Methomyl

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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
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.037.089
Properties
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)
58 g/L
Vapor pressure 0.00005 mmHg (25°C)[2]
Hazards
Flash point Noncombustible[2]
US health exposure limits (NIOSH):
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).
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Infobox references

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 0.02 mg/kg for apples and oranges.[citation needed]

Methomyl is a common active ingredient in commercial fly bait, for which the label instructions 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[edit]

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[edit]

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[edit]

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[edit]

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[edit]

Methomyl can be produced by reaction of methyl isocyanate and methylthioacetaldoxime (also known as methomyl oxime).

First prepare ester

Methomyl Synthesis 1 of 3 V1.svg

Second prepare oxime from ester

Methomyl Synthesis 2 of 3 V1.svg

Third prepare product from isocyanate and oxime.

Methomyl Synthesis 3 of 3 V1.svg

References[edit]

  1. ^ Merck Index, 11th Edition, 5905
  2. ^ a b c d e f g "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. ^ a b c d e 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 and 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. ^ a b c 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.

External links[edit]

  • Methomyl in the Pesticide Properties DataBase (PPDB)