Metolachlor

• (RS)- 2-ethyl -6-methyl -N-( 1' -methyl- 2'- methoxyethyl) chloroacetanilide

• 51218-45-2
• 87392-12-9 (S) -metolachlor
• 178961-20-1 (R) -metolachlor

In pure form, odorless, colorless-to- white liquid, brown in technical form, oily, very heavy flammable liquid

Liquid

1.12 g · cm -3

-62 ° C

100 ° C ( 0.13 Pa)

0.17 Pa ( 20 ° C)

• Very poor in water ( 0.49 g · l-1 at 25 ° C)
• Mixed with benzene, dichloromethane, hexane, methanol, octanol, xylene, toluene, dimethylformamide, 1,2-dichloroethane, cyclohexanone
• Insoluble ethylene glycol and propylene glycol

Risk

2780 mg · kg -1 ( LD50, rat, oral)

Template: Infobox chemical / molecular formula search available

Metolachlor is a mixture of four isomeric chemical compounds from the group of carboxylic acid amides and chloroacetanilides.

History

Metolachlor was developed by Ciba-Geigy. In the 1970s, the effect of ( rac) -metolachlor was observed and logged in a synthesis process and a patent. From 1978 to connect to a large extent was ( > 10,000 t per year) produced and examined from 1982, the stereoisomers individually in their effect, with the particular effectiveness of (S) -metolachlor turned out. After some experiments with catalysts of rhodium and iridium compounds, a process with an iridium - Josiphos complex ( Iridiumferrocenyldiphosphin ) was developed in 1993 for large-scale production. In the same year the patent for ( rac) -metolachlor ran out and started in 1996 the large scale production of (S) -metolachlor. Today, this is one of the most widely used herbicides in the U.S. dar. In Germany, Austria and Switzerland ( RS)- metolachlor included in any authorized plant protection products. ( S)- metolachlor is still allowed as a herbicide by the end of 2015 and included in several pesticides.

Production and representation

Metolachlor is obtained today by stereoselective synthesis. It may be obtained by reaction of 2 -ethyl -6-methyl -aniline with methoxyacetone or 2 -bromo- methoxy- propane, followed by reaction with chloroacetyl chloride.

Stereochemistry

Metolachlor comes in two enantiomeric forms ( R) - or (S ) -metolachlor, with the ( S) form is the more effective. Therefore, for some time manufacturing processes are preferred in which increased the ( S)-form is produced. This form is sold as the (S) -metolachlor, with more than 80% proportion of the ( S) form.

A special feature is that the two epimers additionally exist as atropisomers, so there are four stereoisomers of Metolachlors. Two atropisomers of (S) -metolachlor [(? R, 1 ' S) - and the ( αS, 1' S) -isomer ], the same biological effect. On the other hand the two atropisomers of (R) -metolachlor [(? R, 1 ' R ) - and ( αS, 1' R)-isomer ] are inactive.

Use

Metolachlor (often in combination with other herbicides such as atrazine, terbuthylazine or ) used as a herbicide against grasses and millet weeds in corn, soybeans, peanuts and cotton. It acts by inhibiting Elongases and geranylgeranyl pyrophosphate ( GGPP ) Zyklisierungsenzyme with gibberellins.

Safety

The use of metolachlor in decorative objects and games is not permitted. It affects very toxic to aquatic.