hydrolysed in alkaline solutions; DT50 12 d ( pH 9). Decomposes on heating, forming the O,S-dimethyl analogue. Highly soluble in chloroform, methylene chloride, benzene, toluene, alcohols, esters, ketones. Slightly in xylene, carbon tetrachloride, aliphatic hydrocarbons.

Toxicology

Oral:Acute oral LD₅₀ for rats 387 mg/kg, mice 160 mg/kg, rabbits 300 mg/kg, guinea pigs 350 mg/kg. Percutaneous:Acute percutaneous LD₅₀ for rats >2000 mg/kg. Non-irritating to skin (rabbits). Inhalation: LC₅₀ (4 h) for rats >1.6 mg/l air. Phytotoxicity:Non-phytotoxic when used as directed, except to some varieties of lemon, peach, fig, olive, walnut, hop, tomato, bean, cotto

Environmental Profile

Ecotoxicology:
Algae: EC₅₀ (72 h) for Selenastrum capricornutum 282.3 mg/l; NOEC (72 h) 30.5 mg/l.Bees:Toxic to bees. LD₅₀ (oral and topical) 0.1-0.2 µg/bee.Birds:Acute oral LD₅₀ for male pheasants 15, quail 84, chickens 108, female mallard ducks 40 mg/kg.Daphnia: LC₅₀ (24 h) 4.7 mg/l; NOEC (24 h) 1 mg/l.Fish: LC₅₀ (96 h) for mosquito fish 40-60, rainbow trout 6.2, bluegill sunfish 6 mg/l.
Environmental fate:
Dimethoate degrades with short half-life in soil, water and plants. When used correctly, exposure of the population through air, food or water is negligible.Animals:In mammals, metabolism follows the same pattern as in plants.Soil:Adsorption and desorption constants have been shown to be a linear function of soil silt content. K_oc ranges from 16.25 (sandy loam) to 51.88 (sand/loamy sand). Aerobic DT₅₀ 2-4.1 d. Plant:In plants, oxidised to O,O-dimethyl-phosphorothioate and hydrolysed to O,O-dimethyl-phosphorodithioate, -phosphorothioate, and -phosphate. The ester group is demethylated and the methylamino group is hydrolytically cleaved.
WATER SOLUBILITY: 2.5% at 21°C.

Transport Information

Signal Word:WARNING; Hazard Class:II (Moderately hazardous)