What is the IUPAC name of the compound with the molecular formula C4H8?

The molecular formula C4H8 corresponds to an alkene, which is a type of hydrocarbon that contains a carbon-carbon double bond. The prefix "but-" indicates that the compound has four carbon atoms. Since there is a double bond present, the compound is categorized as an alkene, and the appropriate nomenclature uses the suffix "-ene" rather than "-ane," which would be used for single-bonded compounds (alkanes), or "-yne," which would be used for triple-bonded compounds (alkynes).

The correct name for the compound is butene, as it reflects both the number of carbon atoms (four) and the presence of a double bond. Therefore, butene is the appropriate IUPAC name for a compound with the molecular formula C4H8, which can exist in different structural isomers, such as 1-butene or 2-butene, but all of these would fall under the general name butene. This distinguishes it clearly from butane, which would not have any double bonds, and does not relate to pentene, which contains five carbon atoms.