Noun
Any one of several isometric hydrocarbons, C7H16, of the paraffin series (nine are possible, four are known); -- so called because the molecule has seven carbon atoms. Specifically, a colorless liquid, found as a constituent of petroleum, in the tar oil of cannel coal, etc.
Source: Webster's dictionaryThis propensity to premature ignition is measured by the octane rating of the fuel, where 2,2,4-trimethylpentane (isooctane) has an arbitrary value of 100, and heptane has a value of zero. Source: Internet
Pentane, hexane, heptane, and octane are classed as dangerous for the environment and harmful. Source: Internet