Methidathion

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Chemical Identification | General Product Information | Physical & Safety Data

Chemical Identification

Common Name

Methidathion

中文通用名

杀扑磷

IUPAC

S-2,3-dihydro-5-methoxy-2-oxo-1,3,4-thiadiazol-3-ylmethyl O,O-dimethyl phosphorodithioate
or
3-dimethoxyphosphinothioylthiomethyl-5-methoxy-1,3,4-thiadiazol-2(3H)-one

CAS

S-[(5-methoxy-2-oxo-1,3,4-thiadiazol-3(2H)-yl)methyl] O,O-dimethyl phosphorodithioate

CAS No.

950-37-8

Molecular Formula

C₆H₁₁N₂O₄PS₃

Molecular Structure

General Product Information

Category

Insecticides > Organophosphorus insecticides

Activity

Insecticide, acaricide

Physical & Safety Data

Physical Properties

Molecular weight:302.3; Physical form:Colourless crystals. Density:1.51 (20 °C) ( OECD 109); Melting point:39-40 °C; Vapour pressure:2.5 ×10-1 mPa (20 °C); Henry constant:3.3 × 10-4 Pa m3 mol-1 ( calc.); Partition coefficient(n-octanol and water):logP = 2.2 ( OECD 107); Solubility:In water 200 mg/l (25 °C). In ethanol 150, acetone 670, toluene 720, hexane 11, n-octanol 14 (all in g/l, 20 °C).; Stability:Rapidly hydrolysed in alkaline and strongly acidic media; DT50 (25 °C) 30 min at pH 13. Relatively stable to hydrolysis in neutral and slightly acidic media.;

Toxicology

Oral:Acute oral LD₅₀ for rats 25-54, mice 25-70, rabbits 63-80, guinea pigs 25 mg/kg. Percutaneous:Acute percutaneous LD₅₀ for rabbits 200, rats 297-1663 mg/kg. Non-irritating to eyes and skin (rabbits). Not a skin sensitiser (Buehler test). Inhalation: LC₅₀ (4 h) for rats 140 mg/m³ air.

Environmental Profile

Ecotoxicology:
Algae: EC₅₀ (72 h) for Scenedesmus subspicatus 22 mg/l.Bees:Slightly toxic to bees.Birds:Acute oral LD₅₀ for mallard ducks 23.6-28 mg/kg. LC₅₀ (8 d) for bobwhite quail 224 ppm.Fish: LC₅₀ (96 h) for rainbow trout 0.01, bluegill sunfish 0.002 mg/l.Worms: LC₅₀ (14 d) for earthworms 5.6 mg/ kg soil.Other beneficial spp.:To be rated as detrimental to most beneficial arthropods in the short term. It has a limited surface residual effect which allows a re-immigration of beneficials from untreated parts.

Environmental fate:
Animals:In mammals, methidathion is rapidly metabolised and excreted.Soil:Methidathion and its metabolites have a low mobility in soils. The compound is rapidly degraded in soil and water by chemical, photolytic and biological processes. DT₅₀ 3-18 d (laboratory and field results).Plant:In plants, rapid metabolism occurs. The overall metabolic pattern indicates hydrolysis of the ester bond, cleavage of the heterocyclic moieties into fragments which are further oxidised to CO₂.

Transport Information

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