The structural formulas of the compounds n-butane and isobutane are shown below. (c) Which formulas—empirical, molecular, or structural—allow you determine these are different compounds?

Key Concepts

Structural Isomerism

Structural isomerism occurs when compounds have the same molecular formula but different structural formulas. In the case of n-pentane and isopentane, both have the molecular formula C5H12, yet their structural arrangements differ, leading to distinct physical and chemical properties. Understanding this concept is crucial for identifying how compounds can be classified as different despite having the same number of atoms.

Empirical vs. Molecular vs. Structural Formulas

Empirical formulas represent the simplest whole-number ratio of elements in a compound, while molecular formulas indicate the actual number of each type of atom present. Structural formulas provide a visual representation of how atoms are connected. To determine that n-pentane and isopentane are different compounds, one must analyze their structural formulas, as they reveal the distinct arrangements of atoms that define each compound.

Chemical Properties and Reactivity

The chemical properties and reactivity of compounds can vary significantly based on their structure. Isomers, such as n-pentane and isopentane, may exhibit different boiling points, melting points, and reactivity due to their unique arrangements of atoms. Recognizing these differences is essential for understanding how structural variations influence the behavior of chemical substances.