Wikipedia

Octane

(Redirected fromN-octane)
Not to be confused withocteneoroctyne.
For the gasoline rating system, seeOctane rating.For other uses, seeOctane (disambiguation).

Octaneis ahydrocarbonand analkanewith thechemical formulaC8H18,and the condensed structural formula CH3(CH2)6CH3.Octane has manystructural isomersthat differ by the location of branching in thecarbon chain.One of these isomers,2,2,4-trimethylpentane(commonly called iso-octane), is used as one of the standard values in theoctane ratingscale.

Octane
Skeletal formula of octane
Skeletal formula of octane with all implicit carbons shown, and all explicit hydrogens added
Ball-and-stick model of octane
Space-filling model of octane
Names
Systematic IUPAC name
Octane[1]
Other names
n-Octane
Identifiers
3D model (JSmol)
3DMet
1696875
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.003.539Edit this at Wikidata
EC Number
  • 203-892-1
82412
KEGG
MeSH octane
RTECS number
  • RG8400000
UNII
UN number 1262
  • InChI=1S/C8H18/c1-3-5-7-8-6-4-2/h3-8H2,1-2H3checkY
    Key: TVMXDCGIABBOFY-UHFFFAOYSA-NcheckY
  • CCCCCCCC
Properties
CH3(CH2)6CH3
Molar mass 114.232g·mol−1
Appearance Colourless liquid
Odor Gasoline-like[2]
Density 0.703 g/cm3
Melting point −57.1 to −56.6 °C; −70.9 to −69.8 °F; 216.0 to 216.6 K
Boiling point 125.1 to 126.1 °C; 257.1 to 258.9 °F; 398.2 to 399.2 K
0.007 mg/dm3(at 20 °C)
logP 4.783
Vapor pressure 1.47 kPa (at 20.0 °C)
29 nmol/(Pa·kg)
Conjugate acid Octonium
−96.63·10−6cm3/mol
1.398
Viscosity
  • 0.509 mPa·s (25 °C)[3]
  • 0.542 mPa·s (20 °C)
Thermochemistry
255.68 J/(K·mol)
361.20 J/(K·mol)
−252.1 to −248.5 kJ/mol
−5.53 to −5.33 MJ/mol
Hazards
GHSlabelling:
GHS02: FlammableGHS07: Exclamation markGHS08: Health hazardGHS09: Environmental hazard
Danger
H225,H304,H315,H336,H410
P210,P261,P273,P301+P310,P331
NFPA 704(fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
3
0
Flash point 13.0 °C (55.4 °F; 286.1 K)
220.0 °C (428.0 °F; 493.1 K)
Explosive limits 0.96 – 6.5%
Lethal doseor concentration (LD, LC):
428 mg/kg (mouse, intravenous)[4]
NIOSH(US health exposure limits):
PEL(Permissible)
 TWA 500 ppm (2350 mg/m3)[2]
REL(Recommended)
 TWA 75 ppm (350 mg/m3) C 385 ppm (1800 mg/m3) [15-minute][2]
IDLH(Immediate danger)
 1000 ppm[2]
Related compounds
Related alkanes
Except where otherwise noted, data are given for materials in theirstandard state(at 25 °C [77 °F], 100 kPa).

Octane is a component ofgasolineand petroleum. Understandard temperature and pressure,octane is an odorless, colorless liquid. Like other short-chained alkanes with a low molecular weight, it isvolatile,flammable, and toxic. Octane is 1.2 to 2 times more toxic thanHeptane.[5]

Isomers

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N-octane has 23constitutional isomers.8 of these isomers have onestereocenter;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 chiralenantiomers.(meso)-3,4-Dimethylhexane(bottom) has a superimposable mirror image, so it is an achiralmeso compound.

Achiral Isomers:

Chiral Isomers:

Production and Use

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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 thealkylation reactionbetween iso-butane and 1-butene, which forms iso-octane.[7]

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

N-octaneis 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 isomer2,3,3-Trimethylpentanehas an octane rating exceeding 100.

References

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  1. ^"octane - Compound Summary".PubChem Compound.USA: National Center for Biotechnology Information. 16 September 2004. Identification and Related Records.Retrieved6 January2012.
  2. ^abcdNIOSH Pocket Guide to Chemical Hazards."#0470".National Institute for Occupational Safety and Health(NIOSH).
  3. ^Dymond, J. H.; Oye, H. A. (1994). "Viscosity of Selected Liquidn-Alkanes ".Journal of Physical and Chemical Reference Data.23(1): 41–53.Bibcode:1994JPCRD..23...41D.doi:10.1063/1.555943.ISSN0047-2689.
  4. ^"Octane".Immediately Dangerous to Life or Health Concentrations (IDLH).National Institute for Occupational Safety and Health(NIOSH).
  5. ^"1988 OSHA PEL Project - Octane | NIOSH | CDC".www.cdc.gov.2020-02-27.Retrieved2024-04-19.
  6. ^"Fractionation".www.appliedcontrol.com.Retrieved2024-04-19.
  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.ISSN0166-9834.
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