Optical Isomers (OCR A Level Chemistry A): Revision Note

Optical Isomers & Chirality

Optical isomerism

• Stereoisomers are molecules that have the same structural formula but have the atoms arranged differently in space

• There are two types of stereoisomerism

  • Geometrical (E / Z)

  • Optical

• A carbon atom that has four different atoms or groups of atoms attached to it is called a chiral carbon or chiral centre

  • Chira comes from a Greek word meaning hand, so we talk about these molecules having a handedness

• Compounds with a chiral centre (chiral molecules) exist as two optical isomers which are also known as enantiomers

• The enantiomers are non-superimposable mirror images of each other just like your left and right hand

A molecule has a chiral centre when the carbon atom is bonded to four different atoms or group of atoms; this gives rises to enantiomers