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Conformational equilibria of ephedrine and pseudoephedrine and hydrogen bonding

Tsai, Helen and Roberts, John D. (1992) Conformational equilibria of ephedrine and pseudoephedrine and hydrogen bonding. Magnetic Resonance in Chemistry, 30 (9). pp. 828-830. ISSN 0749-1581. doi:10.1002/mrc.1260300905.

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Proton NMR spectra suggest that the conformation with trans vicinal hydrogens is favored for ephedrine as the free base in deuterium oxide, although in non-polar solvents, such as deuteriotrichloromethane, the gauche vicinal hydrogen conformations are favored, as has been reported previously. The conjugate acid has primarily gauche hydrogens. In contrast, the trans-hydrogen rotamers of pseudoephedrine dominate for both the non-protonated and protonated forms in deuterium oxide. Hydrogen bonding is unlikely to be as important as usually assumed in determining the conformational preferences of these substances.

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Additional Information:© 1992 John Wiley & Sons, Ltd. Received 30 December 1991; Accepted (revised) 1 May 1992. We thank Silvia Cavagnero and Dr. David Live for assistance with the NMR spectra. This research was supported by the Caltech Consortium in Chemistry and Chemical Engineering, founding members E. I. du Pont de Nemours, Eastman Kodak and Minnesota Mining and Manufacturing. Additional support was provided by the Caltech Summer Undergraduate Research Program (SURF).
Funding AgencyGrant Number
Caltech Consortium in Chemistry and Chemical EngineeringUNSPECIFIED
E. I. du Pont de Nemours and CompanyUNSPECIFIED
Eastman Kodak CorporationUNSPECIFIED
Minnesota Mining and Manufacturing CompanyUNSPECIFIED
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Subject Keywords:Proton NMR; Yicinal couplings; Conformational analysis; Hydrogen bonding; Amino alcohols; Ephedrine Pseudoephedrine
Issue or Number:9
Record Number:CaltechAUTHORS:20151002-123936548
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Official Citation:Tsai, H. and Roberts, J. D. (1992), Conformational equilibria of ephedrine and pseudoephedrine and hydrogen bonding. Magn. Reson. Chem., 30: 828–830. doi: 10.1002/mrc.1260300905
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:60715
Deposited By: Ruth Sustaita
Deposited On:02 Oct 2015 21:57
Last Modified:10 Nov 2021 22:38

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