What is structural isomerism?

Structural isomerism occurs when compounds share the same molecular formula, meaning they contain the same number of each type of atom, but differ in how these atoms are arranged or connected to one another, resulting in different structural representations. This variation in connectivity leads to distinct compounds that exhibit different properties.

For instance, consider butane (C4H10) and isobutane (also C4H10). They are structural isomers because, despite having the same molecular formula, the arrangement of carbon atoms differs, which affects their boiling points and other physical properties.

The concept captures the idea that even a slight change in the arrangement of atoms can result in significantly different compounds, which is central to understanding structure-activity relationships in chemistry.