Advanced Topic 749 of 1102 Organic Chemistry
Diastereomers
Stereoisomers that are not mirror images of each other.
In-depth explanation of Diastereomers
Diastereomers are stereoisomers that are not mirror images of each other, which occurs when a molecule has two or more stereocentres and some but not all of them are inverted. Unlike enantiomers, diastereomers have different physical properties such as melting point, boiling point, solubility and chromatographic behaviour, so they can be separated by ordinary methods like distillation or crystallization. A molecule with n stereocentres can have up to 2 to the power n stereoisomers, but meso forms reduce this number. Diastereomers are common among sugars and many natural products.
Going deeper: Diastereomers
Key ideas: Diastereomers are stereoisomers that are not mirror images, such as cis-trans isomers or molecules with multiple stereocentres where only some are inverted. They have different melting points, solubilities and reactivities, so ordinary methods can separate them. A compound with n stereocentres has up to 2 to the n stereoisomers, in enantiomer pairs, the rest being diastereomers.
Common mistakes and connections: Students often think inverting any one stereocentre gives an enantiomer; only inverting all of them does. Epimers are diastereomers differing at one centre, such as glucose and galactose at C4. Links to Fischer projections, resolution through diastereomeric salts, and sugar chemistry.
Visualization of Diastereomers
Tartaric acid diastereomers are not mirror images and so differ in properties: melting point 170 C for the (+)-form and 140 C for meso. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Erythrose and threose are diastereomers because they differ in the configuration of only one of their two stereocentres.
Frequently asked questions about Diastereomers
What is Diastereomers?
Stereoisomers that are not mirror images of each other.
Is Diastereomers a beginner, intermediate or advanced topic?
Diastereomers is a advanced topic in Organic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Diastereomers?
Study these earlier topics in Organic Chemistry first: E-Z Notation, Chirality, Enantiomers.
What comes after Diastereomers?
The next topics in Organic Chemistry are Meso Compounds and Racemic Mixture.
Can I practise Diastereomers with quizzes?
Yes. The interactive lesson includes a self-check question on Diastereomers, and the Organic Chemistry quiz draws on every topic in this area.
Where Diastereomers fits in Organic Chemistry
Diastereomers is topic 21 of 148 in Organic Chemistry.