6.2.8 - Stereoisomerism

• what is stereoisomerism?

  when molecules with the same molecular and structural formula have different spacial arrangement of atoms due to lack of rotation around the double bond
• types of stereoisomerism

  geometric

  optical
• ways of naming geometric isomerism

  E/Z isomerism

  cis-trans isomerism
• what is E/Z isomerism?

  where there is restricted rotation about a bond and different groups are attached to carbon atoms at each end of the bond
• what's the Z-isomer?

  same groups positioned across the double bond
• what's the E-isomer?

  same groups above or below the double bond
• how to determine the E/Z isomer if all groups attached to the carbon atoms are different

  use CIP rules: atom with highest atomic number on either carbon atom in the double bond has priority
• what is cis-trans isomerism?

  a type of E/Z isomerism where carbon atoms have at least one group in common
• what's the cis isomer?

  same groups on the same side of the double bond
• what's the trans isomer?

  same groups on opposite sides of the double bond