Vamidothion Chemical Properties

Melting point:

35.5°C

Boiling point:

72.8°C

Density 

1.240±0.06 g/cm3(Predicted)

vapor pressure 

9×10^-6 Pa (est.)

Flash point:

2 °C

storage temp. 

0-6°C

Water Solubility 

4,000,000 mg l^-1

pka

15.22±0.46(Predicted)

CAS DataBase Reference

2275-23-2(CAS DataBase Reference)

NIST Chemistry Reference

Phosphorothioic acid, o,o-dimethyl s-[2-[[1-methyl-2-(methylamino)-2-oxoethyl]thio]ethyl] ester(2275-23-2)

EPA Substance Registry System

Vamidothion (2275-23-2)

Safety Information

Hazard Codes 

T;N,N,T,Xn,F

Risk Statements 

21-25-50-36-20/21/22-11

Safety Statements 

36/37-45-61-16

RIDADR 

UN 2811

WGK Germany 

2

RTECS 

TF7900000

HazardClass 

6.1(b)

PackingGroup 

III

Hazardous Substances Data

2275-23-2(Hazardous Substances Data)

Toxicity

LD50 oral in rabbit: 160mg/kg

MSDS

• Language:English Provider:Dimethyl phosphorothioate 2-((2-mercaptoethyl)thio)-N-methylpropionamide S-ester

Vamidothion Usage And Synthesis

Description

Vamidothion is a colorless crystalline substance,. It is readily soluble in water (4 kg/L) and most organic solvents except aliphatic hydrocarbons. Log Kow = 0.12. It decomposes in strong alkaline and acidic media.

Uses

Vamidothion is a phosphorothioic insecticide for apples and potatoes.

Uses

Vamidothion is a systemic insecticide used to control Homoptera in cotton, fruit and rice.

Definition

ChEBI: An organic thiophosphate that is N-methyl-2-[(2-sulfanylethyl)sulfanyl]propanamide in which the thiol group has been converted to the corresponding O,O-dimethyl thiophoshate. Formerly used as an inse ticide and acaricide, it is no longer approved for use within the European Union.

Pharmacology

Pyriproxyfen formulations demonstrate persistent efficacy. For example, a water-based 5.3% pyriproxyfen spot-on formulation applied to cats was reported to completely prevent the hatching of flea eggs for at least 46 days after treatment and continued to provide greater than 96% control until day 60 (57). Because pyriproxyfen is efficacious at very low concentrations, trace amounts of the chemical, when transferred from treated pets to their environments, are sufficient to inhibit the development of larvae.

Metabolic pathway

Vamidothion is mainly metabolised via oxidation to its sulfoxide; further oxidation to the corresponding sulfone has been observed in houseflies but occurs much less readily than with other thioether-containing organophosphates (e.g. phorate). The sulfoxide is then hydrolysed via P-S and C-S bond cleavage to give the thiol or hydroxyl derivatives and dimethyl phosphate and O,O-dimethyl phosphorothioate respectively. O-Demethylation apparently occurs as a major degradation process in plants but has not been observed in soil or in animals. N-Demethylation and hydrolysis to the corresponding carboxylic acid, such as occurs with dimethoate, does not apparently happen in the case of vamidothion.

Degradation

Vamidothion is decomposed in strongly acidic or alkaline media (PM). Barceld et al. (1993) examined the photolysis of vamidothion in water containing 2-4% methanol and 5% acetone as a photosensitiser irradiated by a xenon arc (suntest) lamp. Metabolites were analysed and characterised by HPLC, thermospray MS and UV (diode array) spectra. The main degradation product identified was vamidothion sulfoxide (2). This product of vamidothion photolysis is shown in Scheme 1.

Toxicity evaluation

The acute oral LD₅₀ for rats is 64–105 mg/kg. Inhalation LC50 (4 h) for rats is 1.73 mg/L air. ADI is 8 μg/kg b.w.

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