How do molecular formulas differ from structural formulas for organic compounds?

Molecular formulas and structural formulas serve different purposes in representing organic compounds:

• Molecular Formulas: These specify only the number and type of each atom present in a molecule. For example, the molecular formula for butane is ${\text{C}}_4{\text{H}}_{10}$, which indicates it contains four carbon atoms and ten hydrogen atoms. However, this formula does not reveal how those atoms are connected or arranged.12

• Structural Formulas: These identify the specific location of chemical bonds between atoms. By using lines to represent covalent bonds, they show the order of attachment and the bonding arrangement. This is essential for organic chemistry because different compounds can share the same molecular formula but possess different structures, a phenomenon known as isomerism. For instance, butane can exist as a linear chain or a branched structure; while both share the formula ${\text{C}}_4{\text{H}}_{10}$, their unique structural formulas distinguish them as different compounds with distinct properties.123

In summary, while a molecular formula provides a simple inventory of atoms, a structural formula provides the necessary detail to understand the molecule's connectivity and architecture.2