Quasiracemat method
The quasiracemate method is a method developed by Arne Fredga (1902–1992) in the 1960s for the thermoanalytical determination of the configuration of an enantiomer .
background
In the solid state, a racemic mixture can exist either as a racemic compound , as a conglomerate or as a pseudoracemate . By mixing pure enantiomers with chemically similar enantiomers, so-called Quasienantiomeren , such as enantiomers of the chloro and bromo succinic acid , the same Racematarten potentially be obtained. A quasi-acemate is a 1: 1 racemic combination of quasi-enantiomers. Link formation only occurs between enantiomers of opposite configuration .
The various quasiracemic forms can be distinguished by recording the melting point curves. Depending on whether a quasiracemic compound, a conglomerate or a pseudoracemate is present, a characteristic melting point curve is obtained. If the absolute configuration of one of the enantiomers is known, the absolute configuration of the unknown enantiomer can be determined. The method has been used successfully for various groups of substances, such as organophosphorus compounds.
Individual evidence
- ↑ Wolfgang Bähr, Hans Theobald: Organic stereochemistry. Springer Verlag, 1973, ISBN 3-540-06339-0 , pp. 92-93.
- ↑ A. Fredga: Steric correlations by the quasi-racemate method. In: Tetrahedron. 8, 1960, pp. 126-144, doi : 10.1016 / S0040-4020 (01) 93339-3 .
- ^ Leopold Horner, Helmut Winkler: Organophosphorus compounds, XLVII. Determination of the absolute configuration of (+) - methyl-n-propyl-phenyl-phosphine by asymmetric synthesis. In: Justus Liebig's Annals of Chemistry. 685, 1965, pp. 1-10, doi : 10.1002 / jlac.19656850102 .