Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 7, 1999
Publication Date: N/A
Interpretive Summary: The envirionmental fate of pesticides depends upon their interaction with the local chemical environment at the molecular level. Different chemical forms of the same molecular structure often have very different physical characteristics. Information identifying which chemical forms are present and under what conditions they are stable is essential to be able to explain how to increase or retard the retention of pesticides at specific locations. It is also important in predicting how long the pesticide will remain in the environment, and where in the environment it will end up.
Metolachlor exists in multiple, different stable conformations in solution. Assignment of the NMR frequencies to chemical structure is a prerequisite to understanding the behavior of individual conformations. 1H- and 13C-NMR experiments of metolachlor in different chemical environments identified the labile sites of metolachlor and environments that influence confrontational/configurational changes. Within very specific chemical environments, metolachlor atropisomers aS,12S (aR,12R) and aR,12S (aS,12R) freely interchange and consequently the multiple conformations also interchange. The changes in chemical environments, which most alter the conformations and molecular dynamics of metolachlor, identify the most critical components affecting its environmental fate. These results enable a structural interpretation of conformational changes on binding to environmental substrates.