Isomers (Constitutional)

Organic molecules that have the same molecular formula (e.g., same number of carbons, hydrogens, etc.) but which are connected differently are referred to as Constitutional Isomers.  Examples are for butane and isobutane, or for pentane, isopentane, and neopentane. Sometimes referred to as Structural Isomers, Constitutional Isomers have the same mass, but different physical and chemical properties.