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Skeletal formula of isopentane
Skeletal formula of isopentane with all implicit carbons shown, and all explicit hydrogens added
Ball and stick model of isopentane
Preferred IUPAC name
Other names
3D model (JSmol)
ECHA InfoCard 100.001.039 Edit this at Wikidata
EC Number
  • 201-142-8
MeSH isopentane
RTECS number
  • EK4430000
UN number 1265
  • InChI=1S/C5H12/c1-4-5(2)3/h5H,4H2,1-3H3 checkY
  • CCC(C)C
Molar mass 72.151 g·mol−1
Appearance Colorless liquid
Odor Odorless
Density 616 mg mL−1[2]
Melting point −161 to −159 °C; −258 to −254 °F; 112 to 114 K
Boiling point 27.8 to 28.2 °C; 81.9 to 82.7 °F; 300.9 to 301.3 K
Vapor pressure 76.992 kPa (at 20 °C)
7.2 nmol Pa−1 kg−1
UV-vismax) 192 nm
Viscosity 0.214 cP (at 20 °C)
164.85 J K−1 mol−1
260.41 J K−1 mol−1
−179.1–−177.3 kJ mol−1
~ 3.3 MJ mol−1, 19,664 Btu/lb
GHS pictograms GHS02: Flammable GHS07: Harmful GHS08: Health hazard GHS09: Environmental hazard
GHS Signal word Danger
H224, H301, H302, H305, H336, H411
P210, P261, P273, P301+310, P331
NFPA 704 (fire diamond)
Flash point −51 °C (−60 °F; 222 K)
420 °C (788 °F; 693 K)
Explosive limits 1.4–8.3%
Related compounds
Related alkanes
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Isopentane, also called methylbutane or 2-methylbutane, is a branched-chain saturated hydrocarbon (an alkane) with five carbon atoms, with formula C
or CH(CH

Isopentane is an extremely volatile and extremely flammable liquid at room temperature and pressure. It is also the least dense liquid at standard conditions.[citation needed] The normal boiling point is just a few degrees above room temperature and isopentane will readily boil and evaporate away on a warm day.

Isopentane is commonly used in conjunction with liquid nitrogen to achieve a liquid bath temperature of −160 °C. Natural gas typically contains 1% or less isopentane,[3] but it is a significant component of natural gasoline.[4]


The traditional name isopentane was still retained in the 1993 IUPAC recommendations,[5][6] but is no longer recommended according to the 2013 recommendations.[1] The preferred IUPAC name is the systematic name 2-methylbutane. An isopentyl group is a subset of the generic pentyl group. It has the chemical structure -CH3CH2CH(CH3)2.


Isopentane is one of three structural isomers with the molecular formula C5H12, the others being pentane (n-pentane) and neopentane (dimethyl propane).


Isopentane is used in a closed loop in geothermal power production to drive turbines.[7]

Isopentane is used, in conjunction with dry ice or liquid nitrogen, to freeze tissues for cryosectioning in histology. [8]

Isopentane is a major component (sometimes 30% or more) of natural gasoline, an analog of common petroleum-derived gasoline that is condensed from natural gas.[4] It has a substantially higher octane rating (RON 93.7) than n-pentane (61.7), and therefore there is interest in conversion from the latter.[9]


  1. ^ a b Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 652. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4. The names ‘isobutane’, ‘isopentane’ and ‘neopentane’ are no longer recommended.
  2. ^ James Wei (1999), Molecular Symmetry, Rotational Entropy, and Elevated Melting Points. Ind. Eng. Chem. Res., volume 38 issue 12, pp. 5019–5027 doi:10.1021/ie990588m
  3. ^ Georg Hammer, Torsten Lübcke, Roland Kettner, Mark R. Pillarella, Herta Recknagel, Axel Commichau, Hans-Joachim Neumann and Barbara Paczynska-Lahme "Natural Gas" in Ullmann's Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a17_073.pub2
  4. ^ a b Ivan F. Avery, L. V. Harvey (1958): Natural-gasoline and Cycling Plants in the United States, Information circular, U.S. Department of the Interior, Bureau of Mines. 12 pages.
  5. ^ Table 19(a) Acyclic and monocyclic hydrocarbons. Parent hydrocarbons
  6. ^ Panico, R. & Powell, W. H., eds. (1994). A Guide to IUPAC Nomenclature of Organic Compounds 1993. Oxford: Blackwell Science. ISBN 0-632-03488-2.
  7. ^ Byproduct Isopentane also used in some of the LPG plant to run the boiler and generate the power. HS Orka HF Energy Plant IV Archived 2014-10-18 at the Wayback Machine
  8. ^
  9. ^ Sheng Wang, Ying Zhang, Mao-Gang He, Xiong Zheng, and Li-Bin Chen (2014): "Thermal Diffusivity and Speed of Sound of Saturated Pentane from Light Scattering". International Journal of Thermophysics, volume 35, pages 1450–1464. doi:10.1007/s10765-014-1718-x

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