Methomyl

Methomyl is a carbamate insecticide introduced in 1966. It is highly toxic to humans, livestock, pets, and wildlife.[3] The EU and UK imposed a pesticide residue limit of 20 µg/kg for apples and oranges.

Methomyl[1]
Skeletal formula of (E)-Methomyl
(E)-Methomyl
Space-filling model of (E)-Methomyl
Skeletal formula of (Z)-Methomyl
(Z)-Methomyl
Space-filling model of (E)-Methomyl
Names
IUPAC name
(E,Z)-methyl N-{[(methylamino)carbonyl]oxy}ethanimidothioate
Other names
Lannate, Mesomile, Methomex, Nudrin
Identifiers
CAS Number
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.037.089
PubChem CID
Properties
Chemical formula
 C5H10N2O2S
Molar mass 162.20
Appearance White crystalline solid[2]
Odor Slight, sulfur-like[2]
Density 1.2946 g/cm3
Melting point 78 to 79 °C (172 to 174 °F; 351 to 352 K)
Solubility in water
 58 g/L
Vapor pressure 0.00005 mmHg (25°C)[2]
Hazards
Flash point Noncombustible[2]
NIOSH (US health exposure limits):
PEL (Permissible)
 none[2]
REL (Recommended)
 TWA 2.5 mg/m3[2]
IDLH (Immediate danger)
 N.D.[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Methomyl is a common active ingredient in commercial fly bait, for which the label instructions in the United States warn that "It is a violation of Federal Law to use this product in a manner inconsistent with its labeling." "Off-label" uses and other uses not specifically targeted at problem insects are illegal, dangerous, and ill-advised.[4][5]

Use

Methomyl is a broad-spectrum insecticide that is used to kill insect pests.[6] Methomyl is registered for commercial/professional use under certain conditions on sites including field, vegetable, and orchard crops; turf (sod farms only); livestock quarters; commercial premises; and refuse containers. Products containing 1% Methomyl are available to the general public for retail sale, but more potent formulations are classified as restricted-use pesticides: not registered for homeowner or non-professional application.[6] However, Heliothis virescens developed a resistance to methomyl within 5 years.[7] Other species like Helicoverpa assulta also developed resistance after exposure.[8]

Trade names

Common names for methomyl include metomil and mesomile. Trade names include Acinate, Agrinate, DuPont 1179, Flytek, Kipsin, Lannate, Lanox, Memilene, Methavin, Methomex, Nudrin, NuBait, Pillarmate and SD 14999 [9]

Toxicity

In acute toxicity testing, methomyl is placed in EPA Toxicity Category I (the highest toxicity category out of four) via the oral route and in eye irritation studies.[6] It is in lower Toxicity Categories for inhalation (Category II), acute dermal effects (Category III), and acute skin irritation (Category IV). Methomyl is not likely to be a carcinogen (EPA carcinogen Category E).[6]

Ecotoxicity

Methomyl has low persistence in the soil environment, with a reported half-life of approximately 14 days.[10] Because of its high solubility in water, and low affinity for soil binding methomyl may have potential for groundwater contamination.[6][9] The estimated aqueous half-life for the insecticide is 6 days in surface water and over 25 weeks in groundwater.[9]

Synthesis

First prepare thioester

Second prepare oxime from thioester

Third prepare product from methyl isocyanate and the finished oxime.

References
  1. Merck Index, 11th Edition, 5905
  2. NIOSH Pocket Guide to Chemical Hazards. "#0387". National Institute for Occupational Safety and Health (NIOSH).
  3. Methomyl at Extension Toxicology Network
  4. Conservation Warden Warns: Fly bait to control wild animals – illegal and a bad idea (Wisconsin Department of Natural Resources)
  5. Farm stores promoted poisoning raccoons, state chemist says
  6. EPA R.E.D. FACTS - Methomyl (PDF) (Technical report). U. S. Environmental Protection Agency. December 1998. EPA-738-F-98-019.
  7. Blanco, Carlos (2012). "Heliothis virescens and Bt cotton in the United States". GM Crops & Food: Biotechnology in Agriculture and the Food Chain. 3: 201–212.
  8. Wang, Kai-Yun; Zhang, Yong; Wang, Hong-Yan; Xia, Xiao-Ming; Liu, Tong-Xian (2010-01-01). "Influence of three diets on susceptibility of selected insecticides and activities of detoxification esterases of Helicoverpa assulta (Lepidoptera: Noctuidae)". Pesticide Biochemistry and Physiology. 96 (1): 51–55. doi:10.1016/j.pestbp.2009.09.003.
  9. http://extoxnet.orst.edu/pips/methomyl.htm
  10. Howard, P. H. (1991). Handbook of Environmental Fate and Exposure Data for Organic Chemicals: Pesticides. Chelsea, MI: Lewis Publishers. pp. 3–15.
  • Methomyl in the Pesticide Properties DataBase (PPDB)
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