View source for Octane

{{Short description|Hydrocarbon compound with the formula C8H18}}
{{Distinguish|octene|octyne}}
{{for-multi|the gasoline rating system|Octane rating|other uses}} {{Chembox
| ImageFile      = Octane-2D-Skeletal.svg
| ImageClass = skin-invert-image
| ImageFile1     = OctaneFull.png
| ImageClass1 = skin-invert-image
| ImageFile2     = Octane 3D ball.png
| ImageClass2 = bg-transparent
| ImageFile3     = N-octane-spaceFilling.png
| ImageClass3 = bg-transparent
| ImageAlt       = Skeletal formula of octane
| ImageFile_Ref  = {{chemboximage|correct|??}}
| ImageAlt1      = Skeletal formula of octane with all implicit carbons shown, and all explicit hydrogens added
| ImageFile1_Ref = {{chemboximage|correct|??}}
| ImageAlt2      = Ball-and-stick model of octane
| ImageFile2_Ref = {{chemboximage|correct|??}}
| ImageSize3     = 160
| ImageAlt3      = Space-filling model of octane
| ImageFile3_Ref = {{chemboximage|correct|??}}
| OtherNames     = ''n''-Octane
| SystematicName = Octane<ref>{{Cite web|title=octane - Compound Summary|url=https://pubchem.ncbi.nlm.nih.gov/compound/356|work=PubChem Compound|publisher=National Center for Biotechnology Information|access-date=6 January 2012|location=USA|date=16 September 2004|at=Identification and Related Records}}</ref>
| Section1       = {{Chembox Identifiers
| CASNo = 111-65-9
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = X1RV0B2FJV
| PubChem = 356
| ChemSpiderID = 349
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| EINECS = 203-892-1
| UNNumber = 1262
| DrugBank = DB02440
| DrugBank_Ref = {{drugbankcite|changed|drugbank}}
| KEGG = C01387
| KEGG_Ref = {{keggcite|correct|kegg}}
| MeSHName = octane
| ChEBI = 17590
| ChEBI_Ref = {{ebicite|changed|EBI}}
| ChEMBL = 134886
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| RTECS = RG8400000
| Beilstein = 1696875
| Gmelin = 82412
| 3DMet = B00281
| SMILES = CCCCCCCC
| StdInChI = 1S/C8H18/c1-3-5-7-8-6-4-2/h3-8H2,1-2H3
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = TVMXDCGIABBOFY-UHFFFAOYSA-N
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
}}
| Section2       = {{Chembox Properties
| Formula = {{chem2|CH3(CH2)6CH3}}
| C=8|H=18
| Appearance = Colourless liquid
| Odor = Gasoline-like<ref name=PGCH/>
| Density = 0.703 g/cm<sup>3</sup>
| MeltingPtK = 216.0 to 216.6
| BoilingPtK = 398.2 to 399.2
| Solubility = 0.07 mg / 100 g (at 298 K) <ref>https://srdata.nist.gov/solubility/sol_detail.aspx?sysID=38_103</ref>
| LogP = 4.783
| VaporPressure = 1.47 kPa (at 20.0&nbsp;°C)
| HenryConstant = 29 nmol/(Pa·kg)
| RefractIndex = 1.398
| Viscosity = {{plainlist|
* 0.509 mPa·s (25&nbsp;°C)<ref name="Dymond1994">{{cite journal|last1=Dymond|first1=J. H.|last2=Oye|first2=H. A.|title=Viscosity of Selected Liquid ''n''-Alkanes|journal=Journal of Physical and Chemical Reference Data|volume=23|issue=1|year=1994|pages=41–53|issn=0047-2689|doi=10.1063/1.555943|bibcode=1994JPCRD..23...41D}}</ref>
* 0.542 mPa·s (20&nbsp;°C)}}
| MagSus = −96.63·10<sup>−6</sup> cm<sup>3</sup>/mol
| ConjugateAcid = [[Octonium]]
}}
| Section3       = {{Chembox Thermochemistry
| DeltaHf = −252.1 to −248.5 kJ/mol
| DeltaHc = −5.53 to −5.33 MJ/mol
| Entropy = 361.20 J/(K·mol)
| HeatCapacity = 255.68 J/(K·mol)
}}
| Section4       = {{Chembox Hazards
| GHSPictograms = {{GHS flame}} {{GHS exclamation mark}} {{GHS health hazard}} {{GHS environment}}
| GHSSignalWord = '''DANGER'''
| NFPA-H = 1
| NFPA-F = 3
| NFPA-R = 0
| HPhrases = {{H-phrases|225|304|315|336|410}}
| PPhrases = {{P-phrases|210|261|273|301+310|331}}
| FlashPtC = 13.0
| AutoignitionPtC = 220.0
| ExploLimits = 0.96 – 6.5%
| IDLH = 1000 ppm<ref name=PGCH>{{PGCH|0470}}</ref>
| REL = TWA 75 ppm (350 mg/m<sup>3</sup>) C 385 ppm (1800 mg/m<sup>3</sup>) [15-minute]<ref name=PGCH/>
| PEL = TWA 500 ppm (2350 mg/m<sup>3</sup>)<ref name=PGCH/>
| LDLo = 428 mg/kg (mouse, intravenous)<ref>{{IDLH|111659|Octane}}</ref>
}}
| Section5       = {{Chembox Related
| OtherFunction_label = alkanes
| OtherFunction = {{Unbulleted list|[[Methane]]|[[Ethane]]|[[Propane]]|[[Butane]]|[[Pentane]]|[[Hexane]]|[[Heptane]]|}}
}}
| Verifiedfields = changed
| Watchedfields  = changed
| verifiedrevid  = 411133144
}}

