Butane

Butane
Identifiers
CAS number	[106-97-8]
SMILES	CCCC
Properties
Molecular formula	C4H10
Molar mass	58.14 g/mol
Appearance	Colorless gas
Density	2.48 g/l, gas (15 °C, 1 atm)
Melting point	−138 °C (135 K)
Boiling point	−0.5 °C (272.6 K)
Solubility in water	6.1 mg/100 ml (20 °C)
Hazards
EU classification	Highly flammable (F+)
NFPA 704	4 1 0
Flash point	−60 °C
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)

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
• 

  n-Butane

• 

  i-Butane

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.

2C₄H₁₀ + 13O₂ → 8CO₂ + 10H₂O

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

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

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. When blended with Propane and other hydrocarbons, 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.

Very pure forms of butane, especially isobutane, can be used as refrigerants and have largely replaced the ozone layer depleting halomethanes, for instance in household refrigerators and freezers. The flammability of butane is not a major issue because the amount of butane in an appliance is not enough to cause a combustible mix given the amount of air in a room. The system operating pressure for butane is lower than for the halomethanes, such as R-12, so direct conversion of R-12 systems to butane, such as in automotive air conditioning systems, will not function optimally.

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. By spraying butane directly into the throat, the jet of fluid can cool rapidly to –20 °C by expansion, causing prolonged laryngospasm. "Sudden Sniffer's Death syndrome," first described by Bass in 1970, is the most common single cause of solvent related death, resulting in 55% of known fatal cases.

Butane gas cylinder used for cooking

See also

• Volatile substance abuse
• Camping Gaz
• Calor gas

External links

All links retrieved November 8, 2007.

• 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
• World LP Gas Association (WLPGA)
• LP Gas Association: Propane and Butane in the UK
• Global BioSciences In-Situ Bioremediation utilizing Butane
• Butane Viscosity as tunction of temperature and pressure

 

Alkanes

methane CH4

|

ethane C2H6

|

propane C3H8

|

butane C4H10

|

pentane C5H12

|

hexane C6H14

heptane C7H16

|

octane C8H18

|

nonane C9H20

|

decane C10H22

|

undecane C11H24

|

dodecane C12H26

E numbers
Colours (E100-199) • Preservatives (E200-299) • Antioxidants & Acidity regulators (E300-399) • Thickeners, stabilisers & emulsifiers (E400-499) • pH regulators & anti-caking agents (E500-599) • Flavour enhancers (E600-699) • Miscellaneous (E900-999) • Additional chemicals (E1100-1599)
Waxes (E900-909) • Synthetic glazes (E910-919) • Improving agents (E920-929) • Packaging gases (E930-949) • Sweeteners (E950-969) • Foaming agents (E990-999)
Argon (E938) • Helium (E939) • Dichlorodifluoromethane (E940) • Nitrogen (E941) • Nitrous oxide (E942) • Butane (E943a) • Isobutane (E943b) • Propane (E944) • Oxygen (E948) • Hydrogen (E949)

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