Methomyl

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Methomyl[1]
Methomyl Structural Formulae .V.1.svg
Identifiers
CAS number 16752-77-5 YesY
PubChem 5353758
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 78-79 °C
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. It was introduced in 1966, but its use is restricted because of its high toxicity to humans.[3] Its current primary use is on alfalfa for forage.[4] The EU and UK have imposed these restrictions by allowing a maximum pesticide residue limit of 0.02 mg/kg for apples and oranges.[citation needed] 0.02 mg/kg is the limit of detection.

It has been found in residues on vegetables and spices in Thailand exceeding safety standards in 2012, due to not being listed on the Dangerous Substances Act, along with carbofuran, dicrotophos and EPN.[5]

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. [6][7]

Synthesis[edit]

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

First preparing 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 preparing 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 preparing 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. ^ Methomyl at PAN Pesticide Database
  5. ^ "Cancer-causing chemical residues found in vegetables". Bangkok Post. 12/07/2012. 
  6. ^ Conservation Warden Warns: Fly bait to control wild animals – illegal and a bad idea (Wisconsin Department of Natural Resources)
  7. ^ Farm stores promoted poisoning raccoons, state chemist says

External Links[edit]