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Badania układów racemat/enancjomer oraz określanie nadmiaru enancjomerycznego za pomocą wysokorozdzielczej spektroskopii NMR w cieczy i w ciele stałym

Tadeusiak E. J.

Wiadomości Chemiczne

2003

[Z] 57, 5-6

367--389

Over the past decade there has been a surge of interest in enantioselective synthesis which has led to find convenient metods of measuring enantiomeric purity or enantiomeric excess of many compounds. The enantiomeric excess can be determined by the following principal methods: (a) chiroptical, (b) chromatography (GS, HPLC, TLC ), (c) isotopic dilution, (d) kinetics, (e) electrophoresis, (f) calorimetry, (g) nuclear magnetic resonance. In this paper there are presented studies, which were performed in aim to determine of ee by NMR in liquid and solid state. Determination of enantiomeric purity using NMR in liquid requires the intervention of a chiral auxiliary to convert an enantiomeric mixture into a mixture of diastereomers. Three types of chiral auxiliary are widely used. Chiral derivatising agents (CDAs) form diastereomers while chiral solvating agents (CSAs) and chiral lanthanide shift reagents (CLSRs) form diastereomeric complexes in situ with the substrate enantiomers. In recent years Solid–State NMR (SS NMR) has emerged as a powerful tool for the analysis of solids. In particular the ODESSA (One Dimensional Exchange Spectroscopy by Sideband Alternation) technique permit to recognize differences between enantiomers and racemates as well to assess the enantiomeric excess.