Ethane 163106 215115272 2008-05-26T19:48:45Z Benjah-bmm27 126395 [[ball-and-stick model]] of the molecule added {{otheruses4|a chemical compound|the emergency service protocol|ETHANE}} {{Chembox new | Name = Ethane | ImageFileL1 = Ethane-2D.png | ImageSizeL1 = 120px | ImageFileR1 = Ethane-A-3D-balls.png | ImageSizeR1 = 120px | ImageFile2 = Ethane-3D-vdW.png | ImageSize2 = 150px | IUPACName = Ethane | OtherNames = dimethyl; ethyl hydride; methylmethane | Section1 = {{Chembox Identifiers | SMILES = CC | CASNo = 74-84-0 | RTECS = KH3800000 }} | Section2 = {{Chembox Properties | Formula = C<sub>2</sub>H<sub>6</sub> | MolarMass = 30.07 g/mol | Appearance = colourless gas | Density = 1.212 kg/m³, gas | Solubility = 4.7 g/100 ml (? °C) | MeltingPt = -182.76 °C (90.34 K) | BoilingPt = -88.6 °C (184.5 K) | pKa = 50 }} | Section7 = {{Chembox Hazards | EUClass = Highly flammable ('''F+''') | NFPA-H = 1 | NFPA-F = 4 | NFPA-R = | RPhrases = {{R12}} | SPhrases = {{S2}}, {{S9}}, {{S16}}, {{S33}} | FlashPt = -135 °C }} | Section8 = {{Chembox Related | Function = [[alkane]]s | OtherFunctn = [[Methane]]; [[propane]] }} }} '''Ethane''' is a [[chemical compound]] with [[chemical formula]] C<sub>2</sub>H<sub>6</sub>. It is the only two-carbon [[alkane]], that is, an [[aliphatic]] [[hydrocarbon]]. At [[standard temperature and pressure]], ethane is a colorless, odorless [[gas]]. Ethane is isolated on an industrial scale from [[natural gas]], and as a byproduct of [[oil refinery|petroleum refining]]. Its chief use is as [[petrochemical]] feedstock for [[ethylene]] production. ==History== Ethane was first prepared synthetically in 1834 by [[Michael Faraday]], applying [[electrolysis]] of a [[potassium acetate]] solution. He mistook the hydrocarbon product of this reaction for [[methane]], and did not investigate it further.{{inote|Faraday (1834)}} During the period 1847&ndash;1849, in an effort to vindicate the [[radical theory]] of [[organic chemistry]], [[Hermann Kolbe]] and [[Edward Frankland]] produced ethane by the reductions of [[propionitrile]] (ethyl cyanide) {{inote|Kolbe & Frankland (1849)}} and [[ethyl iodide]] {{inote|Frankland (1850)}} with [[potassium]] metal, and, as did Faraday, by the electrolysis of aqueous acetates. They, however, mistook the product of these reactions for [[methyl]] radical, rather than the [[dimer]] of methyl, ethane. This error was corrected in 1864 by [[Carl Schorlemmer]], who showed that the product of all these reactions was in fact ethane. Its name was made from the name of [[ether]], which at first meant [[diethyl ether]]. ==Chemistry== In the laboratory, ethane may be conveniently prepared by [[Kolbe electrolysis]]. In this technique, an aqueous solution of an [[acetate]] salt is [[electrolysis|electrolysed]]. At the [[anode]], acetate is oxidized to produce [[carbon dioxide]] and [[methyl]] radicals, and the highly reactive methyl radicals combine to produce ethane: : [[acetate|CH<sub>3</sub>COO<sup>−</sup>]] → CH<sub>3</sub>• + [[carbon dioxide|CO<sub>2</sub>]] + [[electron|e<sup>−</sup>]] : CH<sub>3</sub>• + •CH<sub>3</sub> → C<sub>2</sub>H<sub>6</sub> Another method, the oxidation of [[acetic anhydride]] by [[peroxide]]s, is conceptually similar. The chemistry of ethane also involves chiefly [[free radical reaction]]s. Ethane can react with the [[halogen]]s, especially [[chlorine]] and [[bromine]], by [[free radical halogenation]]. This reaction proceeds through the propagation of the [[ethyl]] radical: : C<sub>2</sub>H<sub>5</sub>• + [[chlorine|Cl<sub>2</sub>]] → [[ethyl chloride|C<sub>2</sub>H<sub>5</sub>Cl]] + Cl• : Cl• + C<sub>2</sub>H<sub>6</sub> → C<sub>2</sub>H<sub>5</sub>• + [[hydrochloric acid|HCl]] Because halogenated ethanes can undergo further free radical halogenation, this process