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Octane

From Quire, the open reference·Hydrocarbon compound with the formula C8H18·1 min read
Octane
Octane
Image: source and license
Names
Systematic IUPAC name
Octane[1]
Other names
n-Octane
Identifiers
CAS Number · 111-65-9 
3D model (JSmol) · Interactive image
Beilstein Reference · 1696875
ChEBI · CHEBI:17590 
ChEMBL · ChEMBL134886 
ChemSpider · 349 
DrugBank · DB02440 
ECHA InfoCard · 100.003.539
EC Number · 203-892-1
Gmelin Reference · 82412
KEGG · C01387 
MeSH · octane
PubChem CID · 356
RTECS number · RG8400000
UNII · X1RV0B2FJV 
UN number · 1262
CompTox Dashboard (EPA) · DTXSID0026882
SMILES
CCCCCCCC
Properties
Chemical formula · C8H18
Molar mass · 114.232 g·mol−1
Appearance · Colourless liquid
Odor · Gasoline-like[2]
Density · 0.6986 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
Solubility in water · 0.07 mg / 100 g (at 298 K)[3]
log P · 4.783
Vapor pressure · 1.47 kPa (at 20.0 °C)
Henry's law
constant (kH) · 29 nmol/(Pa·kg)
Conjugate acid · Octonium
Magnetic susceptibility (χ) · −96.63·10−6 cm3/mol
Refractive index (nD) · 1.398
Viscosity · 0.509 mPa·s (25 °C)[4]
0.542 mPa·s (20 °C)
Thermochemistry
Heat capacity (C) · 255.68 J/(K·mol)
Std molar
entropy (S⦵298) · 361.20 J/(K·mol)
Std enthalpy of
formation (ΔfH⦵298) · −252.1 to −248.5 kJ/mol
Std enthalpy of
combustion (ΔcH⦵298) · −5.53 to −5.33 MJ/mol
Hazards
GHS labelling:
Pictograms
Signal word · Danger
Hazard statements · H225, H304, H315, H336, H410
Precautionary statements · P210, P261, P273, P301+P310, P331
NFPA 704 (fire diamond) · 1
3
0
Flash point · 13.0 °C (55.4 °F; 286.1 K)
Autoignition
temperature · 220.0 °C (428.0 °F; 493.1 K)
Explosive limits · 0.96 – 6.5%
Lethal dose or concentration (LD, LC):
LDLo (lowest published) · 428 mg/kg (mouse, intravenous)[5]
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 · Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane

Octane is a hydrocarbon and also 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.

Octane is a component of gasoline and petroleum. Under standard temperature and pressure, octane is a colorless liquid. Like other short-chained alkanes with a low molecular weight, it is volatile, flammable, and toxic. Octane is 1.2 to 2 times more toxic than heptane.[6]

Isomers#edit

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 superimp
(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. Image: source and license

Achiral isomers:

Chiral isomers:

Production and use#edit

In petrochemistry, octanes are not typically differentiated or purified as specific compounds. Octanes are components of particular boiling fractions.[7]

A common route to such fractions is the alkylation reaction between iso-butane and 1-butene, which forms iso-octane.[8]

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#edit

  1. ^ "octane - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 16 September 2004. Identification and Related Records. Retrieved 6 January 2012.
  2. ^ a b c d "#0470". NIOSH Pocket Guide to Chemical Hazards. National Institute for Occupational Safety and Health.
  3. ^ "IUPAC-NIST Solubilities Database". Srdata.nist.gov. Retrieved May 27, 2026.
  4. ^ 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.
  5. ^ "Octane". Immediately Dangerous to Life or Health Concentrations. National Institute for Occupational Safety and Health.
  6. ^ "1988 OSHA PEL Project - Octane | NIOSH | CDC". Cdc.gov. 2020-02-27. Retrieved 2024-04-19.
  7. ^ "Fractionation". Appliedcontrol.com. Retrieved 2024-04-19.
  8. ^ 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.
Categories Alkanes

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