Abstract
The 60 MHz <sup>1</sup>H NMR spectra of racemic ethotoin, <i>a</i>, have been studied with the achiral shift reagent tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium (III), <i>b</i>, and the chiral tris[3-(trifluoromethylhydroxymethylene)-<i>d</i>-camphorato] europium (III), <i>c</i>. Appreciable values of the enantiomeric shift difference, ΔΔδ, were observed for the NH, CH<sub>3</sub>, CH, and <i>ortho</i> aryl protons in CDCl<sub>3</sub> solutions at 28°C with the use of samples about 0.45 molal in <i>a</i>. Optical purity assays should be feasible with the use of the NH or CH<sub>3</sub> absorptions that display ΔΔδ of 22.4 and 7.0 Hz, respectively, at a <i>c:a</i> molar ratio of about 0.3, with the former resonance being optimal. With a <i>c:a</i> ratio between 0.4–0.5, the methine proton can be used, with ΔΔδ 11–13 Hz. Results are interpreted in terms of major coordination of the europium at the C-2 oxygen.
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