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Article

One-Dimensional 13C NMR Is a Simple and Highly Quantitative Method for Enantiodiscrimination

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Molecules 2018, 23(7), 1785; https://doi.org/10.3390/molecules23071785
Received: 21 June 2018 / Revised: 13 July 2018 / Accepted: 17 July 2018 / Published: 20 July 2018
(This article belongs to the Special Issue Stereogenic Centers)
The discrimination of enantiomers of mandelonitrile by means of 1D 13C NMR and with the aid of the chiral solvating agent (S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol (TFAE) is presented. 1H NMR fails for this specific compound because proton signals either overlap with the signals of the chiral solvating agent or do not show separation between the (S)-enantiomer and the (R)-enantiomer. The 13C NMR method is validated by preparing artificial mixtures of the (R)-enantiomer and the racemate, and it is shown that with only 4 mg of mandelonitrile a detection limit of the minor enantiomer of 0.5% is obtained, corresponding to an enantiomeric excess value of 99%. Furthermore, the method shows high linearity, and has a small relative standard deviation of only 0.3% for the minor enantiomer when the relative abundance of this enantiomer is 20%. Therefore, the 13C NMR method is highly suitable for quantitative enantiodiscrimination. It is discussed that 13C NMR is preferred over 1H NMR in many situations, not only in molecules with more than one chiral center, resulting in complex mixtures of many stereoisomers, but also in the case of molecules with overlapping multiplets in the 1H NMR spectrum, and in the case of molecules with many quaternary carbon atoms, and therefore less abundant protons. View Full-Text
Keywords: enantiomers; Pirkle’s alcohol; TFAE; qNMR; mandelonitrile; CSA; chirality; chiral solvating agent enantiomers; Pirkle’s alcohol; TFAE; qNMR; mandelonitrile; CSA; chirality; chiral solvating agent
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MDPI and ACS Style

Lankhorst, P.P.; Van Rijn, J.H.J.; Duchateau, A.L.L. One-Dimensional 13C NMR Is a Simple and Highly Quantitative Method for Enantiodiscrimination. Molecules 2018, 23, 1785. https://doi.org/10.3390/molecules23071785

AMA Style

Lankhorst PP, Van Rijn JHJ, Duchateau ALL. One-Dimensional 13C NMR Is a Simple and Highly Quantitative Method for Enantiodiscrimination. Molecules. 2018; 23(7):1785. https://doi.org/10.3390/molecules23071785

Chicago/Turabian Style

Lankhorst, Peter P., Jozef H. J. Van Rijn, and Alexander L. L. Duchateau. 2018. "One-Dimensional 13C NMR Is a Simple and Highly Quantitative Method for Enantiodiscrimination" Molecules 23, no. 7: 1785. https://doi.org/10.3390/molecules23071785

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