Stereoisomerism

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Stereoisomerism
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Cis-trans isomerism

• Geometric isomerism (also known as cis-trans
  isomerism) is a form of stereoisomerism

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• cis isomer "on this side"
• trans isomer "across

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• Try naming these molecules

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The effect of geometric isomerism on physical
properties

• cis and trans isomers of 1,2-dichloroethene.
• In each case, the higher melting or boiling point
  is shown in red.

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• BP cis isomer is a polar molecule whereas the
  trans isomer is non-polar, therefore cis has
  dipole-dipole interactions as well as the van der
  Waals forces that exist in both molecules
• MP for the intermolecular forces to work well,
  the molecules must be able to pack together
  efficiently in the solid (trans pack better)

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The effect of geometric isomerism on chemical
properties

• cis- and trans-but-2-ene-1,4-dioic acid react
  differently when heated.