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The letters rac or a bracketed plus-minus sign.
Also known as: Racemate prefix, Plus-minus prefix, rac, Racemic mixture notation
A racemic prefix says the sample is an equal mixture of both enantiomers, so it does not rotate light at all — the two halves cancel. It is a statement about a sample rather than about a molecule, which is why it cannot appear in a structure.
Denotes an equimolar mixture of two enantiomers, which is optically inactive because the rotations cancel.
Contexts: Laboratory
Describes a sample rather than a compound: there is no such thing as a racemic molecule.
Contexts: Laboratory
Is written rac-, (±)- or, in older literature, dl-, all three meaning the same thing.
Contexts: Laboratory
The three roman letters r, a and c followed by a hyphen, or a plus sign above a minus sign enclosed in round brackets.