Also found in: Dictionary, Wikipedia.
2,2,4-trimethylpentane, the saturated aliphatic hydrocarbon C(CH3)3—CCH2—CH(CH3)2.
Isooctane is a transparent colorless liquid with a gasoline odor. Melting point, - 107.38°C; boiling point, 99.24°C; density, 0.69192 g/cm3 (20°C); nD20, 1.39145; heat of combustion, 5.463 megajoules per mole, or 1,305.29 kilocalories per mole (25°C; p = const); heat of vaporization, 307.63 joules per g, or 73.50 calories per g (25°C). Isooctane is insoluble in water but soluble in ordinary organic solvents. It forms azeotropes (for example, with benzene, methanol, and ethanol). The knock rating of isooctane is assigned an octane number of 100.
Straight-run gasolines contain small amounts of isooctane along with other octane isomers. Industrially, isooctane is made by hydrogenating diisobutylene over a catalyst (for example, copper-chromium) or by alkylating isobutane with isobutylene in the presence of concentrated H2S04, A1C13, BF3, or other catalysts. Isooctane is used (as an additive) in making aviation gasolines, which must have excellent antiknock properties.