What does diastereomer mean?
A diastereomer is one of two or more chemical compounds that share the same molecular formula and the same connectivity of atoms but differ in their three-dimensional spatial arrangement in a way that makes them non-superimposable and not mirror images of one another. The term belongs to stereochemistry, the branch of chemistry concerned with how the geometry of molecules affects their behaviour. Diastereomers typically display distinct physical properties — different melting points, boiling points, and solubilities — as well as different chemical reactivities, which allows chemists to separate them by ordinary laboratory techniques such as crystallization or chromatography. This contrasts with enantiomers, their mirror-image counterparts, which share nearly all physical properties except how they interact with polarized light and other chiral substances. Diastereomers are central to pharmaceutical science, since drugs containing multiple stereocentres may exist as several diastereomers whose biological effects can differ markedly. The related forms 'diastereomeric' and 'diastereomerism' extend the concept into adjectival and abstract usage.
nounA stereoisomer of a compound that is not a mirror image of the other stereoisomer; one of two or more compounds with the same molecular formula and sequence of bonded atoms but differing three-dimensional arrangements that are not mirror images.
- Chemistry: one of two or more stereoisomers that are not mirror images of each other.
"The synthesis produced a mixture of diastereomers, which the chemists separated by chromatography."
"Because the two diastereomers had different solubilities, they were separated by simple crystallization."
"In carbohydrate chemistry, sugars such as glucose and galactose are diastereomers that differ in configuration at only some of their stereocentres."
The plural is standard and common, especially in phrases like 'a mixture of diastereomers'; the British spelling 'diastereoisomer' (plural 'diastereoisomers') also occurs.
"The reaction gave four diastereomers in unequal amounts."
Diastereomers have identical formulas and bonding yet behave like different chemicals — they can even differ in melting point and taste.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of diastereomer
Diastereomer was coined in the late nineteenth century from the Greek prefix dia- ('through, apart') combined with stereos ('solid') and meros ('part'), paralleling the earlier formation of 'isomer' from Greek isos ('equal'). It arose within the emerging discipline of stereochemistry following Jacobus van't Hoff and Joseph Le Bel's tetrahedral model of carbon in the 1870s, which gave chemists a structural language for describing non-mirror-image stereoisomers. Its sibling terms 'enantiomer' (from Greek enantios, 'opposite'), 'isomer', 'polymer', and 'monomer' all share the same Greek root -meros, meaning 'part'.
Related word forms
How diastereomer is actually used
Strictly technical vocabulary used in organic chemistry, biochemistry, and pharmacology; rarely encountered outside scientific writing. Often used attributively in its adjective form 'diastereomeric' before nouns like 'mixture' or 'excess'.
Easily confused with diastereomer
Enantiomers are mirror-image stereoisomers of each other, whereas diastereomers are stereoisomers that are not mirror images.