What defines functional isomers?

Functional isomers are defined by the existence of compounds that differ in their functional groups. This means that these compounds can have the same molecular formula but exhibit different chemical properties due to the distinct functional groups present. For example, an aldehyde and a ketone both contain the same number of carbons, hydrogens, and oxygens (for instance, both can have the formula C3H6O) but differ in the arrangement and type of their functional groups.

This difference significantly influences their reactivity, boiling points, solubility, and overall chemical behavior. Understanding this concept is critical as it highlights how the same atoms can be rearranged to create compounds with different characteristics based solely on the presence of different functional groups.