View source for Ethylene

{{Chembox
| Watchedfields = changed
| verifiedrevid = 308463104
| ImageFile1 = Ethylene-CRC-MW-dimensions-2D.png
|   ImageSize1 = 150px
| ImageFile2 = Ethylene-CRC-MW-3D-balls.png
|   ImageSize2 = 100px
| ImageFile3 = Ethylene-3D-vdW.png
|   ImageSize3 = 100px
| IUPACName = Ethene
|   OtherNames = 
| Section1 = {{Chembox Identifiers
|   CASNo = 74-85-1
|    CASNo_Ref = {{cascite}}
|   PubChem = 
|   SMILES = C=C
|   InChI=1/C2H4/c1-2/h1-2H2
|   EC-number = 200-815-3
|   ChemSpiderID = 6085
  }}
| Section2 = {{Chembox Properties
|   Formula = C<sub>2</sub>H<sub>4</sub>
|   MolarMass = 28.05 g/mol
|   Appearance = colourless gas
|   Density = 1.178&nbsp;kg/m<sup>3</sup> at 15 °C, gas <ref name="GESTIS">{{GESTIS|ZVG=12710|Name=Ethylene|Date=25 October 2007}}</ref>
|   MeltingPt = &minus;169.2 °C (104.0 K, -272.6 °F)
|   BoilingPt = &minus;103.7 °C (169.5 K, -154.7 °F)
|   Solubility = 3.5&nbsp;mg/100 ml (17 °C)
|   pKa = 44
|   CriticalPt = 282.4 K (9.2 °C)<br/>at 5.04 MPa (50 atm)
  }}
| Section3 = {{Chembox Structure
|   MolShape = D<sub>2h</sub>
|   Dipole = zero
  }}
| Section4 = {{Chembox Thermochemistry
|   DeltaHf = +52.47 kJ/mol
|   DeltaHc = 
|   Entropy = 219.32 J·K<sup>&minus;1</sup>·mol<sup>&minus;1</sup>
|   HeatCapacity = 
  }}
| Section7 = {{Chembox Hazards
|   EUIndex = 
|   EUClass = Extremely flammable ('''F+''')
|   RPhrases = 
|   SPhrases = 
|   NFPA-H = 3
|   NFPA-F = 4
|   NFPA-R = 2
|   NFPA-O = 
|   FlashPt = -136 °C
|   Autoignition = 542.8 °C
  }}
| Section8 = {{Chembox Related
|   OtherFunctn = 
|    Function = 
|   OtherCpds = [[Ethane]]<br/>[[Acetylene]]
  }}
}}
'''Ethylene''' ([[IUPAC]] name: '''ethene''') is a gaseous [[organic compound]] with the formula C<sub>2</sub>H<sub>4</sub>. It is the simplest [[alkene]] (older name: ''olefin'' from its oil-forming property). Because it contains a carbon-carbon double bond, ethylene is classified as an ''unsaturated hydrocarbon.'' Ethylene is widely used in industry and also has a role in biology as a [[hormone]].<ref name=Wang_2002>{{cite journal | author = Wang K, Li H, Ecker J | title = Ethylene biosynthesis and signaling networks | journal = Plant Cell | volume = 14 Suppl | issue = | pages = S131–51 | year = 2002| pmid = 12045274 | pmc = 151252}}</ref> Ethylene is the most produced [[organic compound]] in the world; global production of ethylene exceeded 107 million metric tonnes in 2005.<ref>“Production: Growth is the Norm” Chemical and Engineering News, July 1 0, 2006, p. 59.</ref> To meet the ever increasing demand for ethylene, sharp increases in production facilities have been added globally, particularly in the [[Persian Gulf]] countries.

==Structure and bonding==
This [[hydrocarbon]] has four [[hydrogen]] [[atom]]s bound to a pair of [[carbon]] atoms that are connected by a [[double bond]]. All six atoms that comprise ethylene are [[coplanar]]. The H-C-H [[angle]] is 119°, close to the 120° for ideal sp² [[hybridization (chemistry)|hybridized]] carbon. The molecule is also relatively rigid: rotation about the C-C bond is a high energy process that requires breaking the π-bond.

