Octane, << OK tayn, >> is any of 18 chemical compounds that consist of 8 carbon atoms and 18 hydrogen atoms. Some octanes are among the main ingredients of gasoline. An octane called isooctane is used in a test mixture to determine how well a gasoline resists knocking (see Octane number ). Gasolines that have a high octane number can prevent engine knock better than those with a lower octane number.
Octanes belong to a group of chemicals called hydrocarbons (see Hydrocarbon ). All octanes are colorless liquids, all are highly flammable, and all have the same molecular formula. However, they have different molecular structures and therefore different chemical and physical properties. For example, normal octane, also called n-octane, boils at 258.2 °F. (125.7 °C). Isooctane, which has the same chemical formula but a differently shaped molecule, boils at 210.6 °F. (99.2 °C).
