|Jmol interactive 3D||Image|
|Molar mass||58.12 g·mol−1|
|Density||2.51 mg mL−1 (at 15 °C, 100 kPa)|
|Melting point||−233.2 to −33.1 °C; −387.7 to −27.7 °F; 40.0 to 240.0 K|
|Boiling point||−13 to −9 °C; 8 to 16 °F; 260 to 264 K|
|Vapor pressure||204.8 kPa (at 21 °C (70 °F))|
|8.6 nmol Pa−1 kg−1|
|96.65 J K−1 mol−1|
Std enthalpy of
|−134.8–−133.6 kJ mol−1|
Std enthalpy of
|−2.86959–−2.86841 MJ mol−1|
|Safety data sheet||See: data page
|GHS signal word||DANGER|
EU classification (DSD)
|Flash point||−83 °C (−117 °F; 190 K)|
|460 °C (860 °F; 733 K)|
|US health exposure limits (NIOSH):|
|TWA 800 ppm (1900 mg/m3)|
IDLH (Immediate danger
|Supplementary data page|
|Refractive index (n),
Dielectric constant (εr), etc.
|UV, IR, NMR, MS|
|what is ?)(|
Isobutane (i-butane), also known as methylpropane, is a chemical compound with molecular formula C
10 and is an isomer of butane. It is the simplest alkane with a tertiary carbon. Concerns with depletion of the ozone layer by freon gases have led to increased use of isobutane as a gas for refrigeration systems, especially in domestic refrigerators and freezers, and as a propellant in aerosol sprays. When used as a refrigerant or a propellant, isobutane is also known as R-600a. Some portable camp stoves use a mixture of isobutane with propane, usually 80:20. Isobutane is used as a feedstock in the petrochemical industry, for example in the synthesis of isooctane.
Isobutane is the trivial name retained by the International Union of Pure and Applied Chemistry (IUPAC) in its 1993 Recommendations for the Nomenclature of Organic Chemistry. Since the longest continuous chain in isobutane contains only three carbon atoms, the full systematic name is 2-methylpropane but the locant (2-) is typically omitted as redundant; C2 is the only position on a propane chain where a methyl substituent can be located without altering the main chain and forming the constitutional isomer n-butane.
Isobutane is used as a refrigerant. The use in refrigerators started in 1993 when Greenpeace presented the Greenfreeze project with the German company Foron. In this regard, blends of pure, dry "isobutane" (R-600a) (that is, isobutane mixtures) have negligible ozone depletion potential and very low Global Warming Potential (having a value of 3.3 times the GWP of carbon dioxide) and can serve as a functional replacement for R-12, R-22, R-134a, and other chlorofluorocarbon or hydrofluorocarbon refrigerants in conventional stationary refrigeration and air conditioning systems.
In the Chevron Phillips slurry process for making high-density polyethylene, isobutane is used as a diluent. As the slurried polyethylene is removed, isobutane is "flashed" off, and condensed, and recycled back into the loop reactor for this purpose.
Isobutane is also used as a propellant for aerosol cans and foam products.
Isobutane is also used as a raw material in the manufacture of propylene oxide, where it is oxidized to tert-butyl hydroperoxide and subsequently reacted with propylene to yield propylene oxide. The tert-butanol that results as a by-product is typically used to make gasoline additives such as methyl tert-butyl ether (MTBE).
As a refrigerant, isobutane has an explosion risk in addition to the hazards associated with non-flammable CFC refrigerants. Reports surfaced in late 2009 suggesting the use of isobutane as a refrigerant in domestic refrigerators was potentially dangerous. Several refrigerator explosions reported in the United Kingdom are suspected to have been caused as a result of isobutane leaking into the refrigerator cabinet and being ignited by sparks in the electrical system. Although unclear how serious this could be, at the time this report came out it was estimated 300 million refrigerators worldwide use isobutane as a refrigerant.
Substitution of this refrigerant for motor vehicle air conditioning systems not originally designed for isobutane is widely prohibited or discouraged, on the grounds that using flammable hydrocarbons in systems originally designed to carry non-flammable refrigerant presents a significant risk of fire or explosion.
Vendors and advocates of hydrocarbon refrigerants argue against such bans on the grounds that there have been very few such incidents relative to the number of vehicle air conditioning systems filled with hydrocarbons.
- "ISOBUTANE - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 16 September 2004. Identification and Related Records. Retrieved 5 March 2012.
- "NIOSH Pocket Guide to Chemical Hazards #0350". National Institute for Occupational Safety and Health (NIOSH).
- Patent Watch, July 31, 2006.
- Panico, R.; & Powell, W. H. (Eds.) (1994). A Guide to IUPAC Nomenclature of Organic Compounds 1993. Oxford: Blackwell Science. ISBN 0-632-03488-2. http://www.acdlabs.com/iupac/nomenclature/93/r93_679.htm
- "European Commission on retrofit refrigerants for stationary applications" (PDF). Retrieved 2010-10-29.
- Page - March 15, 2010 (2010-03-15). "GreenFreeze". Greenpeace. Retrieved 2013-01-02.
- Kenneth S. Whiteley (2005), "Polyethylene", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a21_487.pub2
- Rietveld, Will (2005-02-08). "Frequently Asked Questions About Lightweight Canister Stoves and Fuels". Backpacking Light. Retrieved 2014-07-26.
- Bingham, John (September 1, 2009). "Exploding fridges: ozone friendly gas theory for mystery blasts". The Daily Telegraph (London). Retrieved May 5, 2010.
- "U.S. EPA hydrocarbon-refrigerants FAQ". Epa.gov. Retrieved 2010-10-29.
- Compendium of hydrocarbon-refrigerant policy statements, October 2006
- "MACS bulletin: hydrocarbon refrigerant usage in vehicles" (PDF). Retrieved 2010-10-29.
- "Society of Automotive Engineers hydrocarbon refrigerant bulletin". Sae.org. 2005-04-27. Retrieved 2010-10-29.
- "Saskatchewan Labour bulletin on hydrocarbon refrigerants in vehicles". Labour.gov.sk.ca. 2010-06-29. Retrieved 2010-10-29.
- VASA on refrigerant legality & advisability Archived January 13, 2009 at the Wayback Machine
- "Queensland (Australia) government warning on hydrocarbon refrigerants" (PDF). Energy.qld.gov.au. Retrieved 2010-10-29.
- "New South Wales (Australia) Parliamentary record, 16 October 1997". Parliament.nsw.gov.au. 1997-10-16. Retrieved 2010-10-29.
- "New South Wales (Australia) Parliamentary record, 29 June 2000". Parliament.nsw.gov.au. Retrieved 2010-10-29.