Pentane

{{#if:OdourlessOdourlessColourless liquid626 mg mL⁻¹200 nm40 mg L⁻¹ (at 20 °C)3.25557.90 kPa (at 20.0 °C)7.8 nmol Pa⁻¹ kg⁻¹~45~591.358240 μPa s (at 20 °C)142.7144.1125|! style="background: #F8EABA; text-align: center;" colspan="2" | Properties

Pentane
Skeletal formula of pentane
Skeletal formula of pentane with all explicit hydrogens added
Ball and stick model of pentane	Spacefill model of pentane
IUPAC name Pentane
Identifiers
CAS number	109-66-0 7pxY
PubChem	8003
ChemSpider	7712 7pxY
UNII	4FEX897A91 7pxY
EC number	203-692-4
UN number	1265
DrugBank	DB03119
MeSH	pentane
ChEBI	CHEBI:37830 7pxY
ChEMBL	CHEMBL16102 7pxY
RTECS number	RZ9450000
Beilstein Reference	969132
Gmelin Reference	1766
Jmol-3D images	Image 1
SMILES CCCCC <p><p style="word-wrap: break-word;">
InChI InChI=1S/C5H12/c1-3-5-4-2/h3-5H2,1-2H3 7pxY Key: OFBQJSOFQDEBGM-UHFFFAOYSA-N 7pxY
Molecular formula	C5H12
Molar mass	72.15 g mol−1
Thermochemistry
Std enthalpy of formation ΔfHo298	−174.1–−172.9 kJ mol−1
Std enthalpy of combustion ΔcHo298	−3.5095–−3.5085 MJ mol−1
Standard molar entropy So298	263.47 J K−1 mol−1
Specific heat capacity, C	167.19 J K−1 mol−1
Hazards
MSDS	External MSDS
GHS pictograms	The flame pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The health hazard pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The environment pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word	DANGER
GHS hazard statements	H225, H304, H336, H411
GHS precautionary statements	P210, P261, P273, P301+310, P331
EU Index	601-006-00-1
EU classification	Flammable F+ Harmful Xn Dangerous for the Environment (Nature) N
R-phrases	R12, R51/53, R65, R66, R67
S-phrases	(S2), S16, S29, S33
NFPA 704	75px 4 1 0
Flash point	−49.0 °C
Autoignition temperature	260.0 °C
Explosive limits	1.4–8.3%
LD50	3 g kg−1 (dermal, rabbit) 5 g kg−1 (oral, mouse)
Related compounds
Related alkanes	Butane Butyl iodide Hexane
Supplementary data page
Structure and properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
14pxY (verify) (what is: 10pxY/10pxN?) 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.

Isomers

Common name	normal pentane unbranched pentane n-pentane	isopentane	neopentane
IUPAC name	pentane	2-methylbutane	2,2-dimethylpropane
Molecular diagram	130px	140px	120px
Skeletal diagram	150px	110px	80px
Melting Point (°C)	−129.8	−159.9	−16.6
Boiling Point (°C)	36.0	27.7	9.5
Density (g/L)	621	616	586

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

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.

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.

Rotation about two central single C-C bonds of n-pentane produces four different conformations.

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

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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