Pentane (C₅H₁₂) is an alkane with the molecular formula CH₃(CH₂)₃CH₃. Structural isomers are compounds with the same molecular formula but different structural arrangements of atoms. For pentane, there are three main structural isomers:

1. n-Pentane (Normal Pentane):

» CH₃CH₂CH₂CH₂CH₃

2. Isopentane (Methylbutane):

» CH₃CH(CH₃)CH₂CH₃

3. Neopentane (Dimethylpropane):

» (CH₃)₃CCH₃
These are the only structural isomers of pentane because, for a linear chain of five carbon atoms, there is only one way to arrange them (n-pentane). Adding branches to the chain (isopentane or neopentane) creates the other structural isomers.