Metolachlor Isomer Story
There has been a lot of "information" in the form of opinion papers and advertisements that has been passed around the corn belt attempting to explain the differences between metolachlor and s-metolachlor over the past year. Some of this information has mentioned Stalwart® brand metolachlor products from Sipcam Agro USA, Inc. It is time to set the record straight based upon the facts. Now you can read the rest of the story on what exactly is taking place and why Stalwart brand metolachlor products perform when used according to their labels.
What is metolachlor?
Metolachlor is an acetanilide herbicide with the following chemical structure:
What are isomers?
Isomers are two or more chemical compounds that have the same number of each kind of atom, but differ in the way the atoms are arranged. Because the atom arrangement varies, isomers generally differ from each other in both their physical properties and their chemical behavior.
Does metolachlor have any isomers?
Yes, all metolachlor-based products have four isomers. Simply put, there are two locations on the metolachlor molecule where substituents trade places. Below is an illustration showing where these two locations (A and B) are and whether the methyl group (CH3) is arranged in position 1 or position 2 at each location. The position of the methyl group around the carbon atom at the B position defines whether the metolachlor isomer is in the S or the R configuration, not the A position.
What metolachlor isomers does Stalwart contain?
Stalwart® brands contain a 50/50 mixture ratio of S-isomer pairs and R-isomer pairs. The active ingredient containing this 50/50 mixture ratio is referred to as metolachlor.
What metolachlor isomers does Dual II Magnum® contain?
Dual II Magnum contains a mixture of S and R isomer pairs in an 88/12-mixture ratio. The active ingredient containing the 88/12-mixture ratio is referred to as s-metolachlor.
What does all of this mean in terms of weed control?
At labeled rates, Stalwart brand products control weeds as effectively as other pre-emergence herbicides in the market today. See the Field Trial Data Summary for test results.
Related Information
Dual II Magnum is a registered trademark of Syngenta Crop Protection.