Myujth

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.

Octane is a component of gasoline (petrol). As with all low-molecular-weight hydrocarbons, octane is volatile and very flammable.

Use of the term in gasoline

"Octane" is colloquially used as a short form of "octane rating" (an index of a fuel's ability to resist engine knock at high compression, which is a characteristic of octane's branched-chain isomers, especially iso-octane), particularly in the expression "high octane."

The octane rating was originally determined by mixing a gasoline made entirely of heptane and 2,2,4-trimethylpentane (a highly branched octane), and assigning anti-knock ratings of 0 for pure heptane and 100 for pure 2,2,4-trimethylpentane. The anti-knock rating of this mixture would be the same as the percentage of 2,2,4-trimethylpentane in the mix. Modern octane ratings of gasoline are given octane ratings equal to those from this original heptane/octane scale. Different isomers of octane can contribute to a higher or lower octane rating. For example, n-octane (the straight chain of 8 carbon atoms with no branching) has a -10 (negative) octane rating, while pure 2,2,4-trimethylpentane (a highly branched octane) has an octane rating of 100.^{[4][better source needed]} Some fuels have an octane rating higher than 100, notably those containing methanol or ethanol.

Metaphorical use

Octane became well known in American popular culture in the mid- and late 1960s, when gasoline companies boasted of "high octane" levels in their gasoline advertisements.

The compound adjective "high-octane", meaning powerful or dynamic, is recorded in a figurative sense from 1944.^[5] By the mid-1990s, the phrase was commonly being used as an intensifier and has 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

External links

• International Chemical Safety Card 0933


• 
  "NIOSH Pocket Guide to Chemical Hazards #0470". National Institute for Occupational Safety and Health (NIOSH). 
  


• Dr. Duke's Phytochemical and Ethnobotanical Databases, Octane, http://www.ars-grin.gov/cgi-bin/duke/chemical.pl?OCTANE
  

Octane

Names
IUPAC name Octane[1]
Identifiers
CAS Number	111-65-9 Y
3D model (JSmol)	Interactive image
3DMet	B00281
Beilstein Reference	1696875
ChEBI	CHEBI:17590 N
ChEMBL	ChEMBL134886 Y
ChemSpider	349 Y
DrugBank	DB02440 N
ECHA InfoCard	100.003.539
EC Number	203-892-1
Gmelin Reference	82412
KEGG	C01387 Y
MeSH	octane
PubChem CID	356
RTECS number	RG8400000
UN number	1262
InChI InChI=1S/C8H18/c1-3-5-7-8-6-4-2/h3-8H2,1-2H3 Y Key: TVMXDCGIABBOFY-UHFFFAOYSA-N Y
SMILES CCCCCCCC
Properties
Chemical formula	C8H18
Molar mass	114.23 g·mol−1
Appearance	Colorless liquid
Odor	Gasoline-like[2]
Density	0.703 g cm−3
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	0.007 mg dm−3 (at 20 °C)
log P	4.783
Vapor pressure	1.47 kPa (at 20.0 °C)
Henry's law constant (kH)	29 nmol Pa−1 kg−1
Magnetic susceptibility (χ)	-96.63·10−6 cm3/mol
Refractive index (nD)	1.398
Viscosity	542 μPa s (at 20 °C)
Thermochemistry
Heat capacity (C)	255.68 J K−1 mol−1
Std molar entropy (So298)	361.20 J K−1 mol−1
Std enthalpy of formation (ΔfHo298)	−252.1–−248.5 kJ mol−1
Std enthalpy of combustion (ΔcHo298)	−5.53–−5.33 MJ mol−1
Hazards
GHS pictograms
GHS signal word	DANGER
GHS hazard statements	H225, H304, H315, H336, H410
GHS precautionary statements	P210, P261, P273, P301+310, P331
NFPA 704
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)[3]
US health exposure limits (NIOSH):
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	Heptane Nonane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references