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Differentiation of meso isomers from racemic mixtures with the combined use of chiral shift reagents and two‐dimensional heteronuclear correlation NMR spectroscopy
Author(s) -
Henrichs P. Mark,
Rodger Charles A.,
Caulfield Thomas,
Guo Peng
Publication year - 1995
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260331112
Subject(s) - heteronuclear molecule , chemistry , enantiomer , nuclear magnetic resonance spectroscopy , two dimensional nuclear magnetic resonance spectroscopy , reagent , intramolecular force , molecule , spectroscopy , stereochemistry , computational chemistry , organic chemistry , quantum mechanics , physics
In the presence of chiral shift reagents the enantiotopic nuclei of a pair of enantiomers become diastereotopic and have the potential to give resolved NMR signals. Similarly, the enantiotopic nuclei within a meso isomer become diastereotopic in the presence of a chiral shift reagent and may give resolved NMR signals. However, the diastereotopic nuclei of a meso isomer mixed with a chiral shift reagent, unlike those of a racemic mixture, are located in the same molecule. Their intramolecular character can be established experimentally by detection of spin‐spin splitting between them or to a common third nucleus. Comparison of the correlation peaks in a two‐dimensional, heteronuclear, multiple‐quantum correlation (HMQC) spectrum with those of a heteronuclear multiple‐bond correlation (HMBC) spectrum is an effective means of detection of coupling to a third nucleus. Two‐dimensional NMR spectroscopy was used to identify the meso form of di‐( trans ‐2‐aminocyclohexyl)amine.