'''Octane''' is a [[hydrocarbon]] and also an [[alkane]] with the [[chemical formula]] C<sub>8</sub>H<sub>18</sub>, and the condensed structural formula CH<sub>3</sub>(CH<sub>2</sub>)<sub>6</sub>CH<sub>3</sub>. Octane has many [[structural isomer]]s that differ by the location of branching in the [[carbon chain]]. One of these isomers, [[2,2,4-Trimethylpentane|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 an odorless, colorless liquid. Like other short-chained alkanes with a low molecular weight, it is [[Volatility (chemistry)|volatile]], flammable, and toxic. Octane is 1.2 to 2 times more toxic than [[heptane]].<ref>{{Cite web |date=2020-02-27 |title=1988 OSHA PEL Project - Octane {{!}} NIOSH {{!}} CDC |url=https://www.cdc.gov/niosh/pel88/111-65.html |access-date=2024-04-19 |website=www.cdc.gov }}</ref>

==Isomers==
N-octane has 23 [[Structural isomers|constitutional isomers]]. 8 of these isomers have one [[stereocenter]]; 3 of them have two stereocenters.
[[File:Octane_stereo_isomers_10_3_4_dimethylhexane.svg|thumb|437x437px|[[3,4-Dimethylhexane|(3''S'',4''S'')-3,4-Dimethylhexane]] (top left) and [[3,4-Dimethylhexane|(3''R'',4''R'')-3,4-Dimethylhexane]] (top right) are non-superimposable mirror images, so they are chiral [[enantiomer]]s. [[3,4-Dimethylhexane|(''meso'')-3,4-Dimethylhexane]] (bottom) has a superimposable mirror image, so it is an achiral [[meso compound]].]]
'''Achiral isomers:'''

* [[2-Methylheptane]]
* [[4-Methylheptane]]
* [[3-Ethylhexane]]
* [[2,2-Dimethylhexane]]
* [[2,5-Dimethylhexane]]
* [[3,4-Dimethylhexane|(''meso'')-3,4-Dimethylhexane]]
* [[3,3-Dimethylhexane]]
* [[3-Ethyl-2-methylpentane]]
* [[3-Ethyl-3-methylpentane]]
* [[2,2,4-Trimethylpentane]] (i.e. iso-octane)
* [[2,3,3-Trimethylpentane]]
* [[2,3,4-Trimethylpentane]]
* [[2,2,3,3-Tetramethylbutane]]

'''Chiral isomers:'''

* [[3-Methylheptane|(3''R'')-3-Methylheptane]]
* [[3-Methylheptane|(3''S'')-3-Methylheptane]]
* [[2,3-Dimethylhexane|(3''R'')-2,3-Dimethylhexane]]
* [[2,3-Dimethylhexane|(3''S'')-2,3-Dimethylhexane]]
* [[2,4-Dimethylhexane|(4''R'')-2,4-Dimethylhexane]]
* [[2,4-Dimethylhexane|(4''S'')-2,4-Dimethylhexane]]
* [[3,4-Dimethylhexane|(3''R'',4''R'')-3,4-Dimethylhexane]]
* [[3,4-Dimethylhexane|(3''S'',4''S'')-3,4-Dimethylhexane]]
* [[2,2,3-Trimethylpentane|(3''R'')-2,2,3-Trimethylpentane]]
* [[2,2,3-Trimethylpentane|(3''S'')-2,2,3-Trimethylpentane]]

== Production and use ==
In petrochemistry, octanes are not typically differentiated or purified as specific compounds.  Octanes are components of particular boiling fractions.<ref>{{Cite web |title=Fractionation |url=https://www.appliedcontrol.com/industries/midstream-oil-and-gas/natural-gas-processing/fractionation/ |access-date=2024-04-19 |website=www.appliedcontrol.com }}</ref>

A common route to such fractions is the [[Alkylation|alkylation reaction]] between iso-butane and 1-butene, which forms iso-octane.<ref>{{Cite journal |last=Ross |first=Julian |date=January 1986 |title=Ullmann's Encyclopedia of industrial chemistry |url=http://dx.doi.org/10.1016/s0166-9834(00)82943-7 |journal=Applied Catalysis |volume=27 |issue=2 |pages=403–404 |doi=10.1016/s0166-9834(00)82943-7 |issn=0166-9834|url-access=subscription }}</ref>

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

{| class="wikitable sortable mw-collapsible"
|[[File:N-octane.jpg|none|thumb|338x338px|''N-octane'' is the octane isomer that has the longest carbon skeleton. Unlike its constitutional isomers, it has a very low knock resistance.]]
|[[File:Iso-octane.jpg|none|thumb|271x271px|The octane isomer, ''iso-octane'', is used as one of the standards for octane ratings. It has a rating of 100 by definition.]]
|[[File:2,3,3-Trimethylpentane_(view_2).jpg|none|thumb|224x224px|The octane isomer ''2,3,3-Trimethylpentane'' has an octane rating exceeding 100.]]
|}

==References==
<references />

==External links==
* {{ICSC|0933|09}}
* {{PGCH|0470}}
* Dr. Duke's Phytochemical and Ethnobotanical Databases, Octane, [https://archive.today/20121213000953/http://www.ars-grin.gov/cgi-bin/duke/chemical.pl?OCTANE]

{{Alkanes}}
{{Hydrides by group}}

[[Category:Alkanes]]
[[Category:Hydrocarbons]]