Methomyl

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Methomyl[1]
Methomyl Structural Formulae .V.1.svg
Identifiers
CAS number 16752-77-5 YesY
PubChem 5353758
ChemSpider 3966 N
ChEBI CHEBI:6835 N
ChEMBL CHEMBL552761 N
Jmol-3D images Image 1
Properties
Molecular formula C5H10N2O2S
Molar mass 162.21 g mol−1
Appearance Crystals
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
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

Methomyl is a carbamate insecticide introduced in 1966. It is highly toxic to humans.[3] The EU and UK imposed a pesticide residue limit of 0.02 mg/kg for apples and oranges.[citation needed]

Methomyl is the active ingredient in commercial fly bait granules which are mixed with a cola drink to kill bothersome raccoon, skunk and opossum. Using methomyl in this "off-label" way may be against the law in some of the United States.[4][5]

Use[edit]

Methomyl is an insecticide used against Lepidopterous insect pests, and suppresses Coleopterous and some Hemipterous insect pests. It is also used as an ovicide against cotton bollworms and budworms.[6] Methomyl is registered for commercial/professional use on on a wide variety of agricultural sites including field, vegetable, and orchard crops; turf (sod farms only); and livestock quarters. Its use is also allowed on commercial premises and refuse containers. It is not registered for homeowner or nonprofessional application.[6]

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 [7]

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.[8] Because of its high solubility in water, and low affinity for soil binding methomyl may have potential for groundwater contamination.[6][7] The estimated aqueous half-life for the insecticide is 6 days in surface water and over 25 weeks in groundwater.[7]

Synthesis[edit]

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

First prepare ester

{{\text{H}}_{\text{3}}}\text{C-}\underset{\underset{\text{O}}{\mathop{\text{ }\!\!|\!\!\text{  }\!\!|\!\!\text{ }}}\,}{\mathop{\text{C}}}\,\text{-OH+HS-C}{{\text{H}}_{\text{3}}}\xrightarrow{\text{30--50 }\!\!~\!\!\text{  }\!\!{}^\circ\!\!\text{ C}\text{,-}{{\text{H}}_{2}}O}{{\text{H}}_{\text{3}}}\text{C-}\underset{\underset{\text{O}}{\mathop{\text{ }\!\!|\!\!\text{  }\!\!|\!\!\text{ }}}\,}{\mathop{\text{C}}}\,\text{-S-C}{{\text{H}}_{\text{3}}}

Second prepare oxime from ester {{\text{H}}_{\text{3}}}\text{C-}\underset{\underset{\text{O}}{\mathop{\text{ }\!\!|\!\!\text{  }\!\!|\!\!\text{ }}}\,}{\mathop{\text{C}}}\,\text{-S-C}{{\text{H}}_{\text{3}}}\text{+}{{\text{H}}_{\text{2}}}\text{NOH}\xrightarrow{-{{H}_{2}}O}\text{HO-N=}\underset{\text{C}{{\text{H}}_{\text{3}}}}{\mathop{\underset{\text{ }\!\!|\!\!\text{ }}{\mathop{\text{C}}}\,}}\,\text{-S-C}{{\text{H}}_{\text{3}}}

Third prepare product from isocyanate and oxime. {{\text{H}}_{\text{3}}}\text{C-N=C=O+HO-N=}\underset{\text{C}{{\text{H}}_{\text{3}}}}{\mathop{\underset{\text{ }\!\!|\!\!\text{ }}{\mathop{\text{C}}}\,}}\,\text{-S-C}{{\text{H}}_{\text{3}}}\xrightarrow{\text{C}{{\text{H}}_{\text{2}}}\text{C}{{\text{l}}_{\text{2}}}\text{,30--50 }\!\!~\!\!\text{  }\!\!{}^\circ\!\!\text{ C}}\text{Methomyl}

References[edit]

  1. ^ Merck Index, 11th Edition, 5905
  2. ^ CDC - NIOSH Pocket Guide to Chemical Hazards
  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 (Technical report). U. S. Environmental Protection Agency. December 1998. EPA-738-F-98-019. 
  7. ^ a b c http://extoxnet.orst.edu/pips/methomyl.htm
  8. ^ 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]