Isomerism

• Define isomer

  Molecules with the same molecular formula but different structures
• Define structural isomers

  Molecules with the same molecular formula but different arrangement of covalent bonds
• Define positional isomerism

  Molecules with the same molecular formula but the functional group is on different positions in the molecule
• Define chain isomerism

  Molecules with the same molecular formula but different arrangement of carbon atoms
• Define functional isomerism

  Molecules with the same molecular formula but different functional groups
• How do we distinguish between isomers?

  Isomers differ in boiling points
• Define a stereoisomer

  Molecules with the same molecular formula and the same arrangement of covalent bonds but with different spatial orientations of the group
• What are E-Z isomers?

  Stereoisomers with different spatial orientations around the C=C. It is caused by restricted rotation around the bond and arises when the C atom on both sides are attached to different groups
• When does E isomerism occur?

  When the same groups are opposite the double bond
• When does Z isomerism occur?

  When the same groups are on the same side of the double bond
• What are the rules used to decide if an isomer is E or Z?

  Cahn-Ingold-Prelog rules
• Describe the Cahn-Ingold-Prelog rules

  -Label the carbons on the double bond as 1 and 2

  -Calculate the atomic number of each element directly bonded to the double bond

  -The atom with the highest atomic number has the highest priority

  -Look at the positions of the two high priority atoms to identify E/Z isomerism