Octane

Octane is a hydrycarbon and an alkane with the chemical formula C8H18, and is a primary factor of burning gasoline. It has many structural isomers that differ by the amount and location of branching in the carbon chain. Octane is highly flammable.

Use of the term 'gasoline' [[image:Grey_Octane1.jpg height="89" align="left"]]
Octane is short for the phrase 'octane rating' particularly meaning 'high octane' The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine which can damage an engine. The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio.

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Octane rating is a standard measure of the performance of a motor or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating. In broad terms, fuels with a higher octane rating are used in high-compression engines that generally have higher performance. Fuels with low numbers are for diesel engines which could lead to engine knocking.

Metaphorical use
Octane became well known in American popular culture in the mid- and late-sixties, when [|gasoline] companies boasted of "high octane" levels in their gasoline in advertisements.

These commercials disappeared by the time of the [|1973 Oil Crisis], which spared gasoline companies the need to compete via advertising. "Octane" was rarely cited in non-technical contexts over the next two decades.

The compound adjective "high-octane" was apparently first used in its figurative sense (i.e., without reference to gasoline) in a book review of [|Michael Crichton] 's novel // [|Jurassic Park] // (1990), which appeared in the newspaper New York // [|Newsday] //.[// [|citation needed] //] The review by Gregory Feeley called the novel "intellectually provocative, high-octane entertainment", and was quoted the following year in the front matter of the novel's paperback edition, which sold more than 15 million copies in the United States. By the mid-nineties, the phrase was commonly being used as an intensifier and has apparently found a place in modern English vernacular.

Isomers
Octane has 18 structural isomers (24 including [|stereoisomers] ):


 * Octane (//n//-octane)
 * [|2-Methylheptane]
 * [|3-Methylheptane] (2 [|enantiomers] )
 * [|4-Methylheptane]
 * [|3-Ethylhexane]
 * [|2,2-Dimethylhexane]
 * [|2,3-Dimethylhexane] (2 enantiomers)
 * [|2,4-Dimethylhexane] (2 enantiomers)
 * [|2,5-Dimethylhexane]
 * [|3,3-Dimethylhexane]
 * [|3,4-Dimethylhexane] (2 enantiomers + 1 [|meso compound] )
 * [|3-Ethyl-2-methylpentane]
 * [|3-Ethyl-3-methylpentane]
 * [|2,2,3-Trimethylpentane] (2 enantiomers)
 * [|2,2,4-Trimethylpentane] (isooctane)
 * [|2,3,3-Trimethylpentane]
 * [|2,3,4-Trimethylpentane]
 * [|2,2,3,3-Tetramethylbutane]
 * ~ Properties ||
 * [|Molecular formula] || C8H18 ||
 * [|Molar mass] || 114.23 g mol−1 ||
 * Appearance || Colorless, transparent liquid ||
 * [|Odor] || Petrolic ||
 * [|Density] || 703 mg mL−1 ||
 * [|Melting point] || -57--57 °C, 216.0-216.6 K, -71--70 °F ||
 * [|Boiling point] || 125-126 °C, 398.2-399.2 K, 257-259 °F ||
 * [|Solubility] in [|water] || 7 mg L−1 (at 20 C°) ||
 * [|log P] || 4.783 ||
 * [|Vapor pressure] || 1.47 kPa (at 20.0 °C) ||
 * [|kH] || 29 nmol Pa−1 kg−1 ||
 * [|Refractive index] (//n//D) || 1.398 ||
 * [|Viscosity] || 542 μPa s (at 20 °C) ||