Pentane


Pentane
n-Pentane
Identifiers
CAS number 109-66-0 YesY
PubChem 8003
ChemSpider 7712 YesY
UNII 4FEX897A91 N
DrugBank DB03119
ChEBI CHEBI:37830 N
ChEMBL CHEMBL16102 YesY
RTECS number RZ9450000
Jmol-3D images Image 1
Properties
Molecular formula C5H12
Molar mass 72.15 g/mol
Appearance Colourless liquid
Density 0.626 g/mL, liquid
Melting point

−129.8 °C (143 K)

Boiling point

36.1 °C (308 K)

Solubility in water 0.04 g/L (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
Main hazards Highly flammable (F+)
Harmful (Xn)
Dangerous for the environment (N)
NFPA 704
NFPA 704.svg
4
1
0
Flash point – 49 °C
Autoignition
temperature
260 °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
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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: in the IUPAC nomenclature, however, pentane means exclusively the n-pentane isomer; the other two being called "methylbutane" and "dimethylpropane". Cyclopentane is not an isomer of pentane.

Pentanes are components of some fuels and are employed as specialty solvents in the laboratory. Their properties are very similar to those of butanes and hexanes.

Contents

Isomers

Common name normal pentane
unbranched pentane
n-pentane
isopentane neopentane
IUPAC name pentane methylbutane dimethylpropane
Molecular
diagram
N-Pentan.png Isopentane.PNG Neopentane.PNG
Skeletal
diagram
Pentane-2D-Skeletal.svg Isopentane-2D-skeletal.png Neopentane-2D-skeletal.png

Industrial uses

Pentane is one of the primary blowing agents used in the production of polystyrene foam.

Because of its low boiling point, low cost, and relative safety, pentane is used as a working medium in geothermal power stations. It is added into some refrigerant blends as well.

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.

Physical properties

Melting point (MP), boiling point (BP) and density of pentanes[2]
Isomer MP (°C) BP (°C) Density (g/L)
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.

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 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.[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]

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

References

  1. ^ Record of n-Pentane in the GESTIS Substance Database from the IFA, accessed on 19 April 2011
  2. ^ a b 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. ^ From the values listed at Standard enthalpy change of formation (data table).
  4. ^ 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:10.1021/jp809639s. PMID 19152252. 

External links


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Look at other dictionaries:

  • Pentane — Général Nom IUPAC pentane …   Wikipédia en Français

  • pentane — [ pɛ̃tan ] n. m. • 1874; de penta ♦ Chim. Hydrocarbure saturé (C5H12), cinquième terme de la série des alcanes. ● pentane nom masculin Hydrocarbure saturé C5H12, présent dans les fractions légères du pétrole. pentane [pɛ̃tan] n. m. ÉTYM. 1874; de …   Encyclopédie Universelle

  • Pentane — Pentane,   Singular Pentan das, s, zu den Alkanen zählende aliphatischen Kohlenwasserstoffe mit der Summenformel C5H12, die in drei Strukturisomeren auftreten (n Pentan, Isopentan, Neopentan). Die Pentane sind flüssige, farblose, leicht… …   Universal-Lexikon

  • Pentane — Pen tane, n. [See {Penta }.] (Chem.) Any one of the three metameric hydrocarbons, {C5H12}, of the methane or paraffin series. They are colorless, volatile liquids, two of which occur in petroleum. So called because of the five carbon atoms in the …   The Collaborative International Dictionary of English

  • Pentane — C5H12, drei isomere Grenzkohlenwasserstoffe, normales Pentan, Dimethyläthylmethan und Tetramethylmethan, finden sich zum Teil im Erdöl und sieden bei 38°, bez. 30° und 10° …   Meyers Großes Konversations-Lexikon

  • Pentane — Pentāne, zwischen 30 und 40° siedende Kohlenwasserstoffe mit 5 Kohlen und 12 Wasserstoffatomen …   Kleines Konversations-Lexikon

  • pentane — [pen′tān΄] n. [ PENT(A) + ANE] any of three known isomeric, colorless alkanes, C5H12, occurring in petroleum, etc.: used as a solvent, in low temperature thermometers, etc …   English World dictionary

  • pentane — /pen tayn/, n. Chem., Pharm. 1. a hydrocarbon of the methane series, existing in three liquid isomeric forms. 2. Also called normal pentane. the most important isomer of pentane, a colorless, flammable, water insoluble, very volatile liquid,… …   Universalium

  • Pentane — Eigenschaften der Pentane[1] Name n Pentan[2] Isopentan[3] Neopentan[4] Andere Namen …   Deutsch Wikipedia

  • pentane — noun An aliphatic hydrocarbon of chemical formula CH; either of the three isomers n pentane, methyl butane (isopentane), and di methyl propane (neopentane); volatile liquids under normal conditions …   Wiktionary


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