Article · Wikipedia archive · Last revised Jul 19, 2026

2-Methylpentane

2-Methylpentane, trivially known as isohexane, is a branched-chain alkane with the molecular formula C6H14. It is a structural isomer of hexane composed of a methyl group bonded to the second carbon atom in a pentane chain.

Last revised
Jul 19, 2026
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≈ 2 min
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Citations
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Source
2-Methylpentane
Skeletal formula of 2-methylpentane
Skeletal formula of 2-methylpentane source ↗
Ball-and-Stick model of 2-methylpentane
Ball-and-Stick model of 2-methylpentane source ↗
Names
Preferred IUPAC name
2-Methylpentane2
Other names
Isohexane1
Identifiers
3D model (JSmol)
1730735
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.003.204
EC Number
  • 203-523-4
MeSH 2-methylpentane
RTECS number
  • SA2985000
UNII
UN number 1208
  • InChI=1S/C6H14/c1-4-5-6(2)3/h6H,4-5H2,1-3H3 checkY
    Key: AFABGHUZZDYHJO-UHFFFAOYSA-N checkY
  • CCCC(C)C
Properties
C6H14
Molar mass 86.178 g·mol−1
Appearance Colorless liquid
Odor Odorless
Density 653 mg mL−1
Melting point −160 to −146 °C; −256 to −231 °F; 113 to 127 K
Boiling point 60 to 62 °C; 140 to 143 °F; 333 to 335 K
log P 3.608
Vapor pressure 46.7 kPa (at 37.7 °C)
5.7 nmol Pa−1 kg−1
−75.26·10−6 cm3/mol
1.371
Thermochemistry
194.19 J K−1 mol−1
290.58 J K−1 mol−1
−205.3 – −203.3 kJ mol−1
Hazards
GHS labelling:
GHS02: Flammable GHS07: Exclamation mark GHS08: Health hazard GHS09: Environmental hazard
Danger
H225, H304, H315, H336, H411
P210, P261, P273, P301+P310, P331
NFPA 704 (fire diamond)
Flash point −7 °C (19 °F; 266 K)
306 °C (583 °F; 579 K)
Explosive limits 1.2–7%
NIOSH (US health exposure limits):
PEL (Permissible)
none3
Related compounds
Related alkanes
Related compounds
2-Ethyl-1-butanol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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2-Methylpentane, trivially known as isohexane, is a branched-chain alkane with the molecular formula C6H14. It is a structural isomer of hexane composed of a methyl group bonded to the second carbon atom in a pentane chain.

As of early 1990s, it was present in American4 and European5 gasoline in small amounts, and by 2011 its share in US gas varied between 2 and 8%.6 Using a quantitative structure-activity relationship (QSAR) prediction model, 2-Methylpentane has a research octane number (RON) of 75, motor octane number (MON) of 77, and cetane number (CN) of 29.7

See also

See also

References

References

  1. Haynes, William M. (2010). Handbook of Chemistry and Physics (91 ed.). Boca Raton, Florida, USA: CRC Press. p. 3-364. ISBN 978-1-43982077-3.
  2. International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. P-15.1.7.1.4. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
  3. NIOSH Pocket Guide to Chemical Hazards. "#0323". National Institute for Occupational Safety and Health (NIOSH).
  4. Doskey, Paul V.; Porter, Joseph A.; Scheff, Peter A. (November 1992). "Source Fingerprints for Volatile Non-Methane Hydrocarbons". Journal of the Air & Waste Management Association. 42 (11): 1437–1445. Bibcode:1992JAWMA..42.1437D. doi:10.1080/10473289.1992.10467090. ISSN 1047-3289.
  5. Östermark, Ulf; Petersson, Göran (1992-09-01). "Assessment of hydrocarbons in vapours of conventional and alkylate-based petrol" (PDF). Chemosphere. 25 (6): 763–768. Bibcode:1992Chmsp..25..763O. doi:10.1016/0045-6535(92)90066-Z. ISSN 0045-6535.
  6. "Hydrocarbon Composition of Gasoline Vapor Emissions from Enclosed Fuel Tanks". nepis.epa.gov. United States Environmental Protection Agency. 2011.
  7. Do, Phuong T. M.; Crossley, Steven; Santikunaporn, Malee; Resasco, Daniel E. (2007). "Catalytic strategies for improving specific fuel properties". Catalysis. pp. 33–64. doi:10.1039/b602366p. ISBN 978-0-85404-244-9.