Isobutane, also known as i-butane, 2-methylpropane or methylpropane, is a chemical compound with molecular formula HC(CH3)3. It is an isomer of butane. Isobutane is a colorless, odorless gas. It is the simplest alkane with a tertiary carbon atom. Isobutane is used as a precursor molecule in the petrochemical industry, for example in the synthesis of isooctane.
| |||
| |||
| Names | |||
|---|---|---|---|
| Preferred IUPAC name 2-Methylpropane | |||
Other names
| |||
| Identifiers | |||
CAS Number |
| ||
3D model (JSmol) |
| ||
Beilstein Reference | 1730720 | ||
| ChEBI |
| ||
| ChemSpider |
| ||
| ECHA InfoCard | 100.000.780 | ||
| EC Number |
| ||
| E number | E943b (glazing agents, ...) | ||
Gmelin Reference | 1301 | ||
| KEGG |
| ||
PubChem CID |
| ||
| RTECS number |
| ||
| UNII |
| ||
| UN number | 1969 | ||
CompTox Dashboard (EPA) |
| ||
InChI
| |||
SMILES
| |||
| Properties | |||
| C4H10 | |||
| Molar mass | 58.124 g·mol−1 | ||
| Appearance | Colorless gas | ||
| Odor | Odorless | ||
| Density |
| ||
| Melting point | −159.42 °C (−254.96 °F; 113.73 K) | ||
| Boiling point | −11.7 °C (10.9 °F; 261.4 K) | ||
Solubility in water | 48.9 mg⋅L−1 (at 25 °C (77 °F)) | ||
| Vapor pressure | 3.1 atm (310 kPa) (at 21 °C (294 K; 70 °F)) | ||
Henry's law constant (kH) | 8.6 nmol⋅Pa−1⋅kg−1 | ||
| Conjugate acid | |||
Magnetic susceptibility (χ) | −51.7·10−6 cm3/mol | ||
| Thermochemistry | |||
Heat capacity (C) | 96.65 J⋅K−1⋅mol−1 | ||
Std enthalpy of formation (ΔfH⦵298) | −134.8 – −133.6 kJ⋅mol−1 | ||
Std enthalpy of combustion (ΔcH⦵298) | −2.86959 – −2.86841 MJ⋅mol−1 | ||
| Hazards | |||
| GHS labelling: | |||
Pictograms |  | ||
Signal word | Danger | ||
Hazard statements | H220 | ||
Precautionary statements | P210 | ||
| NFPA 704 (fire diamond) | |||
| Flash point | −83 °C (−117 °F; 190 K) | ||
Autoignition temperature | 460 °C (860 °F; 733 K) | ||
| Explosive limits | 1.4–8.3% | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) | None | ||
REL (Recommended) | TWA 800 ppm (1900 mg/m3) | ||
IDLH (Immediate danger) | N.D. | ||
| Safety data sheet (SDS) | lindeus.com | ||
| Related compounds | |||
Related alkane | Isopentane | ||
| Supplementary data page | |||
| Isobutane (data page) | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).  verify (what is   ?) Infobox references | |||
Production
Isobutane is obtained by isomerization of butane.
Uses
Isobutane is the principal feedstock in alkylation units of refineries. Using isobutane, gasoline-grade "blendstocks" are generated with high branching for good combustion characteristics. Typical products created with isobutane are 2,4-dimethylpentane and especially 2,2,4-trimethylpentane.
Solvent
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.
Precursor to tert-butyl hydroperoxide
Isobutane is oxidized to tert-butyl hydroperoxide, which is 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).
Miscellaneous uses
Isobutane is also used as a propellant for aerosol spray cans.
Isobutane is used as part of blended fuels, especially common in fuel canisters used for camping.
Refrigerant
Isobutane is used as a refrigerant. Use in refrigerators started in 1993 when Greenpeace presented the Greenfreeze project with the former East German company . 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 (both of these being commonly known by the trademark Freon), R-134a, and other chlorofluorocarbon or hydrofluorocarbon refrigerants in conventional stationary refrigeration and air conditioning systems.