[[Image:Dewar-Chatt-Duncanson_model.png‎|thumb|260 px|left|Orbital description of bonding between ethylene and a transition metal.]]
The π-bond in the ethylene molecule is responsible for its useful reactivity. The double bond is a region of high [[electron density]], thus it is susceptible to attack by electrophiles. Many reactions of ethylene are catalyzed by transition metals, which bind transiently to the ethylene using both the π and π* orbitals.

==Uses==
Major industrial reactions of ethylene include in order of scale: 1) [[polymerization]], 2) [[oxidation]], 3) [[halogenation]] and [[hydrohalogenation]], 4) [[alkylation]], 5) [[Hydration reaction|hydration]], 6) [[oligomerization]], and 7) [[hydroformylation]]. Ethylene can also be hydrated to give [[ethanol]], but this method is rarely used industrially. In the [[United States]] and [[Europe]], approximately 90% of ethylene is used to produce three chemical compounds—[[ethylene oxide]], [[ethylene dichloride]], and [[ethylbenzene]]—and a variety of kinds of [[polyethylene]].<ref name="inchem">{{cite web|url=http://www.inchem.org/documents/sids/sids/74851.pdf|format=PDF|title=OECD SIDS Initial Assessment Profile - Ethylene|publisher=inchem.org|accessdate=2008-05-21}}</ref>
[[Image:C2H4uses.png|thumb|520 px|center|Main industrial uses of ethylene. Clockwise from the upper right: its conversions to [[ethylene oxide]], precursor to ethylene glycol, to [[ethylbenzene]], precursor to [[styrene]], to various kinds of [[polyethylene]], to [[ethylene dichloride]], precursor to [[vinyl chloride]].]]
===Polymerization===
{{See also|Ziegler-Natta catalyst}}{{See also|Polyethylene}}
Polyethylenes of various types consume more than half of world ethylene supply. Polyethylene, also called ''polythene'', is the world's most widely-used plastic, being primarily used to make films used in [[packaging]], [[carrier bags]] and trash [[liners]]. Linear [[alpha-olefins]], produced by [[oligomerization]] (formation of short polymers) are used as [[precursor (chemistry)|precursors]], [[detergents]], [[plasticisers]], [[synthetic lubricants]], additives, and also as co-monomers in the production of polyethylenes.<ref name="inchem" />

===Oxidation===
Ethylene is [[oxidation|oxidized]] to produce [[ethylene oxide]], a key raw material in the production of [[surfactant]]s and [[detergent]]s by [[ethoxylation]]. Ethylene oxide also hydrolyzed to produce [[ethylene glycol]], widely used as an automotive antifreeze as well as higher molecular weight glycols and [[glycol ethers]].

{{Main|Wacker process}}
Ethylene undergoes oxidation by palladium to give [[acetaldehyde]]. This conversion remains a major industrial process (10M kg/y).<ref>{{cite book|last=Elschenbroich|first=C.|coauthors=Salzer, A.|authorlink=|title=Organometallics : A Concise Introduction|edition=2nd|publisher=Wiley-VCH|location=Weinheim|year=2006|isbn=3-527-28165-7|series=}}</ref> The process proceeds via the initial complexation of ethylene to a Pd(II) center.

===Halogenation and hydrohalogenation===
Major intermediates from the [[halogenation]] and [[hydrohalogenation]] of ethylene include [[ethylene dichloride]], [[ethyl chloride]] and [[ethylene dibromide]]. The addition of chlorine entails "oxychlorination," i.e. chlorine itself is not used. Some products derived from this group are [[polyvinyl chloride]], [[trichloroethylene]], [[perchloroethylene]], [[methyl chloroform]], [[polyvinylidiene chloride]] and [[copolymers]], and [[ethyl bromide]].<ref name=Keystone/>

===Alkylation===
Major chemical intermediates from the [[alkylation]] with ethylene is [[ethylbenzene]], precursor to [[styrene]]. Styrene is used principally in [[polystyrene]] for packaging and insulation, as well as in [[styrene-butadiene]] rubber for tires and footwear. On a smaller scale, ethyl[[toluene]], ethylanilines, 1,4-hexadiene, and [[aluminium]] alkyls. Products of these intermediates include [[polystyrene]], unsaturated [[polyesters]] and ethylene-propylene [[copolymers|terpolymers]].<ref name=Keystone/>

