Butane

Butane

Skeletal formula of butane
Names
IUPAC name Butane
Other names Butyl hydride Methylethylmethane
Identifiers
CAS Number	106-97-8 Y
Beilstein Reference	969129
ChEBI	CHEBI:37808 Y
ChEMBL	ChEMBL134702 Y
ChemSpider	7555 Y
EC Number	203-448-7
Gmelin Reference	1148
Jmol 3D model	Interactive image
KEGG	D03186 Y
MeSH	butane
PubChem	7843
RTECS number	EJ4200000
UNII	6LV4FOR43R Y
UN number	1011
InChI InChI=1S/C4H10/c1-3-4-2/h3-4H2,1-2H3 Y Key: IJDNQMDRQITEOD-UHFFFAOYSA-N Y
SMILES CCCC
Properties
Chemical formula	C4H10
Molar mass	58.12 g·mol−1
Appearance	Colorless gas
Odor	Gasoline-like or natural gas-like
Density	2.48 kg/m3 (at 15 °C (59 °F))
Melting point	−140 to −134 °C; −220 to −209 °F; 133 to 139 K
Boiling point	−1 to 1 °C; 30 to 34 °F; 272 to 274 K
Solubility in water	61 mg L−1 (at 20 °C (68 °F))
log P	2.745
Vapor pressure	~170 kPa at 283 K
Henry's law constant (kH)	11 nmol Pa−1 kg−1
Thermochemistry
Specific heat capacity (C)	98.49 J K−1 mol−1
Std enthalpy of formation (ΔfHo298)	−126.3–−124.9 kJ mol−1
Std enthalpy of combustion (ΔcHo298)	−2.8781–−2.8769 MJ mol−1
Vapor pressure	{{{value}}}
Related compounds
Related alkanes	Propane Isobutane Pentane
Related compounds	Perfluorobutane
Supplementary data page
Structure and properties	Refractive index (n), Dielectric constant (εr), etc.
Thermodynamic data	Phase behaviour solid–liquid–gas
Spectral data	UV, IR, NMR, MS
Y verify (what is YN ?)
Infobox references

Butane (/ˈbjuːteɪn/) is an organic compound with the formula C₄H₁₀ that is an alkane with four carbon atoms. Butane is a gas at room temperature and atmospheric pressure. The term may refer to either of two structural isomers, n-butane or isobutane (or "methylpropane"), or to a mixture of these isomers. In the IUPAC nomenclature, however, "butane" refers only to the n-butane isomer (which is the isomer with the unbranched structure). Butanes are highly flammable, colorless, easily liquefied gases. The name butane comes from the roots but- (from butyric acid) and -ane.

Isomers

Common name	normal butane unbranched butane n-butane	isobutane i-butane
IUPAC name	butane	2-methylpropane
Molecular diagram
Skeletal diagram

Rotation about the central C−C bond produces two different conformations (trans and gauche) for n-butane.

Reactions

Spectrum of the blue flame from a butane torch showing CH molecular radical band emission and C₂ Swan bands

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.

When there is sufficient oxygen:

2 C₄H₁₀ + 13 O₂ → 8 CO₂ + 10 H₂O

When oxygen is limited:

2 C₄H₁₀ + 9 O₂ → 8 CO + 10 H₂O

The maximum adiabatic flame temperature of butane with air is 2,243 K (1,970 °C; 3,578 °F).

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

2 CH₃CH₂CH₂CH₃ + 7 O₂ → 2 C₂H₂(CO)₂O + 8 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.

Uses

Normal butane can be used for gasoline blending, as a fuel gas, either alone or in a mixture with propane, and as a feedstock for the manufacture of ethylene and butadiene, a key ingredient of synthetic rubber. Isobutane is primarily used by refineries to enhance (increase) the octane number of motor gasoline.

When blended with propane and other hydrocarbons, it may be referred to commercially as LPG, for liquefied petroleum gas. It is 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 such as deodorants.

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 system operating pressure for butane is lower than for the halomethanes, such as R-12, so R-12 systems such as in automotive air conditioning systems, when converted to butane will not function optimally.

Butane cylinder for use in a camping stove.

Butane is also used as lighter fuel for a common lighter or butane torch and is sold bottled as a fuel for cooking and camping. In this form it is often mixed with small amounts of hydrogen sulfide and mercaptans which will give the unburned gas an offensive smell easily detected by the human nose. In this way, butane leaks can easily be identified. Both hydrogen sulfide and mercaptans, while considered poisons, have low boiling points and quickly vaporize when not under pressure. Most commercially available butane also contains a certain amount of contaminant oil which can be removed through filtration but which will otherwise leave a deposit at the point of ignition and may eventually block the uniform flow of gas.

Cordless hair irons are usually powered by butane cartridges.

Effects and health issues

Inhalation of butane can cause euphoria, drowsiness, narcosis, asphyxia, cardiac arrhythmia, fluctuations in blood pressure and temporary memory loss, when abused directly from a highly pressurized container, and can result in death from asphyxiation and ventricular fibrillation. Butane is the most commonly misused volatile substance 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 (−4 °F) 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.

A small amount of nitrogen dioxide, a toxic gas, results from burning butane gas, along with any combustion in the earth's atmosphere, and represents a human health hazard from home heaters and stoves.

See also

• Isobutane
• Dimethyl ether
• Volatile substance abuse
• Butane (data page)
• Butanone
• n-Butanol
• Liquefied petroleum gas
• Industrial gas
• Butane torch

External links

• International Chemical Safety Card 0232
• NIOSH Pocket Guide to Chemical Hazards