What is the difference between structural isomers and stereoisomers?

The distinction between structural isomers and stereoisomers primarily lies in their structural organization and how that affects their properties.

Structural isomers share the same molecular formula, meaning they contain the same number of each type of atom, but differ in the connectivity of these atoms. This connectivity can manifest in various ways, such as branching, functional groups, or the sequence of atoms, leading to different chemical compounds with distinct properties. For example, butane and isobutane both contain four carbon atoms and ten hydrogen atoms, but their arrangements are different, thus categorizing them as structural isomers.

In contrast, stereoisomers also have the same molecular formula and connectivity of atoms, but they differ in the three-dimensional arrangement of their atoms in space. This spatial arrangement can result from rotations around single bonds or the presence of double bonds that create fixed geometries.

Therefore, stating that structural isomers have the same molecular formula but different connectivity accurately captures the essence of what differentiates them from other types of isomers, specifically stereoisomers.