224Trimethylpentane

2,2,4-Trimethylpentane, commonly known as iso-octane or isooctane, is a branched alkane with the formula C8H18. It is one of the eight structural isomers of octane and is valued for its high resistance to knocking in internal combustion engines. Its name reflects its structure: a pentane backbone with two methyl groups at carbon 2 and one methyl group at carbon 4.

In petroleum refining, iso-octane is produced by rearranging straight-chain alkanes through processes such as catalytic reforming and hydroisomerization. It is a key component of gasoline blends and contributes to higher octane ratings.

Properties of iso-octane include being a colorless liquid at room temperature that is largely insoluble in water and miscible with other hydrocarbons. It is highly flammable and, like other light hydrocarbons, upon vaporization forms potentially explosive mixtures with air. Typical physical data place its boiling point around 99°C and its density near 0.69 g/mL at room temperature, though these values can vary with precise composition and conditions.

Uses and significance: Iso-octane is used as a high-octane blending component to improve gasoline performance. It is also the reference fuel for the 100 octane rating on the Research Octane Number scale, meaning a fuel with an RON of 100 closely matches its anti-knock characteristics.

See also: Octane rating, Isomers of octane, Gasoline blending.