Isomerism: A Quick Revision

Isomerism is a phenomenon where two or more compounds have the same molecular formula but different properties due to different arrangements of atoms within the molecule.  

Types of Isomerism

Structural Isomerism

• Chain Isomerism: Different branching patterns of the carbon chain.
  • Example: Butane and 2-methylpropane  
   
• Position Isomerism: Different positions of functional groups on the carbon chain.
  • Example: 1-chloropropane and 2-chloropropane  
   
• Functional Group Isomerism: Different functional groups with the same molecular formula.
  • Example: Ethanol and dimethyl ether  
    

Stereoisomerism

• Geometric Isomerism (Cis-Trans Isomerism): Different spatial arrangement of atoms around a double bond or a ring structure.
  • Example: cis- and trans-butene  
   
• Optical Isomerism: Compounds that are non-superimposable mirror images of each other.
  • Example: D- and L-glucose  
    

Key Points

• Isomers have the same molecular formula but different structures and properties.  
• Structural isomers differ in the arrangement of atoms within the molecule.  
• Stereoisomers have the same arrangement of atoms but differ in their spatial orientation.
• Geometric isomers have different spatial arrangements around a double bond or ring.  
• Optical isomers are non-superimposable mirror images.  

Remember:

• Practice drawing and identifying isomers.
• Understand the differences between structural and stereoisomers.
• Be familiar with the different types of structural and stereoisomerism.
• Use the CIP (Cahn-Ingold-Prelog) rules for determining R/S configurations in optical isomers.