===Oxo-reaction===
The [[hydroformylation]] (oxo-reaction) of ethylene results in [[propionaldehyde]], a precursor to [[propionic acid]] and [[n-propyl alcohol]].<ref name=Keystone/>

===Niche uses===
Given the scale of its production, ethylene is inevitably used in thousands of applications. For example, ethylene is an [[anesthesiology|anesthetic agent]] (in an 85% ethylene/15% oxygen ratio).<ref name=>{{cite journal
|author=Hugh H. Trout
|title=BLOOD CHANGES UNDER ETHYLENE ANESTHESIA
|journal=Annals of Surgery
|volume=86
|issue=2
|pages=260–267
|date=August 1927
|doi=
10.1097/00000658-192708000-00013
|pmc=1399426|pmid=
17865725|pmcid=2452601
|url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1399426/pdf/annsurg00607-0100.pdf
|accessdate=27 July 2010}}</ref> It can also be used to hasten fruit ripening, as well as a welding gas.<ref name="inchem" /><ref name="calibulletin">{{cite journal|date=June 1, 1976|title=Informational Bulletin|publisher=California Fresh Market Advisory Board|volume=12}}</ref>

==Production==
Ethylene is produced in the [[petrochemical]] industry by [[steam cracking]]. In this process, gaseous or light liquid hydrocarbons are heated to 750&ndash;950 °C, inducing numerous [[free radical]] [[chemical reaction|reactions]] followed by immediate [[quench]] to stop these reactions. This process converts large hydrocarbons into smaller ones and introduces unsaturation. Ethylene is separated from the resulting complex mixture by repeated [[Physical compression|compression]] and [[distillation]]. In a related process used in oil refineries, high molecular weight hydrocarbons are cracked over [[zeolite]] catalysts. Heavier feedstocks, such as naphtha and gas oils require at least two "quench towers" downstream of the cracking furnaces to recirculate pyrolysis-derived gasoline and process water. When cracking a mixture of ethane and propane, only one water quench tower is required.<ref name=Keystone>{{Cite book | last=Kniel | first=Ludwig | authorlink= | coauthors=Winter, Olaf; Stork, Karl | title=Ethylene, keystone to the petrochemical industry | year=1980 | publisher=M. Dekker | location=New York | isbn=0-8247-6914-7 | pages=}}</ref>

The areas of an ethylene plant are: 
# steam cracking furnaces:
# primary and secondary heat recovery with quench; 
# a dilution steam recycle system between the furnaces and the quench system; 
# primary compression of the cracked gas (3 stages of compression); 
# hydrogen sulfide and carbon dioxide removal (acid gas removal); 
# secondary compression (1 or 2 stages); 
# drying of the cracked gas; 
# cryogenic treatment; 
# all of the cold cracked gas stream goes to the demethanizer tower. The overhead stream from the demethanizer tower consists of all the hydrogen and methane that was in the cracked gas stream. Cryogenically ({{convert|-250|°F|°C|abbr=on}}) treating this overhead stream separates hydrogen from methane. Methane recovery is critical to the economical operation of an ethylene plant.
# the bottom stream from the demethanizer tower goes to the deethanizer tower. The overhead stream from the deethanizer tower consists of all the C<sub>2,</sub>'s that were in the cracked gas stream. The C<sub>2</sub> stream contains acetylene, which is explosive above 200 kPa (29 psi)<ref>{{cite book
|first=Mikołaj
|last=Korzun
|title=1000 słów o materiałach wybuchowych i wybuchu
|isbn=83-11-07044-X
|year=1986
|location=Warszawa
|publisher=Wydawnictwo Ministerstwa Obrony Narodowej
|oclc=69535236
}}</ref>. If the partial pressure of acetylene is expected to exceed these values, the C<sub>2</sub> stream is partially hydrogenated. The C<sub>2</sub>'s then proceed to a C<sub>2</sub> splitter. The product ethylene is taken from the overhead of the tower and the ethane coming from the bottom of the splitter is recycled to the furnaces to be cracked again; 
# the bottom stream from the de-ethanizer tower goes to the depropanizer tower. The overhead stream from the depropanizer tower consists of all the C<sub>3</sub>'s that were in the cracked gas stream. Before feeding the C<sub>3</sub>'s to the C<sub>3</sub> splitter, the stream is hydrogenated to convert the [[methylacetylene]] and [[propadiene]] ([[allene]]) mix. This stream is then sent to the C<sub>3</sub> splitter. The overhead stream from the C<sub>3</sub> splitter is product propylene and the bottom stream is propane which is sent back to the furnaces for cracking or used as fuel.
# The bottom stream from the depropanizer tower is fed to the debutanizer tower. The overhead stream from the debutanizer is all of the C<sub>4</sub>'s that were in the cracked gas stream. The bottom stream from the debutanizer (light pyrolysis gasoline) consists of everything in the cracked gas stream that is C<sub>5</sub> or heavier.<ref name=Keystone/>