As a refrigerant, isobutane poses a fire and explosion risk in addition to the hazards associated with non-flammable CFC refrigerants. Substitution of this refrigerant for motor vehicle air conditioning systems not originally designed for isobutane is widely prohibited or discouraged.
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.
A leak of isobutane in the refrigerant system of a fridge initiated the 2024 Valencia residential complex fire in Spain, that claimed 10 lives.
Nomenclature
The traditional name isobutane was still retained in the 1993 IUPAC recommendations, but is no longer recommended according to the 2013 recommendations. Since the longest continuous chain in isobutane contains only three carbon atoms, the preferred IUPAC name is 2-methylpropane but the locant (2-) is typically omitted in general nomenclature 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.
References
- Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 652. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
The names 'isobutane', 'isopentane', and 'neopentane' are no longer recommended.
- "Solubility in Water". PubChem. National Center for Biotechnology Information. Retrieved 6 April 2017.
- "CDC - NIOSH Pocket Guide to Chemical Hazards - Isobutane". CDC - NIOSH Pocket Guide to Chemical Hazards. CDC. Retrieved 28 December 2018.
- Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health
- NIOSH Pocket Guide to Chemical Hazards. "#0350". National Institute for Occupational Safety and Health (NIOSH).
- "Patent Watch, July 31, 2006". Archived from the original on March 11, 2007. Retrieved August 8, 2006.
- Bipin V. Vora; Joseph A. Kocal; Paul T. Barger; Robert J. Schmidt; James A. Johnson (2003). "Alkylation". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.0112112508011313.a01.pub2. ISBN 0471238961.
- Kenneth S. Whiteley. "Polyethylene". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a21_487.pub2. ISBN 978-3-527-30673-2.
- Rietveld, Will (2005-02-08). "Frequently Asked Questions About Lightweight Canister Stoves and Fuels". Backpacking Light (subscription required). Retrieved 2022-06-03.
- "Technical Meeting on HCFC Phase-Out: Overview of Advantages and Disadvantages of Alternatives (Montreal, Canada; European Commission on retrofit refrigerants for stationary applications)" (PDF). April 2008. Archived (PDF) from the original on 2009-08-05. Retrieved 2021-05-21.
- "GreenFreeze". Greenpeace. 2010-03-15. Archived from the original on 2010-10-05. Retrieved 2013-01-02.
- Wolfgang Lohbeck (June 2004). "Greenfreeze: from a snowball to an industrial avalanche" (PDF). Retrieved 2021-05-21.
- "U.S. EPA hydrocarbon-refrigerants FAQ". Epa.gov. Retrieved 2010-10-29.
- "Compendium of hydrocarbon-refrigerant policy statements, October 2006" (PDF). Archived from the original (PDF) on 2014-08-08. Retrieved 2014-08-01.
- "MACS bulletin: hydrocarbon refrigerant usage in vehicles" (PDF). Archived from the original (PDF) on 2011-01-05. Retrieved 2010-10-29.
- "Society of Automotive Engineers hydrocarbon refrigerant bulletin". Sae.org. 2005-04-27. Archived from the original on 2005-05-05. Retrieved 2010-10-29.
- "Saskatchewan Labour bulletin on hydrocarbon refrigerants in vehicles". Labour.gov.sk.ca. 2010-06-29. Archived from the original on 2009-07-01. 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. Archived from the original (PDF) on 2008-12-17. Retrieved 2010-10-29.
- "New South Wales (Australia) Parliamentary record, 16 October 1997". Parliament.nsw.gov.au. 1997-10-16. Archived from the original on 1 July 2009. Retrieved 2010-10-29.
- "New South Wales (Australia) Parliamentary record, 29 June 2000". Parliament.nsw.gov.au. Archived from the original on 22 May 2005. Retrieved 2010-10-29.
- Domínguez, Teresa (3 May 2024). "Una fuga del gas refrigerante de la nevera del piso 86 propició el inicio del incendio de Campanar". Levante-EMV (in European Spanish). Retrieved 15 October 2024.
