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octane (C8H18)




A liquid alkane with 18 isomers that are constituents of gasoline. Normal octane occurs in petroleum; the branched isomers, which have high antiknock values, are made by alkylation.

The octane number of a gasoline is the percentage of iso-octane (2,2,4-trimethylpentane) in the mixture of iso-octane with n-heptane, which, in standard tests, knocks to the same degree as the gasoline. Antiknock additives and modern refining techniques can raise the octane number above 100.


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