Butane

Butane
IUPAC name Butane[1]
Identifiers
CAS number	Y
PubChem
ChemSpider	Y
UNII	Y
EC number
UN number	1011
KEGG	Y
MeSH
ChEBI	Y
ChEMBL	Y
RTECS number	EJ4200000
Beilstein Reference	969129
Gmelin Reference	1148
Jmol-3D images	Image 1
SMILES CCCC
InChI InChI=1S/C4H10/c1-3-4-2/h3-4H2,1-2H3 Y Key: IJDNQMDRQITEOD-UHFFFAOYSA-N Y
Properties
Molecular formula	C4H10
Molar mass	58.12 g mol−1
Appearance	Colorless gas
Odor	Odorless
Density	2.48 kg/m3 (at 15 °C)
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)
log P	2.745
Vapor pressure	~25 PSI (at 50 °F) [2]
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
Hazards[3]
MSDS	External MSDS
GHS pictograms
GHS signal word	DANGER
GHS hazard statements	H220
GHS precautionary statements	P210
EU Index	601-004-00-0
EU classification	F+
R-phrases	R12
S-phrases	(S2) S16
NFPA 704	4 1 0
Flash point	−60 °C (−76 °F; 213 K)
Explosive limits	1.8–8.4%
Related compounds
Related alkanes	Propane Isobutane Pentane
Related compounds	Perfluorobutane
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 (77 °F), 100 kPa)
Y   Y/N?)

Butane () is an 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.^[4]

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 is mainly 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.^[5][6][7][8]

When blended with propane and other hydrocarbons, it may be referred to commercially as LPG, for liquified 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.^[9]

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 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.^[10]

Effects and health issues

Inhalation of butane can cause euphoria, drowsiness, narcosis, asphyxia, cardiac arrhythmia, fluctuations in blood pressure, temporary memory loss and frostbite, 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.^[11] By spraying butane directly into the throat, the jet of fluid can cool rapidly to −20 °C by expansion, causing prolonged laryngospasm.^[12] "Sudden sniffer's death" syndrome, first described by Bass in 1970,^[13] is the most common single cause of "solvent related" death, resulting in 55% of known fatal cases.^[12]

A small amount of nitrogen dioxide, a toxic gas, results from burning butane gas, along with any combustion in the earths atmosphere, and represents a human health hazard from home heaters and stoves.^[14]

See also

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

References

External links

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