Optical isomerism is a form of stereoisomerism and occurs as a result of chirality in molecules, limited to molecules with a single chiral centre.

An asymmetric carbon atom is chiral and gives rise to optical isomers (enantiomers), which exist as non super-imposable mirror images and differ in their effect on plane polarised light.

A mixture of equal amounts of enantiomers is called a racemic mixture (racemate).

Students should be able to:
- draw the structural formulas and displayed formulas of enantiomers
- understand how racemic mixtures (racemates) are formed and why they are optically inactive.