Pentane

Pentane
Image:Pentane-2D-Skeletal.svg
Image:Pentane-3D-space-filling.png
IUPAC name	pentane
Other names	n-pentane amyl hydride Skellysolve
Identifiers
CAS number	[109-66-0]
RTECS number	RZ9450000
SMILES	CCCCC
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	0.01 g/100 ml (20 °C)
Acidity (pKa)	~45
Viscosity	0.240 cP at 20 °C
Hazards
MSDS	External MSDS
Main hazards	Highly flammable (F+)
NFPA 704	4 1 0
R/S statement	R: R12, R51/53, R65, R66, R67 S: (S2), S9, S16, S29, S33, S61, S62
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
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Pentane, also known as amyl hydride or skellysolve A is an alkane hydrocarbon. It is a liquid commodity chemical compound, mainly used as fuel and as a solvent.

Molecular structure

The conformation (shape) of pentane is linear, similar to that of butane, but one carbon atom longer.

Isomers

Pentane is one of three structural isomers with the molecular formula C₅H₁₂, the others being isopentane and neopentane.

The branched isomers are more stable than pentane, which means that they have lower heat of formation and heat of combustion. Isopentane is more stable than pentane by 1.8 kcal/mol, and neopentane by 5 kcal/mol.^[1]

A related cycloalkane is cyclopentane, although this is not an isomer of pentane as its molecular formula is different − cyclopentane is an isomer of the pentenes.

Uses

Being an unfunctionalized hydrocarbon, pentane is a commodity chemical. It is mainly a fuel and a solvent, although it also could be used as a source of H₂ via steam reforming.

As the most volatile hydrocarbon that is liquid at room temperature, pentane is often used in the laboratory as a solvent that can be conveniently evaporated. Also because of its nonpolarity and lack of functionality, its dissolving power is poor, thus only non-polar or alkyl-rich compounds are soluble in it. Pentane is completely miscible, however, with many common solvents such as chlorocarbons, aromatics, ethers, but not short chain amines or short chain alcohols.

Reactions

Pentane burns to form carbon dioxide and water:

C₅H₁₂ + 8 O₂ → 5 CO₂ + 6 H₂O

When oxygen is limited, carbon, partially oxidized carbon (soot), and carbon monoxide are also formed.

As for other hydrocarbons, pentane undergoes free radical chlorination:

C₅H₁₂ + Cl₂ → C₅H₁₁Cl + HCl

Such reactions are unselective, yielding a mixture of the 1-, 2-, and 3-chloropentanes, as well as more highly chlorinated derivatives. Other radical halogenations can also occur.

Whereas n-butane is the conventional feedstock in duPont's synthesis maleic anhydride, pentane is also a substrate:

CH₃CH₂CH₂CH₂CH₃ + 5 O₂ → C₂H₂(CO)₂O + 5 H₂O + CO₂

References

1. ^ From the values listed at Standard enthalpy change of formation (data table).

External links

• International Chemical Safety Card 0534
• NIOSH Pocket Guide to Chemical Hazards

• Molview from bluerhinos.co.uk See pentane in 3D
• Material Safety Data Sheet for Pentane
• Phytochemical database entry

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