Omethoate Chemical Properties

Melting point:

-27.9°C

Boiling point:

135°C

Density 

1.3200

vapor pressure 

3.3×10^-3Pa (20 °C)

Flash point:

100 °C

storage temp. 

0-6°C

solubility 

Chloroform (Slightly), Ethyl Acetate (Slightly), Methanol (Slightly)

Water Solubility 

Miscible

pka

14.40±0.46(Predicted)

form 

liquid

BRN 

1785256

Stability:

Hygroscopic

CAS DataBase Reference

1113-02-6(CAS DataBase Reference)

NIST Chemistry Reference

Omethoate(1113-02-6)

EPA Substance Registry System

Omethoate (1113-02-6)

Safety Information

Hazard Codes 

T+;N,N,T+,T

Risk Statements 

21-25-50

Safety Statements 

1/2-23-36/37-45-61

RIDADR 

3018

WGK Germany 

3

RTECS 

TF8050000

HazardClass 

6.1(a)

PackingGroup 

II

HS Code 

29309090

Hazardous Substances Data

1113-02-6(Hazardous Substances Data)

Toxicity

LD50 oral in rabbit: 50mg/kg

MSDS

• Language:English Provider:O,O-Dimethyl S-methylcarbamoylmethyl phosphorothioate

Omethoate Usage And Synthesis

Uses

Omethoate is a systemic insecticide used for the control of (mostly) sucking insects and mites in a wide variety of crops.

Uses

Insecticidal, acaricidal, and fungicidal combinations of carboxamides and other pesticides.

Definition

ChEBI: Omethoate is an organic thiophosphate and an organothiophosphate insecticide. It has a role as an EC 3.1.1.7 (acetylcholinesterase) inhibitor, an acaricide and an agrochemical. It is functionally related to a N-methyl-2-sulfanylacetamide.

Contact allergens

Contact dermatitis from omethoate-dimethoxon is rare.

Metabolic pathway

Omethoate is the P=O analogue (oxon) of dimethoate. Dimethoate is metabolised via oxidative desulfuration to omethoate which is the active anti-acetylcholinesterase metabolite. This biotransformation occurs in all media: hence the metabolic pathways of both compounds have much in common. However, degradative pathways acting directly on dimethoate such as O-demethylation, N-demethylation and hydrolysis of the amide function mean that the balance between activation and degradative metabolism will influence their respective selective toxicities. In mammals there are two main routes of degradation: (i) glutathione transferase mediated O-demethylation (ii) hydrolysis to N-methylthioglycolamide which is S-methylated by S-adenosylmethionine and subsequently thiooxidised. In soil and plants the N-methylthioglycolamide moiety formed from the hydrolysis of omethoate undergoes a complex series of C₁, C₂ and C₃ biotransformations ultimately leading to oxalate and citrate respectively and total degradation to C0₂. The information reported below is derived largely from an evaluation prepared by the UK MAFF Pesticide Safety Directorate (PSD, 1993).

Metabolism

Orally administered omethoate to rats is rapidly metabolized and excreted in the urine; the main metabolites are O-demethylomethoate and N-methyl-2- methylsulfinylacetamide. O-Demethylation and hydrolysis of the P?S bond are main degradation routes both in mammals and plants. Omethoate is rapidly degraded in soils with DT₅₀ of a few days.

Degradation

Omethoate was slowly hydrolysed in acidic media but more rapidly under alkaline conditions. The half-lives for hydrolysis at pH 4,7, and 9 were 102 days, 17 days and 28 hours, respectively (PM). Omethoate does not absorb light at wavelengths above 250 nm and it is thus unlikely to be subject to photodecomposition. An aqueous solution of omethoate was irradiated for 14 hours with a high pressure filtered mercury vapour lamp without detectable photolysis occurring (PSD, 1993).

Toxicity evaluation

The acute oral LD₅₀ for rats is about 25 mg/kg. Inhalation LC50 (4 h) for rats is 0.3 mg/L air. ADI is 0.3 μg/kg b.w.

Omethoate(1113-02-6)Related Product Information

• Phosmet
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