octane

n. unit of quality measurement in automobile gasoline; hydrocarbon with eight carbon atoms

For the gasoline rating system, see Octane rating, or for other uses, see Octane (disambiguation). Octane is an alkane with the chemical formula CH3(CH2)6CH3. It has 18 isomers.One of the isomers, 2,2,4-trimethylpentane or isooctane, is of major importance, as it has been selected as the 100 point on the octane rating scale, with n-heptane as the zero point. Octane ratings are ratings used to represent the anti-knock performance of petroleum-based fuels (octane is less likely to prematurely combust under pressure than heptane), given as the percentage of 2,2,4-trimethylpentane in an 2,2,4-trimethylpentane / n-heptane mixture that would have the same performance. It is an important constituent of gasoline.
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Noun
1. any isomeric saturated hydrocarbon found in petroleum and used as a fuel and solvent
(hypernym) hydrocarbon

n. octane, unit of quality measurement in automobile gasoline; hydrocarbon with eight carbon atoms

(n.)
Any one of a group of metametric hydrocarcons (C8H18) of the methane series. The most important is a colorless, volatile, inflammable liquid, found in petroleum, and a constituent of benzene or ligroin.