results in a mixture of several halogenated products. In the chemical industry, more selective chemical reactions are used for the production of any particular two-carbon halocarbon. ===Combustion=== The complete [[combustion]] of ethane releases 1561 kJ/mol, or 51.9 kJ/g, of heat, and produces [[carbon dioxide]] and [[water]] according to the [[chemical equation]] : 2 C<sub>2</sub>H<sub>6</sub> + 7 [[oxygen|O<sub>2</sub>]] → 4 [[carbon dioxide|CO<sub>2</sub>]] + 6 [[water|H<sub>2</sub>O]] + 3122 kJ/mol Combustion occurs by a complex series of free-radical reactions. [[Computer simulation]]s of the [[chemical kinetics]] of ethane combustion have included hundreds of reactions. An important series of reaction in ethane combustion is the combination of an ethyl radical with [[oxygen]], and the subsequent breakup of the resulting [[peroxide]] into ethoxy and hydroxyl radicals. : C<sub>2</sub>H<sub>5</sub>• + [[oxygen|O<sub>2</sub>]] → C<sub>2</sub>H<sub>5</sub>OO• : C<sub>2</sub>H<sub>5</sub>OO• + HR → C<sub>2</sub>H<sub>5</sub>OOH + [[free radical|•R]] : C<sub>2</sub>H<sub>5</sub>OOH → C<sub>2</sub>H<sub>5</sub>O• + •OH The principal carbon-containing products of incomplete ethane combustion are single-carbon compounds such as [[carbon monoxide]] and [[formaldehyde]]. One important route by which the carbon-carbon bond in ethane is broken to yield these single-carbon products is the decomposition of the ethoxy radical into a [[methyl]] radical and formaldehyde, which can in turn undergo further oxidation. : C<sub>2</sub>H<sub>5</sub>O• → CH<sub>3</sub>• + [[formaldehyde|CH<sub>2</sub>O]] Some minor products in the incomplete combustion of ethane include [[acetaldehyde]], [[methane]], [[methanol]], and [[ethanol]]. At higher temperatures, especially in the range 600&ndash;900 °C, [[ethylene]] is a significant product. It arises via reactions like : C<sub>2</sub>H<sub>5</sub>• + [[oxygen|O<sub>2</sub>]] → [[ethylene|C<sub>2</sub>H<sub>4</sub>]] + •OOH Similar reactions (although with species other than oxygen as the hydrogen abstractor) are involved in the production of ethylene from ethane in [[steam cracking]]. ==Production== After [[methane]], ethane is the second-largest component of [[natural gas]]. Natural gas from different gas fields varies in ethane content from less than 1% to over 6% by volume. Prior to the 1960s, ethane and larger molecules were typically not separated from the methane component of natural gas, but simply burnt along with the methane as a fuel. Today, however, ethane is an important [[petrochemical]] feedstock, and it is separated from the other components of natural gas in most well-developed gas fields. Ethane can also be separated from [[petroleum gas]], a mixture of gaseous hydrocarbons that arises as a byproduct of [[petroleum refining]]. Economics of building and running processing plants can change, however. If the relative value of sending the unprocessed natural gas to a consumer exceeds the value of extracting ethane, then the plant may not be run. This can cause operational issues managing the changing quality of the gas in downstream systems.[http://www.aga.org/Content/ContentGroups/Advocacy1/Regulation1/FERC1/commentsinter.pdf] Ethane is most efficiently separated from methane by liquefying it at cryogenic temperatures. Various refrigeration strategies exist: the most economical process presently in wide use employs turboexpansion, and can recover over 90% of the ethane in natural gas. In this process, chilled gas expands through a [[turbine]]; as it expands, its temperature drops to about -100 °C. At this low temperature, gaseous methane can be separated from the liquefied ethane and heavier hydrocarbons by [[distillation]]. Further distillation then separates ethane from the [[propane]] and heavier hydrocarbons. ==Uses== The chief use of ethane is in the chemical industry (usually uses a catalyst to boost up the reaction), in the production of [[ethylene]] by [[steam cracking]]. When diluted with steam and briefly heated to very high temperatures (900 °C or more), heavy hydrocarbons break down into lighter hydrocarbons, and [[saturated hydrocarbon]]s become [[unsaturated (hydrocarbon)|unsaturated]]. Ethane is favored for ethylene production because the steam cracking of ethane is fairly selective for ethylene, while the steam cracking of heavier hydrocarbons yields a product mixture poorer in ethylene, and richer in heavier [[olefin]]s such as [[propylene]] and [[butadiene]], and in [[aromatic hydrocarbon]]s. Experimentally, ethane is under investigation as a feedstock for other commodity chemicals. Oxidative chlorination of ethane has long appeared to be a potentially more economical route to [[vinyl chloride]] than ethylene chlorination. Many processes for carrying out this reaction have been [[patent]]ed, but poor selectivity for vinyl chloride and corrosive reaction conditions (specifically, a [[hydrochloric acid]]-containing reaction mixture at temperatures greater than 500 °C) have discouraged the commercialization of most of them. Presently, [[INEOS]] operates a 1000 t/a ethane-to-vinyl chloride pilot plant at [[Wilhemshaven]] in [[Germany]]. Similarly, the [[Saudi Arabia]]n firm [[SABIC]] has announced construction of a 30,000 t/a plant to produce [[acetic acid]] by ethane oxidation at [[Yanbu]]. This economic viability of this process may rely on the low cost of ethane near Saudi oil fields, and it may not be competitive with [[methanol carbonylation]] elsewhere in the world. Ethane can be used as a refrigerant in cryogenic refrigeration systems. On a much smaller scale, in scientific research, liquid ethane is used to [[vitrification|vitrify]] water-rich samples for [[electron microscopy]]. A thin film of water, quickly immersed in liquid ethane at -150 °C or colder, freezes too quickly for water to crystallize. This rapid freezing does not disrupt the structure of [[soft materials|soft objects]] present in the liquid state, as the formation of [[ice]] crystals can do. ==Health and safety== At room temperature, ethane is a flammable gas. When mixed with air at 3.0% &ndash; 12.5% by volume, it forms an [[explosion|explosive]] mixture. Some additional precautions are necessary where ethane is stored as a cryogenic liquid. Direct contact with liquid ethane can result in severe [[frostbite]]. In addition, the vapors evaporating from liquid ethane are, until they warm to room temperature, heavier than air and can creep along the ground or gather in low places, and if they encounter an ignition source, can flash back to the body of ethane from which they evaporated. Containers recently emptied of ethane may contain insufficient [[oxygen]] to support life. Beyond this [[asphyxiation]] hazard, ethane poses no known acute or chronic toxicological risk. It is not known or suspected to be a [[carcinogen]]. ==Atmospheric and extraterrestrial ethane== [[Image:Titan North Pole Lakes PIA08630.jpg|right|thumb|250px|A photograph of [[Titan (moon)|Titan]]'s northern latitudes. The dark features appear to be hydrocarbon lakes, but further images will be needed to see if the dark spots remain the same (as they would if they were lakes)]] Ethane occurs as a trace gas in the [[Earth's atmosphere]], having a concentration at [[sea level]] of around 0.5 [[parts per billion|ppbv]]<ref>[http://www.atmosphere.mpg.de/enid/3tg.html Trace gases]</ref> at present, though its pre-industrial concentration is likely to have been substantially less as a large proportion of the ethane in today's atmosphere probably