What is the IUPAC name for C8H18?

The compound with the molecular formula C8H18 is an alkane, which is a saturated hydrocarbon consisting solely of carbon and hydrogen atoms with single bonds. To determine its IUPAC name, we must identify the longest continuous chain of carbon atoms in the molecule.

In this case, the longest chain consists of eight carbon atoms, which corresponds to the prefix "oct-" in IUPAC nomenclature. Since it is solely composed of single bonds and follows the general formula for alkanes (CnH2n+2, where n is the number of carbon atoms), this molecule is octane.

Octane is commonly used in fuels and is well-known for its role in determining gasoline stability in engines. The other names listed correspond to hydrocarbons with different numbers of carbon atoms: decane has 10 carbon atoms, pentane has 5, and heptane has 7. Thus, octane is the correct and specific name for C8H18, reflecting its structure accurately in line with IUPAC conventions.