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Abstract
The 60 MHz H NMR spectra for the herbicide, diclofop methyl, 1, have been studied in CDCl3 solution at 28±1° with the added achiral lanthanide shift reagent (LSR) tris (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium(III), Eu (FOD)3, 2, and with the chiral LSRs, tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorato]europium(III)3, Eu(HFC)3, 3, and tris[3-(trifluoromethylhydroxymethylene)-(+)-camphorato]europium(III), Eu(FACAM)3, 4. Both 2 and 3 produced substantial lanthanide-induced shifts (LIS) consistent with predominant LSR binding at the ester carbonyl. Much smaller LIS magnitudes were observed with 4. Modest enantiomeric shift differences (ΔΔδ) were elicited with 3 for the OCH3 and the CCH3 resonances of 1. The former signal appears to offer greatest potential for the direct determination of enantiomeric excess of samples of 1, with 3:1 molar ratios ca. 0.3–0.4 resulting in valley heights as low as 33% of the average peak heights of the OCH3 signals of the two enantiomers.