Metolachlor

Metolachlor is an organic compound that is widely used as an herbicide. It is a derivative of aniline and is a member of the chloroacetanilide family of herbicides. It is highly effective toward grasses.

Metolachlor^[1]

Names
IUPAC name (RS)-2-Chloro-N-(2-ethyl-6-methyl-phenyl)-N-(1-methoxypropan-2-yl)acetamide
Other names Dual, Pimagram, Bicep, CGA-24705, Pennant.
Identifiers
CAS Number	51218-45-2 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:6902 N
ChEMBL	ChEMBL1884974 N
ChemSpider	4025 Y
ECHA InfoCard	100.051.856
KEGG	C10953 Y
PubChem CID	4169
UNII	X0I01K05X2 Y
CompTox Dashboard (EPA)	DTXSID4022448
InChI InChI=1S/C15H22ClNO2/c1-5-13-8-6-7-11(2)15(13)17(14(18)9-16)12(3)10-19-4/h6-8,12H,5,9-10H2,1-4H3 Y Key: WVQBLGZPHOPPFO-UHFFFAOYSA-N Y InChI=1/C15H22ClNO2/c1-5-13-8-6-7-11(2)15(13)17(14(18)9-16)12(3)10-19-4/h6-8,12H,5,9-10H2,1-4H3 Key: WVQBLGZPHOPPFO-UHFFFAOYAS
SMILES CCc1cccc(c1N(C(C)COC)C(=O)CCl)C
Properties
Chemical formula	C15H22ClNO2
Molar mass	283.80 g·mol−1
Appearance	Off-white to colorless liquid
Density	1.1 g/mL
Boiling point	100 °C (212 °F; 373 K) at 0.001 mmHg
Solubility in water	530 ppm at 20 °C
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	[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

Agricultural use

Metolachlor was developed by Ciba-Geigy. Its acts by inhibition of elongases and of the geranylgeranyl pyrophosphate (GGPP) cyclases, which are part of the gibberellin pathway. It is used for grass and broadleaf weed control in corn, soybean, peanuts, sorghum, and cotton. It is also used in combination with other herbicides.

Metolachlor is a popular herbicide in the United States.^[3] As originally formulated metolachlor was applied as a racemate, a 1:1 mixture of the (S)- and (R)-stereoisomers. The (R)-enantiomer is less active, and modern production methods afford a higher concentration of S-metolachlor, thus current application rates are far lower than original formulations.

Production and basic structure

Metolachlor is produced from 2-ethyl-6-methylaniline (MEA) via condensation with methoxyacetone. The resulting imine is hydrogenated to give primarily the S-stereoisomeric amine. This secondary amine is acetylated with chloroacetylchloride. Because of the steric effects of the 2,6-disubstituted aniline, rotation about the aryl-C to N bond is restricted. Thus, both the (R)- and the (S)-enantiomers exist as atropisomers. Both atropisomers of (S)-metolachlor exhibit the same biological activity.^[4]

The four stereoisomers of metolachlor

Safety and ecological effects

The European Chemicals Agency classified metolachlor as a suspected human carcinogen (Carcinogen category 2) in 2022.^[5] The United States Environmental Protection Agency (US EPA) has classified Metolachlor as a Group C, possible human carcinogen, based on liver tumors in rats at the highest dose tested (HDT).^[6][7] Evidence of the bioaccumulation of metolachlor in edible species of fish as well as its adverse effect on the growth and development has raised concerns on its effects on human and environmental health. For example, products with this active ingredient are restricted to professional licensed applicators in the U.S. state of Massachusetts.^[8] Though there is no set maximum concentration (maximum contaminant level, MCL) for metolachlor that is allowed in drinking water, the US EPA does have a health advisory level (HAL) of 0.525 mg/L. Metolachlor has been detected in ground and surface waters in concentrations ranging from 0.08 to 4.5 parts per billion (ppb) throughout the U.S.^[9]

Metolachlor induces cytotoxic and genotoxic effects in human lymphocytes.^[10] Genotoxic effects have also been observed in tadpoles exposed to metolachlor.^[11] Evidence also reveals that metolachlor affects cell growth. Cell division in yeast was reduced,^[12] and chicken embryos exposed to metolchlor showed a significant decrease in the average body mass compared to the control.^[13]

See also

• Acetochlor
• Alachlor