originated as unburned [[fossil fuel]]s. Although ethane is a [[greenhouse gas]], it is much less abundant than methane and also less efficient relative to mass. It has also been detected as a trace component in the atmospheres of all four [[giant planet]]s, and in the atmosphere of [[Saturn (planet)|Saturn]]'s moon [[Titan (moon)|Titan]]. Atmospheric ethane results from the Sun's [[photochemistry|photochemical]] action on methane gas, also present in these atmospheres: [[ultraviolet]] photons of shorter [[wavelength]]s than 160 [[nanometer|nm]] can photo-dissociate the methane molecule into a [[methyl]] radical and a [[hydrogen]] atom. When two methyl radicals recombine, the result is ethane: : [[methane|CH<sub>4</sub>]] → CH<sub>3</sub>• + •H : CH<sub>3</sub>• + •CH<sub>3</sub> → C<sub>2</sub>H<sub>6</sub> In the case of Titan, it was once widely hypothesized that ethane produced in this fashion rained back onto the moon's surface, and over time had accumulated into hydrocarbon seas or oceans covering much of the moon's surface. Infrared telescopic observations cast significant doubt on this hypothesis, and the [[Huygens probe]], which landed on Titan in 2005, failed to observe any surface liquids, although it did photograph features that could be presently dry drainage channels. The Cassini probe though has found evidence of lakes at the poles of Titan, where it is hypothesised, that it is cold enough for methane and ethane to liquify. In 1996, ethane was detected in [[Comet Hyakutake]],{{inote|Mumma (1996)}} and it has since been detected in some other [[comets]]. The existence of ethane in these distant solar system bodies may implicate ethane as a primordial component of the [[solar nebula]] from which the sun and planets are believed to have formed. ==References== <references/> * Michael Faraday (1834). Experimental researches in electricity: Seventh series. ''Philosophical Transactions'', 124:77&ndash;122. * Hermann Kolbe, Edward Frankland (1849). On the products of the action of potassium on cyanide of ethyl. ''Journal of the Chemical Society'', 1:60&ndash;74. * Edward Frankland (1850). On the isolation of the organic radicals. ''Journal of the Chemical Society'', 2:263&ndash;296. * Hermann Kolbe (1850). Researches on the electrolysis of organic compounds. ''Journal of the Chemical Society'', 2:157&ndash;184. * Carl Schorlemmer (1864). ''Annalen der Chimie'', 132:234. * Michael J. Mumma ''et al.'' (1996). Detection of Abundant Ethane and Methane, Along with Carbon Monoxide and Water, in Comet C/1996 B2 Hyakutake: Evidence for Interstellar Origin. ''Science'', 272:1310&ndash;1314. ==External links== {{commons|Ethane|Ethane}} *[http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc02/icsc0266.htm International Chemical Safety Card 0266] * [http://www.compchemwiki.org/index.php?title=Ethane Computational Chemistry Wiki] * [http://www.bluerhinos.co.uk/molview/indv.php?id=8 Molview from bluerhinos.co.uk See Ethane in 3D] * [http://www.aet.com/gtip1.htm Market-Driven Evolution of Gas Processing Technologies for NGLs] * [http://www.google.com/search?hl=en&q=Ethane Extra information on Ethane] * [http://wiki.jmol.org:81/index.php/User:Bduke Staggered and eclipsed ethane] {{alkanes}} [[Category:Alkanes]] [[ar:إيثان]] [[bs:Etan]] [[ca:Età]] [[cs:Ethan]] [[da:Ethan]] [[de:Ethan]] [[et:Etaan]] [[el:Αιθάνιο]] [[es:Etano]] [[eo:Etano]] [[eu:Etano]] [[fr:Éthane]] [[ko:에테인]] [[hr:Etan]] [[id:Etana]] [[it:Etano]] [[he:אתאן]] [[ku:Êtan]] [[la:Ethanum]] [[lv:Etāns]] [[lb:Ethan]] [[lt:Etanas]] [[hu:Etán]] [[nl:Ethaan]] [[ja:エタン]] [[no:Etan]] [[nn:Etan]] [[pl:Etan]] [[pt:Etano]] [[ro:Etan]] [[ru:Этан]] [[simple:Ethane]] [[sk:Etán]] [[sl:Etan]] [[sr:Етан]] [[fi:Etaani]] [[sv:Etan]] [[ta:எத்தேன்]] [[vi:Êtan]] [[uk:Етан]] [[zh:乙烷]]