Optical Isomerism

• • optical isomerism is a form of stereoisomerism
  • same structural formula, different arrangement of atoms in space
• • optical isomers are mirror images of each other and have a chiral carbon atom
  • a chiral carbon is a carbon with 4 different groups attached to it
• • optical isomers can be arranged in two different ways to create two different molecules - these are called enantiomers
  • enantiomers are mirror images of each other and are non-superimposable
• • optically active isomers rotate plane-polarised light
  • one enantiomer rotates the light clockwise and the other rotates it anti-clockwise
• plane polarised light only oscillates in one direction
• a racemic mixture is when there is an equal amount of each enantiomer
• • racemates don't rotate plane-polarised light
  • the two enantiomers rotate the light in opposite directions and cancel each other out
• • it is difficult to adapt a reaction to only produce one enantiomer
  • it is also expensive
• • molecules containing planar groups such as C=C and C=O can make racemic products
  • the nucleophile has an equal chance of attacking the planar group from above or below, forming a 50/50 mix of the 2 different enantiomers