Optical Purity Determination and ¹H NMR Spectral Simplification with Lanthanide Shift Reagents: Glutethimide, 3-Ethyl-3-phenyl-2, 6-piperidinedione, 1

Authors: Eberhart, Suzanne; Rothchild, Robert

Source: Applied Spectroscopy, Volume 37, Issue 3, Pages 219-300 (May/June 1983) , pp. 292-296(5)

Publisher: Society for Applied Spectroscopy

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Abstract:

The 60 MHz ¹H NMR spectra of racemic glutethimide, 1, have been studied with the chiral shift reagent, tris[3-(trifluoro-methylhydroxymethylene)-d-camphorato] europium (III), 2, and the achiral tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium (III), 3. Appreciable values of the enantiomeric shift difference, ΔΔδ, were observed at relatively low molar ratios of 2:1 for the CH₃ group in CDCl₃ solution at 28°C. Optical purity determinations should easily be carried out by using this absorption with a 2:1 ratio of approximately 0.25; 3 to 5% of one enantiomer should be detectable in a sample. Lanthanide-induced line broadening was relatively low, thereby facilitating these measurements. A substantial ΔΔδ was also observed for the ortho hydrogens of the aromatic ring and the NH. For example, at a 2:1 ratio of 0.254, the CH₃ resonance displayed a value of ΔΔδ of 7.3 Hz (0.12 δ) and was free of overlap with the absorptions of the shift reagent, 2. The relative slopes of the plots of induced shift, Δδ, vs molar ratios of 2:1 or 3:1, as well as values of coupling constants, support assignments for the proton absorptions of the aromatic ring.

Keywords: Glutethimide optical purity by NMR, analysis for; Methods, analytical; NMR

Document Type: Research article

DOI: http://dx.doi.org/10.1366/0003702834634479

Affiliations: 1: City University of New York, John Jay College of Criminal Justice, Science Department, 445 West 59th Street, New York, New York 10019-1199

Publication date: 1983-05-01

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