- Panico, R. & Powell, W. H., eds. (1994). A Guide to IUPAC Nomenclature of Organic Compounds 1993. Oxford: Blackwell Science. ISBN 0-632-03488-2. https://www.acdlabs.com/iupac/nomenclature/93/r93_679.htm
External links
- International Chemical Safety Card 0901
- NIOSH Pocket Guide to Chemical Hazards
Isobutane also known as i butane 2 methylpropane or methylpropane is a chemical compound with molecular formula HC CH3 3 It is an isomer of butane Isobutane is a colorless odorless gas It is the simplest alkane with a tertiary carbon atom Isobutane is used as a precursor molecule in the petrochemical industry for example in the synthesis of isooctane Isobutane Chemical structure of isobutane with all atoms explicitly shown Skeletal formula of isobutaneBall and stick model of isobutane Spacefill model of isobutaneNamesPreferred IUPAC name 2 MethylpropaneOther names IsobutaneR600aIdentifiersCAS Number 75 28 5 Y3D model JSmol Interactive imageBeilstein Reference 1730720ChEBI CHEBI 30363 YChemSpider 6120 YECHA InfoCard 100 000 780EC Number 200 857 2E number E943b glazing agents Gmelin Reference 1301KEGG D04623 NPubChem CID 6360RTECS number TZ4300000UNII BXR49TP611 YUN number 1969CompTox Dashboard EPA DTXSID1026401InChI InChI 1S C4H10 c1 4 2 3 h4H 1 3H3 YKey NNPPMTNAJDCUHE UHFFFAOYSA N YSMILES CC C CPropertiesChemical formula C 4H 10Molar mass 58 124 g mol 1Appearance Colorless gasOdor OdorlessDensity 2 51 kg m3 at 15 C 100 kPa 563 kg m3 at 15 C boiling liquid Melting point 159 42 C 254 96 F 113 73 K Boiling point 11 7 C 10 9 F 261 4 K Solubility in water 48 9 mg L 1 at 25 C 77 F Vapor pressure 3 1 atm 310 kPa at 21 C 294 K 70 F Henry s law constant kH 8 6 nmol Pa 1 kg 1Conjugate acidMagnetic susceptibility x 51 7 10 6 cm3 molThermochemistryHeat capacity C 96 65 J K 1 mol 1Std enthalpy of formation DfH 298 134 8 133 6 kJ mol 1Std enthalpy of combustion DcH 298 2 86959 2 86841 MJ mol 1HazardsGHS labelling PictogramsSignal word DangerHazard statements H220Precautionary statements P210NFPA 704 fire diamond 140Flash point 83 C 117 F 190 K Autoignition temperature 460 C 860 F 733 K Explosive limits 1 4 8 3 NIOSH US health exposure limits PEL Permissible NoneREL Recommended TWA 800 ppm 1900 mg m3 IDLH Immediate danger N D Safety data sheet SDS lindeus comRelated compoundsRelated alkane IsopentaneSupplementary data pageIsobutane data page Except where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa N verify what is Y N Infobox referencesR600 Isobutane 13 6Kg Cylinder by Starke HvacProductionIsobutane is obtained by isomerization of butane Isomerization of butaneUsesIsobutane is the principal feedstock in alkylation units of refineries Using isobutane gasoline grade blendstocks are generated with high branching for good combustion characteristics Typical products created with isobutane are 2 4 dimethylpentane and especially 2 2 4 trimethylpentane Typical acid catalyzed route to 2 4 dimethylpentane Solvent 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 Precursor to tert butyl hydroperoxide Isobutane is oxidized to tert butyl hydroperoxide which is 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 Miscellaneous uses Isobutane is also used as a propellant for aerosol spray cans Isobutane is used as part of blended fuels especially common in fuel canisters used for camping RefrigerantIsobutane is used as a refrigerant Use in refrigerators started in 1993 when Greenpeace presented the Greenfreeze project with the former East German company de 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 both of these being commonly known by the trademark Freon R 134a and other chlorofluorocarbon or hydrofluorocarbon refrigerants in conventional stationary refrigeration and air conditioning systems As a refrigerant isobutane poses a fire and explosion risk in addition to the hazards associated with non flammable CFC refrigerants Substitution of this refrigerant for motor vehicle air conditioning systems not originally designed for isobutane is widely prohibited