Submitted to: Annual Experimental Nuclear Magnetic Resonance Conference
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2000
Publication Date: N/A
Conformational changes are known to occur in mixtures between structurally similar labile diastereoisomers. In principle, such changes could also occur between structurally less similar diastereoismers. Metolachlor, a pesticide with a molecular weight of 283.8, exists as a racemic mixture of two sets of enantiomers. Recent NMR research has demonstrated chemical environments under which metolachlor is conformationally labile. Previous research has shown that its structural analog alachlor is also conformationally labile. Alachlor however has no chiral center. Conformational changes were not detected in binary mixtures between structurally similar metolachlor and alachlor in a wide variety of solvents and solvent mixtures. In contrast, in binary mixtures of the structurally quite dissimilar metolachlor and L-ephedrine, each readily changed conformations. L-Ephedrine is a conformationally labile compound with a molecular weight of 165.2 and is one of four commercially available diastereoisomers. Conformational changes were observed at structurally specific sites. Interactions involving multiple chiral sites appear to be an essential component for selective conformational changes to occur within and/or between low molecular weight compounds.