Isomers are compounds that have the same molecular formula—meaning they contain the same number and types of atoms—but differ in the arrangement of those atoms. This difference in structure leads to distinct physical and chemical properties.
There are two main types of isomers:
- Structural (or constitutional) isomers – Atoms are connected in different orders.
- Example: Butane (C₄H₁₀) and isobutane have different carbon chain structures.
- Stereoisomers – Atoms are connected in the same order but differ in the spatial arrangement. These include:
- Geometric (cis-trans) isomers – Different positions around a double bond or ring.
- Enantiomers – Mirror-image isomers (chiral compounds).
- Diastereomers – Stereoisomers that are not mirror images.
Isomerism is crucial in organic chemistry, biochemistry, and pharmaceuticals, as different isomers of the same compound can have drastically different biological effects.