Since ethylene production is energy intensive, much effort has been dedicated to recovering heat from the gas leaving the furnaces. Most of the energy recovered from the cracked gas is used to make high pressure (1200 psig) steam. This steam is in turn used to drive the turbines for compressing cracked gas, the propylene refrigeration compressor, and the ethylene refrigeration compressor. An ethylene plant, once running, does not need to import steam to drive its steam turbines. A typical world scale ethylene plant (about 1.5 billion pounds of ethylene per year) uses a {{convert|45000|hp}} cracked gas compressor, a {{convert|30000|hp}} propylene compressor, and a {{convert|15000|hp}} ethylene compressor.

===Laboratory aspects===
Ethylene can be produced in the laboratory by heating absolute [[ethanol]] with concentrated [[sulfuric acid]].<ref>{{cite book|title=Practical Organic Chemistry (preparation 5)|author=Julius B. Cohen|publisher=Macmillan|year=1930}}</ref> Interestingly for such a useful compound, ethylene is rarely used in [[organic synthesis]] in the laboratory.<ref>Crimmins, M. T.; Kim-Meade, A. S. "Ethylene" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.</ref>

Being a simple molecule, ethylene is spectroscopically simple. Its UV-vis [[Spectroscopy|spectrum]] is still used as a test of theoretical methods.<ref name=NIST_Webbook>{{cite web | title=Ethylene:UV/Visible Spectrum | work=NIST Webbook | url=http://webbook.nist.gov/cgi/cbook.cgi?ID=C74851&Units=SI&Mask=400#UV-Vis-Spec | accessdate=2006-09-27}}</ref>

==Ethylene as a plant hormone==
Ethylene serves as a [[plant hormone|hormone]] in [[plant]]s.<ref name=Lin>Lin, Z.; Zhong, S. and Grierson, D., "Recent advances in ethylene research", J. Exp. Bot., 2009, 60, 3311-3336.{{DOI|10.1093/jxb/erp204}}</ref> It acts at trace levels throughout the life of the plant by stimulating or regulating the [[ripening]] of [[fruit]], the opening of [[flower]]s, and the [[abscission]] (or shedding) of [[leaves]]. 
Commercial ripening rooms use "catalytic generators", to make ethylene gas, from a liquid supply of ethanol.  Typically, a gassing level of 500 ppm to 2,000 ppm is used, for 24 to 48 hours.  Care must be taken to control carbon dioxide levels in ripening rooms when gassing, as high temperature ripening (68F) has been seen to produce CO2 levels of 10% in 24 hours.<ref>[http://ne-postharvest.com/ripening.htm#controlledatmosphereripening External Link to More on Ethylene Gassing and Carbon Dioxide Control]</ref>
<!--To be do: How ethylene ripen the fruits.-->
===History of ethylene in plant biology===
Ethylene has been used in practice since the ancient Egyptians, who would gash figs in order to stimulate ripening (wounding stimulates ethylene production by plant tissues). The ancient Chinese would burn [[incense]] in closed rooms to enhance the ripening of pears. In 1864, it was discovered that gas leaks from street lights led to stunting of growth, twisting of plants, and abnormal thickening of stems.<ref name=Lin/> In 1901, a Russian scientist named Dimitry Neljubow showed that the active component was ethylene.<ref name="Neljobov_1901">{{cite journal | author = Neljubov D. | title = Uber die horizontale Nutation der Stengel von Pisum sativum und einiger anderen Pflanzen | journal = Beih Bot Zentralbl | volume = 10 | issue = | pages = 128–139 | year = 1901 | id = }}</ref> Doubt discovered that ethylene stimulated [[abscission]] in 1917.<ref name="Doubt_1917">{{cite journal | author = Doubt, Sarah L.| title = The Response of Plants to Illuminating Gas | journal = Botanical Gazette | url= http://www.jstor.org/pss/2469142 | volume = 63 | issue = 3| pages = 209–224 | year = 1917 | id = | doi = 10.1086/332006 }}</ref> It wasn't until 1934 that Gane reported that plants synthesize ethylene.<ref name="Gane_1934">{{cite journal | author = Gane R. | title = Production of ethylene by some fruits | journal = Nature| volume = 134| issue = | pages = 1008| year = 1934 id = | doi = 10.1038/1341008a0 }}</ref> In 1935, Crocker proposed that ethylene was the plant hormone responsible for fruit ripening as well as [[senescence]] of vegetative tissues.<ref>Crocker W, Hitchcock AE, Zimmerman PW. 1935 '''Similarities in the effects of ethlyene and the plant auxins.''' Contrib. Boyce Thompson Inst. 7. 231-48. Auxins Cytokinins IAA Growth substances, Ethylene</ref>

