Butane (/ˈbjuːteɪn/) is analkane with the formula C4H10. Butane exists as two isomers,n-butane with connectivityCH3CH2CH2CH3 and iso-butane with the formula(CH3)3CH. Both isomers are highly flammable, colorless, easilyliquefiedgases that quickly vaporize at room temperature and pressure. Butanes are a trace components ofnatural gases (NG). The other hydrocarbons in NG includepropane,ethane, and especiallymethane, which are more abundant.Liquefied petroleum gas is a mixture of propane and some butanes.[6]
The name butane comes from the rootbut- (frombutyric acid, named after the Greek word forbutter) and the suffix-ane (for organic compounds).
The first synthesis of butane was accidentally achieved by British chemistEdward Frankland[7] in 1849 fromethyl iodide andzinc, but he had not realized that theethyl radical dimerized and misidentified the substance.[8]
It was discovered in crude petroleum in 1864 byEdmund Ronalds, who was the first to describe its properties,[9][10] which he named "hydride ofbutyl",[11] based on the naming for the then-knownbutyric acid, which had been named and described by the French chemistMichel Eugène Chevreul[12] 40 years earlier. Other names arose in the 1860s: "butyl hydride",[13] "hydride of tetryl"[14] and "tetryl hydride",[15] "diethyl" or "ethyl ethylide"[16] and others.August Wilhelm von Hofmann, in his 1866 systemic nomenclature, proposed the name "quartane",[2] and the modern name was introduced to English from German around 1874.[17]
Butane did not have much practical use until the 1910s, when W. Snelling identified butane and propane as components in gasoline. He found that if they were cooled, they could be stored in a volume-reduced liquified state in pressurized containers. In 1911, Snelling's liquified petroleum gas was publicly available, and his process for producing the mixture was patented in 1913.[18] Butane is one of the most produced industrial chemicals in the 21st century, with around 80-90 billionlbs (40 million US tons, 36 millionmetric tons) produced by theUnited States every year.[19]
The density of butane is highly dependent on temperature and pressure in the reservoir.[20] For example, the density of liquid butane is 571.8±1 kg/m3 (for pressures up to 2 MPa and temperature 27±0.2 °C), while the density of liquid butane is 625.5±0.7 kg/m3 (for pressures up to 2 MPa and temperature −13±0.2 °C).
By weight, butane contains about 49.5 MJ/kg (13.8 kWh/kg; 22.5 MJ/lb; 21,300 Btu/lb) or by liquid volume 29.7megajoules perliter (8.3 kWh/L; 112 MJ/U.S. gal; 107,000 Btu/U.S. gal).
The maximumadiabatic flame temperature of butane with air is 2,243 K (1,970 °C; 3,578 °F).
n-Butane is the feedstock forDuPont's catalytic process for the preparation ofmaleic anhydride:
2 CH3CH2CH2CH3 + 7 O2 → 2 C2H2(CO)2O + 8 H2O
n-Butane, like allhydrocarbons, undergoesfree radical chlorination providing both 1-chloro- and 2-chlorobutanes, as well as more highly chlorinated derivatives. The relative rates of the chlorinations are partially explained by the differingbond dissociation energies: 425 and 411kJ/mol for the two types of C-H bonds.
