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Enantiomeric Discrimination by Double Quantum Excited Selective Refocusing (DQ-SERF) Experiment

Baishya, Bikash and Prabhu, Uday Ramesh and Suryaprakash, N (2007) Enantiomeric Discrimination by Double Quantum Excited Selective Refocusing (DQ-SERF) Experiment. In: The Journal of Physical Chemistry B, 111 (43). pp. 12403-12410.

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Official URL: http://pubs.acs.org/doi/pdf/10.1021/jp074873s

Abstract

The differences in chemical shift anisotropies, dipolar couplings, and quadrupolar couplings of two enantiomers in the chiral liquid crystalline media are employed to visualize enantiomers. In spite of the fact that proton has high magnetic moment and is abundantly present in all the chiral molecules, $^1H$ NMR is not exploited to its full potential because of severe overlap of unresolved transitions arising from long- and short-distance couplings. Furthermore, the two spectra from R and S enantiomers result in doubling of the number of observable transitions. The present study demonstrates the application of the selectively excited homonuclear double quantum (DQ) coherence correlated to its single quantum coherence of an isolated methyl group in a chiral molecule. The DQ dimension retains only the passive couplings within the protons of the methyl group while the long-distance passive couplings are refocused, removing the overlap of central transitions, and each enantiomer displays a doublet instead of a triplet unlike in regular selective refocusing experiment. The doublet separation being different for each enantiomer results in their discrimination. The cross section taken along the single quantum dimension pertaining to each transition in the DQ dimension provides the one-dimensional spectra for each individual enantiomer with the complete removal of the overlapped transitions from the other enantiomer. The experiment is robust, the pulse sequence is easy to implement, and the methodology has been demonstrated on different chiral molecules.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to American Chemical Society.
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Division of Chemical Sciences > NMR Research Centre (Formerly SIF)
Date Deposited: 17 Dec 2008 14:26
Last Modified: 19 Sep 2010 04:52
URI: http://eprints.iisc.ernet.in/id/eprint/16532

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