Pentane
From Wikipedia, the free encyclopedia
| n-Pentane | |
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| IUPAC name |
pentane
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| Other names | n-pentane amyl hydride Skellysolve A |
| Identifiers | |
| CAS number | 109-66-0  |
| PubChem | 8003 |
| RTECS number | RZ9450000 |
| SMILES |
CCCCC
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| InChI |
1/C5H12/c1-3-5-4-2/h3-5H2,1-2H3
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| ChemSpider ID | 7712 |
| Properties | |
| Molecular formula | C5H12 |
| Molar mass | 72.15 g/mol |
| Appearance | Colourless liquid |
| Density | 0.626 g/cm³, liquid |
| Melting point |
−129.8 °C (143 K) |
| Boiling point |
36.1 °C (308 K) |
| Solubility in water | 0.004 g/100 mL (20 °C)[1] |
| Acidity (pKa) | ~45 |
| Viscosity | 0.240 cP at 20 °C |
| Hazards | |
| MSDS | External MSDS |
| R/S statement | R: R12, R51/53, R65, R66, R67 S: (S2), S9, S16, S29, S33, S61, S62 |
| NFPA 704 |
 4
1
0
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| Flash point | −49 °C |
| Related compounds | |
| Related alkanes | Butane, Isopentane, Neopentane, Hexane |
| Related compounds | Cyclopentane |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| (what is this?) (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
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:
| Common name | normal pentane unbranched pentane n-pentane |
isopentane | neopentane |
| IUPAC name | pentane | methylbutane | dimethylpropane |
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In the IUPAC nomenclature, however, pentane means exclusively the n-pentane isomer; the other two being called "methylbutane" and "dimethylpropane".
Pentanes are components of some fuels and are employed as a specialty solvents in the laboratory. Their properties are very similar to those of butanes and hexanes.
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[edit] Industrial uses
Pentane is one of the primary blowing agents used in the production of polystyrene foam.
Due to its low boiling point, low cost, and relative safety, pentane is used as a working medium in geothermal power stations.
[edit] Laboratory use
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.
[edit] Physical properties
| Isomer | M. P. (°C)[2] | B. P. (°C)[2] | Dens (g/l)[2] |
| n-pentane | -129.8 | 36.0 | 621 |
| isopentane | -159.9 | 27.7 | 616 |
| neopentane | -16.6 | 9.5 | 586 |
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.
On the other hand, the melting point of isopentane is only 30°C higher than that of n-pentane, but that of neopentane is more than 100°C above isopentane. The anomaly has been attributed to the better solid-state packing assumed to be possible with the tetrahedral neopentane molecule; but this explanation has been challenged on account of it having a lower density than the other two isomers.[2]
The branched isomers are more stable (have lower heat of formation and heat of combustion) than normal pentane. The difference is 1.8 kcal/mol for isopentane, and 5 kcal/mol for neopentane.[3]
Rotation about two central single C-C bonds of n-pentane produces four different conformations.[4]
[edit] Reactions
All pentane isomers burn with oxygen to form carbon dioxide and water:
- C5H12 + 8 O2 → 5 CO2 + 6 H2O
As with other hydrocarbons, pentanes undergo free radical chlorination:
- 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.
While n-butane is the conventional feedstock in the production of maleic anhydride, n-pentane is also a substrate:
- CH3CH2CH2CH2CH3 + 5 O2 → C2H2(CO)2O + 5 H2O + CO2
[edit] References
- ^ Itrust.de
- ^ a b c d 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}}
- ^ 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. doi:.
[edit] External links
- International Chemical Safety Card 0534 at ILO.org
- NIOSH Pocket Guide to Chemical Hazards at CDC.gov
- Material safety data sheet for Pentane at Ox.ac.uk
- Phytochemical data for pentane at Ars-grin.gov
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