Diastereomeric ratio

The diastereomeric ratio, or short- dr- value (from English: diastereomeric ratio), is a modern term used in chemistry, specifically from the stereochemistry. It is used to characterize a mixture of diastereomers and increasingly replaces the obsolete term diastereomeric excess de (of English: diastereomeric excess).

In this case, a mixture of diastereomers is characterized by the ratio [ diastereomer 1]: [ diastereomer 2], wherein the diastereomers can also be present as racemates.

Analysis

Analytic methods used are mainly chromatographic methods (gas chromatography or high pressure liquid chromatography ) or NMR spectroscopy. These methods allow to measure the concentration of each diastereomer in a mixture of diastereomers individually without using a chiral stationary phase ( GC, HPLC ) or without the addition of enantiomerically pure auxiliary ( NMR: chiral shift reagent or chiral solvent). The ratio of the integrals of equivalent peaks in the chromatograms or the integrals of equivalent peaks in the NMR spectra is equal to the diastereomeric ratio.