Isomerism

• Isomers are molecules that have the same molecular formula but have a different arrangement.
• There are 2 main branches of isomerism:

  • Structural
  • Stereoisomerism (or geometric)
• Structural isomers can have:

  • The same functional groups attached to the main chain at different points (Positional isomerism)
  • Different functional groups (Functional group isomerism)
  • Different arrangement of the carbon chain e.g. branching (Chain isomerism)
• Positional isomerism

  • When the functional group is attached to the main chain at different points
• Functional group isomerism

  • When there are different functional groups attached
• Chain isomerism

  • When the hydrocarbon chain is arranged differently
• Structural isomers are also known as chain-branching isomers.
• Stereoisomerism

  • When they have the same structural formula but the arrangement of bonds in space are different
• Stereoisomerism

  • E-Z isomerism
  • Optical isomerism
• E-Z isomers are different and not easily converted, no rotation around the double bond