What is a racemate?
A racemic mixture, also called a racemate, contains equal amounts of the two enantiomers of a chiral compound.
Therefore, half of the mixture consists of one enantiomer and half consists of its non-superimposable mirror image.
| Component of a racemate | Amount present |
|---|---|
| One enantiomer | 50% |
| Mirror-image enantiomer | 50% |
Each pure enantiomer is optically active. The important feature of a racemate is that the two enantiomers are present in exactly equal amounts, so their opposite effects on plane-polarised light balance one another.
One enantiomer
Rotates plane-polarised light in one direction.
Amount in a racemate: 50%
Mirror-image enantiomer
Rotates plane-polarised light by the same amount in the opposite direction.
Amount in a racemate: 50%
Exam Tip: To define a racemic mixture precisely, state that it contains equal amounts of the two enantiomers. Describing it only as a mixture of optical isomers is incomplete.