Octane Information

Octane is a hydrocarbon and an alkane with the chemical formula C₈H₁₈, and the condensed structural formula CH₃(CH₂)₆CH₃. Octane has many structural isomers that differ by the amount and location of branching in the carbon chain. One of these isomers, 2,2,4-trimethylpentane (isooctane) is used as one of the standard values in the octane rating scale.

As with all low-molecular weight hydrocarbons, octane and its isomers are very flammable. It and its isomers are components of gasoline (petrol).

Use of the term in gasoline

"Octane" is colloquially used as a short form of "octane rating" (named for the ability of octane's branched-chain isomers, especially isooctane, to reduce engine knock), particularly in the expression "high octane". However, components of gasoline other than isomers of octane can also contribute to a high octane rating, while some isomers of octane can lower it, and n-octane itself has a negative octane rating.^[2]

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. 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

References

1. ^ "octane - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 16 Sepember 2004. Identification and Related Records. http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=356&loc=ec_rcs. Retrieved 6 January 2012.
2. ^ eejit's guides – Octane ratings explained

External links

• International Chemical Safety Card 0933
• NIOSH Pocket Guide to Chemical Hazards 0470
• Phytochemical database entry

Categories:

• Alkanes

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