===Ethylene biosynthesis in plants===
[[Image:Yang-cycle.png|thumb|300px|Plant biosynthesis of ethylene]]Ethylene is produced from essentially all parts of higher plants, including leaves, stems, roots, flowers, fruits, tubers, and seedlings.
<blockquote> "Ethylene production is regulated by a variety of developmental and environmental factors. During the life of the plant, ethylene production is induced during certain stages of growth such as [[germination]], [[ripening]] of fruits, [[abscission]] of leaves, and [[senescence]] of flowers. Ethylene production can also be induced by a variety of external aspects such as mechanical wounding, environmental stresses, and certain chemicals including auxin and other regulators".<ref name=Yang_1984> {{cite journal | author = Yang, S. F., and Hoffman N. E. | title = Ethylene biosynthesis and its regulation in higher plants | journal = Ann. Rev. Plant Physiol. | volume = 35 | pages = 155–89 | year = 1984 | doi = 10.1146/annurev.pp.35.060184.001103}}</ref></blockquote> 

The [[biosynthesis]] of the hormone starts with conversion of the amino acid [[methionine]] to [[S-adenosyl methionine|S-adenosyl-L-methionine]] (SAM, also called Adomet) by the enzyme Met Adenosyltransferase. SAM is then converted to [[1-aminocyclopropane-1-carboxylic-acid]] (ACC) by the enzyme [[1-aminocyclopropane-1-carboxylate_synthase|ACC synthase (ACS)]]; the activity of ACS dertermines the rate of ethylene production, therefore regulation of this [[enzyme]] is key for the ethylene biosynthesis. The final step requires oxygen and involves the action of the enzyme [[Aminocyclopropanecarboxylate_oxidase|ACC-oxidase]] (ACO), formerly known as the Ethylene Forming Enzyme (EFE). Ethylene biosynthesis can be induced by endogenous or exogenous ethylene. ACC synthesis increases with high levels of [[auxin]]s, specially [[Indole]] [[acetic acid]] (IAA), and [[cytokinin]]s. ACC [[synthase]] is inhibited by [[abscisic acid]].

===Ethylene perception in plants===
Ethylene could be perceived by a transmembrane [[protein]] [[protein dimer|dimer]] complex. The [[gene]] [[encoding]] an ethylene receptor has been cloned in ''[[Arabidopsis thaliana]]'' and then in [[tomato]]. Ethylene receptors are encoded by multiple genes in the Arabidopsis and [[tomato]] [[genomes]]. The [[gene family]] comprises five receptors in Arabidopsis and at least six in tomato, most of which have been shown to bind ethylene. [[DNA]] sequences for ethylene receptors have also been identified in many other plant species and an ethylene binding protein has even been identified in [[Cyanobacteria]].<ref name=Lin/>

===Environmental and biological triggers of ethylene===
Environmental cues can induce the biosynthesis of the plant hormone. Flooding, drought, chilling, wounding, and pathogen attack can induce ethylene formation in the plant. In flooding, root suffers from lack of oxygen, or [[Hypoxia (environmental)|anoxia]], which leads to the synthesis of [[1-Aminocyclopropane-1-carboxylic acid]] (ACC). ACC is transported upwards in the plant and then oxidized in leaves. The product, the ethylene causes [[epinasty]] of the leaves.

