Quiz: Remember the definition of mal de mer?


[dahy-uh-ster-ee-uh-mer, -steer-] /ˌdaɪ əˈstɛr i ə mər, -ˈstɪər-/
noun, Chemistry
either of a pair of stereoisomers that are not mirror images of each other.
Also called diastereoisomer
[dahy-uh-ster-ee-oh-ahy-suh-mer, -steer-] /ˌdaɪ əˌstɛr i oʊˈaɪ sə mər, -ˌstɪər-/ (Show IPA)
Compare enantiomer.
1935-40; dia- + stereo(iso)mer Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
Cite This Source
British Dictionary definitions for diastereoisomer


(chem) a type of isomer that differs in the spatial arrangement of atoms in the molecule, but is not a mirror image; a stereoisomer that is not an enantiomer
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Cite This Source
Encyclopedia Article for diastereoisomer

either member of a pair of substances that differ with respect to the configurations of their molecules (i.e., stereoisomers) and that lack a mirror-image relationship (i.e., are not enantiomorphs). An example is the pair consisting of either of the two optically active forms of tartaric acid (either the dextrorotatory or levorotatory form) and the optically inactive meso form of the same acid (mesotartaric acid). Unlike enantiomorphs, diastereoisomers need not have closely similar physical and chemical properties: they may differ as greatly as do structural isomers. For example, either of the optically active tartaric acids melts at 187 C (369 F), whereas mesotartaric acid melts at 143 C (290 F)

Learn more about diastereoisomer with a free trial on
Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
Cite This Source

Word of the Day

Difficulty index for diastereomer

Few English speakers likely know this word

Word Value for diastereoisomer

Scrabble Words With Friends