For gasoline blending, n-butane is the main component used to manipulate theReid vapor pressure (RVP). Since winter fuels require much higher vapor pressure for engines to start, refineries raise the RVP by blending more butane into the fuel.[26] n-Butane has a relatively highresearch octane number (RON) andmotor octane number (MON), which are 93 and 92 respectively.[27]
Pure forms of butane, especially isobutane, are used asrefrigerants and have largely replaced theozone-layer-depletinghalomethanes in refrigerators, freezers, and air conditioning systems. The operating pressure for butane is lower than operating pressures for halomethanes such asFreon-12 (R-12). Hence, R-12 systems, such as those in automotive air conditioning systems, when converted to pure butane, will function poorly. Instead, a mixture of isobutane and propane is used to give cooling system performance comparable to R-12.[29]
Butane is also used as lighter fuel for commonlighters orbutane torches, and is sold bottled as a fuel for cooking, barbecues and camping stoves. In the 20th century, theBraun company ofGermany made a cordless hair styling device product that used butane as its heat source to producesteam.[30]
As fuel, butane is often mixed with small amounts ofmercaptans to give the unburned gas an offensive smell easily detected by the human nose. In this way, butane leaks can easily be identified. Whilehydrogen sulfide and mercaptans are toxic, they are present in levels so low thatsuffocation andfire hazard by the butane becomes a concern far beforetoxicity.[31][32] Most commercially available butane also contains some contaminant oil, which can be removed by filtration. If not removed, it will otherwise leave a deposit at the point of ignition and may eventually block the uniform flow of gas.[33]
The butane used as a solvent for fragrance extraction does not contain these contaminants.[34] Butane gas can causegas explosions in poorly ventilated areas if leaks go unnoticed and are ignited by spark or flame.[5] Purified butane is used as a solvent in the industrial extraction of cannabis oils.
Butane fuel canisters for use in camping stoves
Butane lighter, showing liquid butane reservoir
An aerosol spray can, which may be using butane as a propellant
Table from the 2010 ISCD study ranking various drugs (legal and illegal) based on statements by drug-harm experts. Butane was found to be the 14th overall most dangerous drug.[35]
Inhalation of butane can causeeuphoria,drowsiness,unconsciousness,asphyxia,cardiac arrhythmia, fluctuations in blood pressure and temporary memory loss, when abused directly from a highly pressurized container, and can result in death fromasphyxiation andventricular fibrillation. Butane enters the blood supply, and within seconds, leads to intoxication.[36] Butane is the most commonly abusedvolatile substance in the UK, and was the cause of 52% of solvent related deaths in 2000.[37] By spraying butane directly into the throat, the jet of fluid can cool rapidly to −20 °C (−4 °F) by expansion, causing prolongedlaryngospasm.[38]"Sudden sniffer's death" syndrome, first described by Bass in 1970,[39] is the most common single cause of solvent related deaths, resulting in 55% of known fatal cases.[38]
^ab"General Principles, Rules, and Conventions".Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge:The Royal Society of Chemistry. 2014. P-12.1.doi:10.1039/9781849733069-00001.ISBN978-0-85404-182-4.Similarly, the retained names 'ethane', 'propane', and 'butane' were never replaced by systematic names 'dicarbane', 'tricarbane', and 'tetracarbane' as recommended for analogues of silane, 'disilane'; phosphane, 'triphosphane'; and sulfane, 'tetrasulfane'.
^W. B. Kay (1940). "Pressure-Volume-Temperature Relations for n-Butane".Industrial & Engineering Chemistry.32 (3):358–360.doi:10.1021/ie50363a016.
^Maybery, C. F. (1896). "On the Composition of the Ohio and Canadian Sulphur Petroleums".Proceedings of the American Academy of Arts and Sciences.31:1–66.doi:10.2307/20020618.JSTOR20020618.
^Chevreul (1817)"Extrait d'une lettre de M. Chevreul à MM. les Rédacteurs du Journal de Pharmacie" (Extract of a letter from Mr. Chevreul to the editors of the Journal of Pharmacy),Journal de Pharmacie et des sciences accessoires,3 : 79–81. On p. 81, he named butyric acid:"Ce principe, que j'ai appelé depuis acid butérique, … " (This principle [i.e., constituent], which I have since named "butyric acid", … )
^Committee on Acute Exposure Guideline Levels; Committee on Toxicology; Board on Environmental Studies and Toxicology; Division on Earth and Life Studies; National Research Council (26 September 2013).2. Methyl Mercaptan Acute Exposure Guideline Levels. National Academies Press (US) – via NCBI Bookshelf.
^"BHO Mystery Oil".Skunk Pharm Research. 26 August 2013. Retrieved5 December 2019.
^"Final Report of the Safety Assessment of Isobutane, Isopentane, n-Butane, and Propane".Journal of the American College of Toxicology.1 (4). SAGE Publications:127–142. 1982.doi:10.3109/10915818209021266.ISSN0730-0913.S2CID208503534.