One speculation recently put forth for epinasty <!--[http://www.planthormones.info/epinasty.htm]--> is the downward pointing leaves may act as pump handles in the wind. The ethylene may or may not additionally induce the growth of a valve in the [[xylem]], but the idea would be that the plant would harness the power of the wind to pump out more water from the roots of the plants than would normally happen with [[transpiration]].

===Physiological responses of plants===
Like the other plant hormones, ethylene is considered to have [[pleiotropic]] effects. This essentially means that it is thought that at least some of the effects of the hormone are unrelated. What is actually caused by the gas may depend on the tissue affected as well as environmental conditions. In the evolution of plants, ethylene would simply be a message that was coopted for unrelated uses by plants during different periods of the evolutionary development.

====List of plant responses to ethylene====
* Seedling triple response, thickening and shortening of [[hypocotyl]] with pronounced [[apical hook]]. This is thought to be a seedling's reaction to an obstacle in the soil such a stone, allowing it to push past the obstruction.
* In [[pollination]], when the pollen reaches the stigma, the precursor of the ethylene, [[1-Aminocyclopropane-1-carboxylic acid|ACC]], is secreted to the petal, the ACC releases ethylene with ACC oxidase.
* Stimulates leaf and flower [[senescence]]
* Stimulates senescence of mature [[xylem]] cells in preparation for plant use
* Inhibits shoot growth except in some habitually flooded plants like [[rice]]
* Induces leaf [[abscission]]
* Induces seed [[germination]]
* Induces [[root hair]] growth &ndash; increasing the efficiency of water and mineral absorption 
* Induces the growth of [[adventitious root]]s during flooding 
* Stimulates [[epinasty]] &ndash; leaf [[Petiole (botany)|petiole]] grows out, leaf hangs down and curls into itself 
* Stimulates [[fruit ripening]]
* Induces a [[climacteric (botany)|climacteric]] rise in {{dn|respiration}} in some fruit which causes a release of additional ethylene. This can be the one bad apple in a barrel spoiling the rest phenomenon.
* Affects neighboring individuals 
* Affects [[gravitropism]]
* Stimulates [[nutational]] bending
* Disease/wounding resistance 
* Inhibits stem growth outside of seedling stage
* Stimulates stem and cell broadening and lateral branch growth also outside of seedling stage
* Interference with [[auxin]] transport (with high [[auxin]] concentrations) 
* Inhibits [[stoma]]tal closing except in some water plants or habitually flooded ones such as some rice varieties, where the opposite occurs (conserving CO<sub>2</sub> and O<sub>2</sub>)
* Where ethylene induces stomatal closing, it also induces stem elongation 
* Induces flowering in [[pineapple]]s

====Commercial issues====
Ethylene shortens the shelf life of many fruits by hastening [[fruit ripening]] and [[floral senescence]]. [[Tomato]]es, [[banana]]s and [[apple]]s will ripen faster in the presence of ethylene. Bananas placed next to other fruits will produce enough ethylene to cause accelerated fruit ripening. Ethylene will shorten the shelf life of cut flowers and potted plants by accelerating floral senescence and floral [[abscission]]. Flowers and plants which are subjected to stress during shipping, handling, or storage produce ethylene causing a significant reduction in floral display. Flowers affected by ethylene include [[carnation]], [[Pelargonium|geranium]], [[petunia]], [[rose]], and many others.<ref>{{cite journal | title = Effect of ethylene on flower abscission: a survey |journal = Annals of Botany | volume = 89 | issue = 6 | pages = 689–693| year = 2002 | pmid = : 12102524 | doi = 10.1093/aob/mcf124 | author = Van Doorn, W. G.}}</ref>

