isooctane

chemical compound

Also known as: 2,2,4-trimethylpentane

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June 29, 2026

Quick Summary

Isooctane is a branched-chain octane, a flammable liquid used to determine the octane number of fuels. The octane number measures a fuel's resistance to knocking in an internal-combustion engine. This is determined by comparing the fuel's knock intensity to blends of iso-octane (which resists knocking) and heptane (which knocks easily).12

In petroleum refining, isooctane is a key component produced through a process called alkylation. Alkylation combines light hydrocarbons like olefins and isoparaffins to create high-octane gasoline components. Isooctane is particularly valued for its excellent antiknock characteristics.3

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hydrocarbon
Chemical reactions
…material in the preparation of 2,2,4-trimethylpentane (isooctane), which is a component of high-octane gasoline.
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…material in the preparation of 2,2,4-trimethylpentane (isooctane), which is a component of high-octane gasoline.
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hydrocarbon
Polymerization
…suitable for subsequent conversion to 2,2,4-trimethylpentane (isooctane).
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…suitable for subsequent conversion to 2,2,4-trimethylpentane (isooctane).
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octane number
…blends of two reference fuels: iso-octane, which resists knocking, and heptane, which knocks readily. The octane number is the percentage by volume of iso-octane in the iso-octane–heptane mixture that matches the fuel being tested in a standard test engine. See also knocking.
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…blends of two reference fuels: iso-octane, which resists knocking, and heptane, which knocks readily. The octane number is the percentage by volume of iso-octane in the iso-octane–heptane mixture that matches the fuel being tested in a standard test engine. See also knocking.
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