Isomerism

Question 1

Isomers

define and two types

1.3 Isomerism

Answer 1

Have the same molecular formula but the atoms are arranged differently

There are 2 basic types:
* Structural isomerism
* Stereoisomerism

Question 2

Structural isomerism – 3 sub-divisions

1.3 Isomerism

Answer 2

• Positional isomerism - The functional group is attached to the main
  chain at different points eg C3H7Cl
• Functional group isomerism - There are different functional groups eg
  C2H6O
• Chain isomerism -The hydrocarbon chain can be arranged differently. These are called chain-branching isomers eg C4H9OH. Doesn’t have to have a functional group

Question 3

Stereoisomers

1.3 Isomerism

Answer 3

• These have a different spatial arrangement. A type of stereoisomerism is E-Z isomerism, where limited rotation around a double carbon bond.
• The E isomer (german for entgegen meaning apart) has these groups apart.
• The Z isomer (german for zusammen meaning together) has these groups together on the same side of the double bond.

Question 4

Cahn-Ingold-Prelog (CIP) Priority Rules

1.3 Isomerism

Answer 4

• There is a priority of different groups in molecules that can display E-Z isomerism.
• The atom or group on each side of the double bond with the higher Ar or Mr is given the higher priority.
• These groups are used to determine if it is the E or Z isomer.