Butane

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Butane
General
Molecular formula	C4H10
SMILES	CCCC
Molar mass	58.08 g/mol
Appearance	Colorless gas
CAS number	[106-97-8]
Properties
Density and phase	2.52 g/l, gas (15 °C, 1 atm)
Solubility in water	6.1 mg/100 ml (20 °C)
Melting point	−138.3 °C (134.9 K)
Boiling point	−0.5 °C (272.7 K)
Hazards
MSDS	External MSDS
EU classification	Highly flammable (F+)
NFPA 704	4 1 0
R-phrases	R12
S-phrases	S2, S9, S16
Flash point	−60 °C
Autoignition temperature	487 °C
Explosive limits	1.8–8.4%
Maximum burning temperature	2,350 °C
Supplementary data page
Structure and properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Related alkanes	Propane Pentane
Related compounds	Isobutane
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Butane, also called n-butane, is the unbranched alkane with four carbon atoms, CH₃CH₂CH₂CH₃. Butane is also used as a collective term for n-butane together with its only other isomer, isobutane (also called methylpropane), CH(CH₃)₃.

Butanes are highly flammable, colorless, easily liquefied gases. The name butane was derived by back-formation from the name of butyric acid.

Structures of the two isomers of butane

[edit] Reactions and uses

When oxygen is plentiful, butane burns to form carbon dioxide and water vapor; when oxygen is limited, carbon (soot) or carbon monoxide may also be formed.

2 C₄H₁₀ + 13 O₂ → 8 CO₂ + 10 H₂O

n-Butane is the feedstock for duPont's catalytic process for the preparation of maleic anhydride:

CH₃CH₂CH₂CH₃ + 3.5 O₂ → C₂H₂(CO)₂O + 4 H₂O

n-Butane, like all hydrocarbons, undergoes free radical chlorination providing both 1-chloro- and 2-chlorobutanes, as well as more highly chlorinated derivatives. The relative rates of the chlorination is partially explained by the differing bond dissociation energies, 425 and 411 kJ/mol for the two types of C-H bonds. The two central carbon atoms have the slightly weaker C-H bonds.

Spectrum of the blue flame from a butane torch showing molecular radical band emission and Swan bands.

Butane gas is sold bottled as a fuel for cooking and camping, in which case it is referred to commercially as LPG. It is also used as a petrol component, as a feedstock for the production of base petrochemicals in steam cracking, as fuel for cigarette lighters and as a propellant in aerosol sprays. Despite its flammability, very pure forms of butane are also occasionally used as a refrigerant in automobiles that are set up to use R-12, because R-12 is an ozone depleting halomethane.

[edit] Effects and health issues

Inhaling butane can cause drowsiness, narcosis, asphyxia; cardiac arrhythmia and frostbite, which can result in instant death from Asphyxiation, Acute toxicity and ventricular fibrillation. Butane is the most commonly misused volatile solvent in the UK, and was the cause of 52% of solvent related deaths in 2000.^[1] By spraying butane directly into the throat, the jet of fluid can cool rapidly to –20 °C by expansion, causing prolonged laryngospasm.^[2] "Sudden sniffing death syndrome", first described by Bass in 1970,^[3] is the most common single cause of solvent related death, resulting in 55% of known fatal cases.^[2]

[edit] See also

• Volatile substance abuse
• Camping Gaz
• Calor gas

[edit] References

1. ^ Trends in death Associated with Abuse of Volatile Substances 1971-2004 Field-Smith M, Bland JM, Taylor JC, et al., Department of Public Health Sciences. London: St George’s Medical School
2. ^ ^{a b} Ramsey J, Anderson HR, Bloor K, et al. An introduction to the practice, prevalence and chemical toxicology of volatile substance abuse. Hum Toxicol 1989;8:261–9
3. ^ Bass M. Sudden sniffing death. JAMA 1970;212:2075–9

[edit] External links

• International Chemical Safety Card 0232
• NIOSH Pocket Guide to Chemical Hazards
• European Chemicals Bureau
• n-Butane Molecule of the Month
• Molview from bluerhinos.co.uk See Butane in 3D
• Computational Chemistry Wiki
• Data from Air Liquide
• World LP Gas Association (WLPGA)
• LP Gas Association: Propane and Butane in the UK
• Link page to external chemical sources.