Return to Contents Chapter 7 : Stereochemistry Ch 7 contents

There are a couple of ways we can use to define diastereomers:

Chiral molecules that possess two (or more) chirality centers (we will define this soon) have stereoisomers that may be either enantiomers or diastereomers. Diastereomers are stereoisomers that are not mirror images.

Look at the two JSMOL images of molecules shown below and make sure you can see this, for example, look at the relative positions of the two halogens given the similar positions of the alkyl chain.

(S,R)-2-bromo-3-chlorobutane  (R,R)-2-bromo-3-chlorobutane 

Diastereomers can have quite different physical and chemical properties from one another. This is important as it allows them to be separated. Do you remember the properties of enantiomers ?

Important properties of diastereomers that you should know
  • they have different physical properties 
  • they have different chemical / biological properties

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organic chemistry © Dr. Ian Hunt, Department of Chemistry University of Calgary