Octane

Octane

Octane

Hydrocarbon compound with the formula C8H18

Not to be confused with octene or octyne.
For the gasoline rating system, see Octane rating. For other uses, see Octane (disambiguation).

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 location of branching in the carbon chain. One of these isomers, 2,2,4-trimethylpentane (commonly called iso-octane), is used as one of the standard values in the octane rating scale.

Quick Facts Names, Identifiers ...

Octane is a component of gasoline and petroleum. Under standard temperature and pressure, octane is an odorless, colorless liquid. Like other short-chained alkanes with a low molecular weight, it is volatile, flammable, and toxic. For examples, as a neurotoxin with narcotic effects, n-octane is almost twice times as toxic as n-heptane.[5]

Isomers

N-octane has 23 constitutional isomers. 8 of these isomers have one stereocenter; 3 of them have two stereocenters.

(3S,4S)-3,4-Dimethylhexane (top left) and (3R,4R)-3,4-Dimethylhexane (top right) are non-superimposable mirror images, so they are chiral enantiomers. (meso)-3,4-Dimethylhexane (bottom) has a superimposable mirror image, so it is an achiral meso compound.

Achiral Isomers:

Chiral Isomers:

Production and Use

In petrochemistry, octanes are not typically differentiated or purified as specific compounds. Octanes are components of particular boiling fractions.[6]

A common route to such fractions is the alkylation reaction between iso-butane and 1-butene, which forms iso-octane.[7]

Octane is commonly used as a solvent in paints and adhesives.

N-octane is the octane isomer that has the longest carbon skeleton. Unlike its constitutional isomers, it has a very low knock resistance.
The octane isomer, iso-octane, is used as one of the standards for octane ratings. It has a rating of 100 by definition.
The octane isomer 2,3,3-Trimethylpentane has an octane rating exceeding 100.

References

  1. [1]
    "octane - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 16 September 2004. Identification and Related Records. Retrieved 6 January 2012.
  2. [2]
    NIOSH Pocket Guide to Chemical Hazards. "#0470". National Institute for Occupational Safety and Health (NIOSH).
  3. [3]
    Dymond, J. H.; Oye, H. A. (1994). "Viscosity of Selected Liquid n-Alkanes". Journal of Physical and Chemical Reference Data. 23 (1): 41–53. Bibcode:1994JPCRD..23...41D. doi:10.1063/1.555943. ISSN 0047-2689.
  4. [4]
    "Octane". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  5. [5]
    "1988 OSHA PEL Project - Octane | NIOSH | CDC". www.cdc.gov. 2020-02-27. Retrieved 2024-04-19.
  6. [6]
    "Fractionation". www.appliedcontrol.com. Retrieved 2024-04-19.
  7. [7]
    Ross, Julian (January 1986). "Ullmann's Encyclopedia of industrial chemistry". Applied Catalysis. 27 (2): 403–404. doi:10.1016/s0166-9834(00)82943-7. ISSN 0166-9834.
Share this article:

This article uses material from the Wikipedia article Octane, and is written by contributors. Text is available under a CC BY-SA 4.0 International License; additional terms may apply. Images, videos and audio are available under their respective licenses.