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The Metolachlor Herbicide: An Exercise in Today's Stereochemistry

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Albrecht Mannschreck

Department of Organic Chemistry, University of Regensburg, D-93040 Regensburg, Germany

Erwin von Angerer

Department of Pharmacy, University of Regensburg, D-93040 Regensburg, Germany

J. Chem. Educ., 2009, 86 (9), p 1054

DOI: 10.1021/ed086p1054

Publication Date (Web): September 1, 2009

Section:

History, Education, and Documentation

Abstract

Metolachlor is one of the most widely used agents registered for the protection of many cultivated plants against weeds. Because of axial and central chirality, this molecule forms four stereoisomers, the investigation of which by ¹H NMR and chromatography is described. It is shown that the isomers do not interconvert at room temperature. Non-enantioselective and enantioselective preparations on industrial scales, developed by the Syngenta Company, are given, including the composition of the catalyst used for an enantioselective hydrogenation step. The bioactivities of the four separated species are discussed. The mixture of the two stereoisomers with stronger biological effects, commonly designated (S)-metolachlor, has largely replaced the 1:1:1:1 mixture in practical agriculture. The load to the environment diminishes by using a lower dosage of (S)-metolachlor instead of a higher dosage of the 1:1:1:1 mixture. The present article exemplifies several general stereochemical aspects that are placed together in the conclusion of the article.

Keywords (Audience):

Second-Year Undergraduate

Keywords (Domain):

Organic Chemistry

Keywords (Pedagogy):

Textbooks / Reference Books

Keywords (Subject):

Agricultural Chemistry

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This article has been cited by 1 ACS Journal articles (1 most recent appear below).

A Simple Method To Determine the R or S Configuration of Molecules with an Axis of Chirality
Cunde Wang, Weiming Wu
Journal of Chemical Education2011 88 (3), 299-301
- A Simple Method To Determine the R or S Configuration of Molecules with an Axis of Chirality
  Cunde Wang, Weiming Wu
  Journal of Chemical Education2011 88 (3), 299-301
  A simple method for the R or S designation of molecules with an axis of chirality is described. The method involves projection of the substituents along the chiral axis, utilizes the Cahn−Ingold−Prelog sequence rules in assigning priority to the ...
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