Octane

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.

Octane has 18 isomers :
 * Octane (n-octane)
 * 2-Methylheptane
 * 3-Methylheptane
 * 4-Methylheptane
 * 3-Ethylhexane
 * 2,2-Dimethylhexane
 * 2,3-Dimethylhexane
 * 2,4-Dimethylhexane
 * 2,5-Dimethylhexane
 * 3,3-Dimethylhexane
 * 3,4-Dimethylhexane
 * 2-Methyl-3-ethylpentane
 * 3-Methyl-3-ethylpentane
 * 2,2,3-Trimethylpentane
 * 2,2,4-Trimethylpentane (isooctane)
 * 2,3,3-Trimethylpentane
 * 2,3,4-Trimethylpentane
 * 2,2,3,3-Tetramethylbutane