or discouraged 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 A leak of isobutane in the refrigerant system of a fridge initiated the 2024 Valencia residential complex fire in Spain that claimed 10 lives NomenclatureThe traditional name isobutane was still retained in the 1993 IUPAC recommendations but is no longer recommended according to the 2013 recommendations Since the longest continuous chain in isobutane contains only three carbon atoms the preferred IUPAC name is 2 methylpropane but the locant 2 is typically omitted in general nomenclature 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 ReferencesNomenclature of Organic Chemistry IUPAC Recommendations and Preferred Names 2013 Blue Book Cambridge The Royal Society of Chemistry 2014 p 652 doi 10 1039 9781849733069 FP001 ISBN 978 0 85404 182 4 The names isobutane isopentane and neopentane are no longer recommended Solubility in Water PubChem National Center for Biotechnology Information Retrieved 6 April 2017 CDC NIOSH Pocket Guide to Chemical Hazards Isobutane CDC NIOSH Pocket Guide to Chemical Hazards CDC Retrieved 28 December 2018 Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health NIOSH Pocket Guide to Chemical Hazards 0350 National Institute for Occupational Safety and Health NIOSH Patent Watch July 31 2006 Archived from the original on March 11 2007 Retrieved August 8 2006 Bipin V Vora Joseph A Kocal Paul T Barger Robert J Schmidt James A Johnson 2003 Alkylation Kirk Othmer Encyclopedia of Chemical Technology doi 10 1002 0471238961 0112112508011313 a01 pub2 ISBN 0471238961 Kenneth S Whiteley Polyethylene Ullmann s Encyclopedia of Industrial Chemistry Weinheim Wiley VCH doi 10 1002 14356007 a21 487 pub2 ISBN 978 3 527 30673 2 Rietveld Will 2005 02 08 Frequently Asked Questions About Lightweight Canister Stoves and Fuels Backpacking Light subscription required Retrieved 2022 06 03 Technical Meeting on HCFC Phase Out Overview of Advantages and Disadvantages of Alternatives Montreal Canada European Commission on retrofit refrigerants for stationary applications PDF April 2008 Archived PDF from the original on 2009 08 05 Retrieved 2021 05 21 GreenFreeze Greenpeace 2010 03 15 Archived from the original on 2010 10 05 Retrieved 2013 01 02 Wolfgang Lohbeck June 2004 Greenfreeze from a snowball to an industrial avalanche PDF Retrieved 2021 05 21 U S EPA hydrocarbon refrigerants FAQ Epa gov Retrieved 2010 10 29 Compendium of hydrocarbon refrigerant policy statements October 2006 PDF Archived from the original PDF on 2014 08 08 Retrieved 2014 08 01 MACS bulletin hydrocarbon refrigerant usage in vehicles PDF Archived from the original PDF on 2011 01 05 Retrieved 2010 10 29 Society of Automotive Engineers hydrocarbon refrigerant bulletin Sae org 2005 04 27 Archived from the original on 2005 05 05 Retrieved 2010 10 29 Saskatchewan Labour bulletin on hydrocarbon refrigerants in vehicles Labour gov sk ca 2010 06 29 Archived from the original on 2009 07 01 Retrieved 2010 10 29 VASA on refrigerant legality amp advisability Archived January 13 2009 at the Wayback Machine Queensland Australia government warning on hydrocarbon refrigerants PDF Energy qld gov au Archived from the original PDF on 2008 12 17 Retrieved 2010 10 29 New South Wales Australia Parliamentary record 16 October 1997 Parliament nsw gov au 1997 10 16 Archived from the original on 1 July 2009 Retrieved 2010 10 29 New South Wales Australia Parliamentary record 29 June 2000 Parliament nsw gov au Archived from the original on 22 May 2005 Retrieved 2010 10 29 Dominguez Teresa 3 May 2024 Una fuga del gas refrigerante de la nevera del piso 86 propicio el inicio del incendio de Campanar Levante EMV in European Spanish Retrieved 15 October 2024 Panico R amp Powell W H eds 1994 A Guide to IUPAC Nomenclature of Organic Compounds 1993 Oxford Blackwell Science ISBN 0 632 03488 2 https www acdlabs com iupac nomenclature 93 r93 679 htmExternal linksInternational Chemical Safety Card 0901 NIOSH Pocket Guide to Chemical Hazards
