BRAINCAKERacemic Mixtures
A racemic mixture (or racemate) is a mixture containing equal amounts (equimolar amounts) of the two enantiomers of a chiral compound.
Each enantiomer rotates plane-polarised light by the same angle but in the opposite direction. In a racemic mixture the two rotations cancel each other out, so the mixture has no effect on plane-polarised light. A racemic mixture is therefore optically inactive.
Be careful to distinguish two kinds of optically inactive sample:
• an achiral compound is inactive because its molecules have no chiral centre;
• a racemic mixture is inactive even though every molecule is chiral, because the two enantiomers are present in equal amounts.
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Key terms in this lesson
- enantiomer
- One of a pair of optical isomers that are non-superimposable mirror images of each other.
More in Optical Isomerism
- Chirality
- Optical Isomers
- Plane-Polarised Light
- Racemates from Nucleophilic Addition
- Identifying Chiral Centres
All 6 lessons in Optical Isomerism · All AQA A-level Chemistry topics