Mixture of diastereomers
Example of a mixture of four stereoisomers: (±) - trans -2-phenylcyclopropylamine (left, drug tranylcypromine , a racemate ) and (±) - cis -2-phenylcyclopropylamine (right). The mixture of all four stereoisomers is a mixture of diastereoisomers. Furthermore, for example, mixtures of trans - (1 R , 2 S ) -2-phenylcyclopropylamine and cis - (1 S , 2 S ) -2-phenylcyclopropylamine and / or cis - (1 R , 2 S ) -2-phenylcyclopropylamine diastereomer mixtures etc. .– The mixture of trans - (1 R , 2 S ) -2-phenylcyclopropylamine and trans - (1 S , 2 R ) -2-phenylcyclopropylamine is a mixture of enantiomers , not a mixture of diastereomers. Similarly, the mixture of cis - (1 S , 2 S ) -2-phenylcyclopropylamine and cis - (1 R , 2 R ) -2-phenylcyclopropylamine is a mixture of enantiomers, not a mixture of diastereomers.
Mixture of diastereomers is a term from chemistry , more precisely from stereochemistry .
Diastereomer mixtures are a special case of substance mixtures in which the mixture consists of two or more diastereomers . Mixtures of diastereomers should not be confused with mixtures of enantiomers - racemates or non- racemic mixtures of enantiomers.
Emergence
Mixtures of diastereomers can be formed from
- Racemates or pure enantiomers , if an additional stereogenic center with a selectivity of <100% is formed in a chemical or enzymatic reaction.
- meso compounds with a stereoselectivity of <100%
- unsymmetrical alkenes , for example through the addition of bromine, with a stereoselectivity of <100%
- symmetrical alkenes, for example through the addition of bromine, with a stereoselectivity of <100%
separation
Diastereomers have different physical and chemical properties. Therefore, mixtures of diastereoisomers can be separated by numerous methods, such as
- fractional crystallization
- fractional distillation
- fractional extraction
- Chromatography ( HPLC , gas chromatography , column chromatography , thin layer chromatography ) on an achiral phase
Of course, not every one of these separation methods is suitable for separating every mixture of diastereoisomers.
Individual evidence
- ^ Rainer Beckert, Hans-Joachim Knölker, Egon Fanghänel, Peter Metz, Wolf D. Habicher and Klaus Schwetlick: Organikum , Wiley-VCH Verlag GmbH, 23rd edition, 2009, p. 178, ISBN 978-3-527-32292- 3 .