Isopentane

Isopentane, also called methylbutane or 2-methylbutane, is a branched-chain saturated hydrocarbon (an alkane) with five carbon atoms, with formula C
5H
12 or CH(CH
3)
2(C
2H
5).

Isopentane
Names
Preferred IUPAC name
2-Methylbutane[1]
Other names
Isopentane
Identifiers
3D model (JSmol)
1730723
ChEBI
ChemSpider
ECHA InfoCard 100.001.039
EC Number
  • 201-142-8
49318
MeSH isopentane
RTECS number
  • EK4430000
UNII
UN number 1265
Properties
C5H12
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-vis (λmax) 192 nm
1.354
Viscosity 0.214 cP (at 20 °C)
Thermochemistry
164.85 J K−1 mol−1
260.41 J K−1 mol−1
Std enthalpy of
formation (ΔfH⦵298)
 −179.1–−177.3 kJ mol−1
Std enthalpy of
combustion (ΔcH⦵298)
 ~ 3.3 MJ mol−1, 19,664 Btu/lb
Hazards
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H224, H304, H336, H411
P210, P261, P273, P301+310, P331
NFPA 704 (fire diamond)
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
4
1
0
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
 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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Infobox references

Isopentane is an extremely volatile and extremely flammable liquid at room temperature and pressure. It is also the least dense liquid at standard conditions. 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]

Nomenclature

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.

Isomers

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

Uses

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]

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References
  1. 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. 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.CS1 maint: multiple names: authors list (link) CS1 maint: extra text: authors list (link)
  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. http://www.uab.edu/research/administration/offices/ARP/ComparativePathology/Pathology/Histopathology/TissueSubmission/Pages/Freezing-Tissues-for-Cryosectioning.aspx
  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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