|Jmol 3D model||Interactive image|
|Molar mass||72.15 g·mol−1|
|Density||0.626 g mL−1|
|Melting point||−130.5 to −129.1 °C; −202.8 to −200.3 °F; 142.7 to 144.1 K|
|Boiling point||35.9 to 36.3 °C; 96.5 to 97.3 °F; 309.0 to 309.4 K|
|40 mg L−1 (at 20 °C)|
|Vapor pressure||57.90 kPa (at 20.0 °C)|
|7.8 nmol Pa−1 kg−1|
|UV-vis (λmax)||200 nm|
Refractive index (nD)
|Viscosity||0.240 cP (at 20 °C)|
|167.19 J K−1 mol−1|
|263.47 J K−1 mol−1|
Std enthalpy of
|−174.1–−172.9 kJ mol−1|
Std enthalpy of
|−3.5095–−3.5085 MJ mol−1|
|Supplementary data page|
|Refractive index (n),
Dielectric constant (εr), etc.
|UV, IR, NMR, MS|
|what is ?)(|
Pentane is an organic compound with the formula C5H12 — that is, an alkane with five carbon atoms. The term may refer to any of three structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, pentane means exclusively the n-pentane isomer; the other two being called isopentane (methylbutane) and neopentane (dimethylpropane). Cyclopentane is not an isomer of pentane.
|Common name||normal pentane
Pentanes are relatively inexpensive and are the most volatile alkanes that are liquid at room temperature, so they are often used in the laboratory as solvents that can be conveniently evaporated. However, because of their nonpolarity and lack of functionality, they can only dissolve non-polar and alkyl-rich compounds. Pentanes are miscible with most common nonpolar solvents such as chlorocarbons, aromatics, and ethers. They are also often used in liquid chromatography.
The boiling points of the pentane isomers range from about 9 to 36 °C. As is the case for other alkanes, the more branched isomers tend to have lower boiling points.
The same trend normally holds for the melting points of alkane isomers, and indeed that of isopentane is 30 °C lower than that of n-pentane. However, the melting point of neopentane, the most heavily branched of the three, is 100 °C higher than that of isopentane. The anomalously high melting point of neopentane has been attributed to the better solid-state packing assumed to be possible with its tetrahedral molecule; but this explanation has been challenged on account of it having a lower density than the other two isomers.
Like other alkanes, pentanes are under standard room temperature and conditions largely unreactive - however, with sufficient activation energy (i.e. an open flame), they get readily oxidized to form carbon dioxide and water:
- C5H12 + 8 O2 → 5 CO2 + 6 H2O + heat/ energy
- C5H12 + Cl2 → C5H11Cl + HCl
Such reactions are unselective; with n-pentane, the result is a mixture of the 1-, 2-, and 3-chloropentanes, as well as more highly chlorinated derivatives. Other radical halogenations can also occur.
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- Record of n-Pentane in the GESTIS Substance Database of the IFA, accessed on 19 April 2011
- 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
- Milne, ed., G.W.A. (2005). Gardner's Commercially Important Chemicals: Synonyms, Trade Names, and Properties. Hoboken, New Jersey: John Wiley & Sons, Inc. p. 477. ISBN 978-0-471-73518-2.
- From the values listed at Standard enthalpy change of formation (data table).
- Roman M. Balabin (2009). "Enthalpy Difference between Conformations of Normal Alkanes: Raman Spectroscopy Study of n-Pentane and n-Butane". J. Phys. Chem. A. 113 (6): 1012–9. PMID 19152252. doi:10.1021/jp809639s.