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| Names | |||
|---|---|---|---|
| Preferred IUPAC name 2-Methylpropane[1] | |||
Other names
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| Identifiers | |||
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3D model (JSmol) | |||
| 1730720 | |||
| ChEBI | |||
| ChemSpider |
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| ECHA InfoCard | 100.000.780 | ||
| EC Number |
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| E number | E943b(glazing agents, ...) | ||
| 1301 | |||
| KEGG |
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| RTECS number |
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| UNII | |||
| UN number | 1969 | ||
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| Properties | |||
| C4H10 | |||
| Molar mass | 58.124 g·mol−1 | ||
| Appearance | Colorless gas | ||
| Odor | Odorless | ||
| Density |
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| Melting point | −159.42 °C (−254.96 °F; 113.73 K)[4] | ||
| Boiling point | −11.7 °C (10.9 °F; 261.4 K)[4] | ||
| 48.9 mg⋅L−1 (at 25 °C (77 °F))[2] | |||
| Vapor pressure | 3.1 atm (310 kPa) (at 21 °C (294 K; 70 °F))[3] | ||
Henry's law constant (kH) | 8.6 nmol⋅Pa−1⋅kg−1 | ||
| Conjugate acid | Isobutanium | ||
| −51.7·10−6 cm3/mol | |||
| Thermochemistry | |||
| 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: | |||
 | |||
| Danger | |||
| H220 | |||
| P210 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | −83 °C (−117 °F; 190 K) | ||
| 460 °C (860 °F; 733 K) | |||
| Explosive limits | 1.4–8.3% | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) | None[5] | ||
REL (Recommended) | TWA 800 ppm (1900 mg/m3)[5] | ||
IDLH (Immediate danger) | N.D.[5] | ||
| 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 theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Isobutane, also known asi-butane,2-methylpropane ormethylpropane, is achemical compound withmolecular formula HC(CH3)3. It is anisomer ofbutane. Isobutane is a colorless, odorless gas.It is the simplestalkane with atertiary carbon atom. Isobutane is used as a precursor molecule in thepetrochemical industry, for example in the synthesis ofisooctane.[6]
Isobutane is obtained byisomerization ofbutane.[citation needed]
Isobutane is the principal feedstock inalkylation units of refineries. Using isobutane, gasoline-grade "blendstocks" are generated with high branching for good combustion characteristics. Typical products created with isobutane are2,4-dimethylpentane and especially2,2,4-trimethylpentane.[7]
In the Chevron Phillips slurry process for makinghigh-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.[8]
Isobutane is oxidized totert-butyl hydroperoxide, which is subsequently reacted withpropylene to yieldpropylene oxide. Thetert-butanol that results as a by-product is typically used to make gasoline additives such asmethyl tert-butyl ether (MTBE).
Isobutane is also used as a propellant foraerosol spray cans.
Isobutane is used as part of blended fuels, especially common in fuel canisters used forcamping.[9]
Isobutane is used as arefrigerant.[10] Use in refrigerators started in 1993 whenGreenpeace presented the Greenfreeze project with the former East German companyForon [de].[11][12] In this regard, blends of pure, dry "isobutane" (R-600a) (that is, isobutane mixtures) have negligibleozone depletion potential and very lowglobal warming potential (having a value of 3.3 times the GWP of carbon dioxide) and can serve as a functional replacement forR-12,R-22 (both of these being commonly known by the trademarkFreon),R-134a, and otherchlorofluorocarbon orhydrofluorocarbonrefrigerants 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.[13][14][15][16][17][18][19]
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.[20][21]
A leak of isobutane in the refrigerant system of a fridge initiated the2024 Valencia residential complex fire inSpain, that claimed 10 lives.[22]
The traditional name isobutane was still retained in the 1993IUPAC recommendations,[23] but is no longer recommended according to the 2013 recommendations.[1] Since the longest continuous chain in isobutane contains only three carbon atoms, thepreferred IUPAC name is 2-methylpropane but thelocant (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 isomern-butane.
The names 'isobutane', 'isopentane', and 'neopentane' are no longer recommended.
