IB ChemistryStructure 33.23.2.6
HL

Structural Isomers

Same molecular formula, different connectivities.

Types of Structural Isomerism

1. Chain Isomerism

Carbon skeleton arranged differently (branching).

Pentane
vs
2-methylbutane

2. Positional Isomerism

Same functional group, different position on chain.

Pentan-1-ol
vs
Pentan-2-ol

3. Functional Group

Atoms rearranged to form a different compound family.

Ethanol
vs
Methoxymethane

Common Functional Group Isomer Pairs

  • Alcohols ↔ Ethers (e.g., \(C_2H_6O\))
  • Aldehydes ↔ Ketones (e.g., \(C_3H_6O\))
  • Carboxylic Acids ↔ Esters (e.g., \(C_2H_4O_2\))
  • Alkenes ↔ Cycloalkanes (e.g., \(C_3H_6\))