Methomyl

Methomyl
IUPAC name (E,Z)-methyl N-{[(methylamino)carbonyl]oxy}ethanimidothioate
Other names Lannate, Mesomile, Methomex, Nudrin
Identifiers
CAS number	16752-77-5 Y
PubChem	5353758
Jmol-3D images	Image 1
SMILES CC(=NOC(=O)NC)SC
Properties
Molecular formula	C5H10N2O2S
Molar mass	162.21 g mol−1
Appearance	Crystals
Density	1.2946 g/cm3
Melting point	78-79 °C
Solubility in water	58 g/L
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Methomyl is a carbamate insecticide. It was introduced in 1966, but its use is restricted because of its high toxicity to humans. Its current primary use is on alfalfa for forage. 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.

Methomyl is the active ingredient in commercial fly bait granules which are mixed with a cola drink to illegally kill bothersome raccoon, skunk and opossum.

Synthesis

Methomyl can be produced by reacting 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 oxim 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 oxim. ${{\text{H}}_{\text{3}}}\text{C-N=C=O+HO-N=}\underset{\text{C}{{\text{H}}_{\text{3}}}}{\mathop{\underset{\text{ }\!\!|\!\!\text{ }}{\mathop{\text{C}}}\,}}\,\text{-S-C}{{\text{H}}_{\text{3}}}\xrightarrow{\text{C}{{\text{H}}_{\text{2}}}\text{C}{{\text{l}}_{\text{2}}}\text{,30--50 }\!\!~\!\!\text{ }\!\!{}^\circ\!\!\text{ C}}\text{Methomyl}$