# Why should the properties of structural isomers differ?

${\text{H"_3"CCH"_2"CH"_2"CH"_2"CH}}_{3}$, $\text{n-pentane}$, ${\text{H"_3"CCH(CH"_3")CH"_2"CH}}_{3}$, $\text{isopentane}$, ${\text{C(CH"_3")}}_{4}$, $\text{neopentane}$.
These have respective boiling points of $36$ ""^@C, $30$ ""^@C, and $9.5$ ""^@C; this is a fairly wide boiling point range for ${C}_{5} {H}_{12}$. Clearly, the more branched the isomer, the less opportunity there are for chain-chain interactions, and the less intermolecular interaction, the lower the boiling point. And thus even for a short-chain hydrocarbon, isomerism affects volatility.