2,2,4-Trimethylpentane

2,2,4-Trimethylpentane, also known as isooctane or iso-octane, is an <a href="/facts/Organic_compound/gqCNaN45">organic compound</a> with the formula (CH3)3CCH2CH(CH3)2. It is one of several <a href="/facts/Isomer/PXlvDVdg">isomers</a> of <a href="/facts/Octane/3E91j6Fe">octane</a> (C8H18). This particular isomer is the standard 100 point on the <a href="/facts/Octane_rating/LqkAlYbq">octane rating</a> scale (the zero point is <a href="/facts/Heptane/jP4XjrBe">n-heptane</a>). It is an important component of <a href="/facts/Gasoline/lcnxq5BS">gasoline</a>, frequently used in relatively large proportions (around 10%) to increase the <a href="/facts/Engine_knocking/k9rhaaYD">knock</a> resistance of fuel.
Strictly speaking, if the standard meaning of ‘iso’ is followed, the name isooctane should be reserved for the isomer <a href="/facts/2-methylheptane/SVxe3Mdn">2-methylheptane</a>. However, 2,2,4-trimethylpentane is by far the most important isomer of octane and historically it has been assigned this name.

2,2,4-Trimethylpentane open-in-new

2,2,4-Trimethylpentane