A-Level Chemistry AQA Notes

3.3.7 Optical isomerism (A-Level)

Optical isomerism (A-Level)
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Optical Isomerism
  • Optical isomers/enantiomers are species which are non-superimposable mirror images of each other. One isomer rotates plane-polarise light clockwise, and the other rotates it anticlockwise
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  • Optical isomerism is a form of stereoisomerism and occurs as a result of chirality in molecules
  • A chiral centre is a carbon atom with 4 different groups attached (it is asymmetric).
  • All amino acids except glycine have a chiral centre
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  • A 50:50 mix of the enantiomers (a racemic mixture) will have no overall effect on plane-polarised light as the effects from the two enantiomers cancel out
  • ​Racemic mixtures are formed when two achiral molecules react
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  • Racemic mixtures are also formed in reactions involving double bonds
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