Functional Group Isomerism
Structural isomerism in which compounds of the same formula contain entirely different functional groups.
Unit
Dimensionless
In depth
Because the functional group determines chemistry, these isomers behave as completely different substances with widely separated boiling points and reactivities. They belong to different homologous series despite sharing a molecular formula.
Examples in the real world
Ethanol and dimethyl ether (C₂H₆O); propanal and propanone (C₃H₆O); ethanoic acid and methyl methanoate.