Ethylene can cause significant economic losses for florists, markets, suppliers, and growers. Researchers have developed several ways to inhibit ethylene, including inhibiting ethylene synthesis and inhibiting ethylene perception. Aminoethoxyvinylglycine (AVG), Aminooxyacetic acid (AOA), and silver ions are ethylene inhibitors<ref name="dic_plant">{{cite book|last=Cassells |first=A. C. |coauthors=Peter B. Gahan|title=Dictionary of plant tissue culture|publisher=Haworth Press|date= 2006|pages=77|isbn=1560229195, 9781560229193|url=http://books.google.com/?id=cR5y5_vahAUC}}</ref><ref>{{cite book|last=Constabel|first=Friedrich |coauthors=Jerry P. Shyluk|title=Plant Cell and Tissue Culture|publisher=Springer|date=1994|pages=5|chapter=1: Initiation, Nutrition, and Maintenance of Plant Cell and Tissue Cultures |isbn=0792324935}}</ref>. Inhibiting ethylene synthesis is less effective for reducing post-harvest losses since ethylene from other sources can still have an effect. By inhibiting ethylene perception, fruits, plants and flowers don't respond to ethylene produced endogenously or from exogenous sources. Inhibitors of ethylene perception include compounds that have a similar shape to ethylene, but do not elicit the ethylene response. One example of an ethylene perception inhibitor is [[1-methylcyclopropene]] (1-MCP).

Commercial growers of [[bromeliads]], including [[pineapple]] plants, use ethylene to induce flowering. Plants can be induced to flower either by treatment with the gas in a chamber, or by placing a [[banana]] peel next to the plant in an enclosed area.

===Historical Significance===
Many geologists and scholars believe that the famous Greek Oracle at [[Delphi]] (the [[Pythia]]) went into her trance-like state as an effect of ethylene rising from ground faults.<ref name=Roach>{{cite news|title= Delphic Oracle's Lips May Have Been Loosened by Gas Vapors|author=John Roach|publisher=National Geographic|date=2001-08-14|url= http://news.nationalgeographic.com/news/2001/08/0814_delphioracle.html |accessdate=March 8, 2007 }}</ref>

==History==
Ethylene appears to have been discovered by [[Johann Joachim Becher]], who obtained it by heating [[ethanol]] with sulfuric acid;<ref>p. 611, [http://books.google.com/books?id=o7gtAAAAYAAJ ''A treatise on chemistry''], Henry Enfield Roscoe and Carl Schorlemmer, Appleton, 1878, vol. 1.</ref> he mentioned the gas in his ''Physica Subterranea'' (1669).<ref>p. 225, ''A History of Chemistry: From the Earliest Times Till the Present Day'', James Campbell Brown, reprint ed., Kessinger Publishing, 2006, ISBN 1428638318.</ref> [[Joseph Priestley]] also mentions the gas in his ''Experiments and observations relating to the various branches of natural philosophy: with a continuation of the observations on air'' (1779), where he reports that [[Jan Ingenhousz]] saw ethylene synthesized in the same way by a Mr. Enée in Amsterdam in 1777 and that Ingenhousz subsequently produced the gas himself.<ref>Appendix, §VIII, pp. 474 ff., [http://www.archive.org/stream/experimentsobser00prie#page/474/mode/2up ''Experiments and observations relating to the various branches of natural philosophy: with a continuation of the observations on air''], Joseph Priestley, London: printed for J. Johnson, 1779, vol. 1.</ref> The properties of ethylene were studied in 1795 by four [[Netherlands|Dutch]] chemists, Johann Rudolph Deimann, Adrien Paets van Troostwyck, Anthoni Lauwerenburgh and Nicolas Bondt, who found that it differed from [[hydrogen]] gas and that it contained both carbon and hydrogen.<ref>p. 612, Roscoe and Schorlemmer 1878.</ref> This group also discovered that ethylene could be combined with [[chlorine]] to produce the ''oil of the Dutch chemists'', [[1,2-Dichloroethane|1,2-dichloroethane]]; this discovery gave ethylene the name used for it at that time, ''olefiant gas'' (oil-making gas.)<ref>p. 613, Roscoe and Schorlemmer 1878; p. 157, [http://books.google.com/books?id=oKe808wkZzgC ''Handbook of organic chemistry: for the use of students''], William Gregory, ed. J. Milton Sanders, 4th American ed., New York: A. S. Barnes & Co., 1857.</ref>
 
In the mid-19th century, the suffix ''-ene'' (an Ancient Greek root added to the end of female names meaning "daughter of") was widely used to refer to a molecule or part thereof that contained one fewer hydrogen atoms than the molecule being modified. Thus, ''ethylene'' (C<sub>2</sub>H<sub>4</sub>) was the "daughter of [[ethyl group|ethyl]]" (C<sub>2</sub>H<sub>5</sub>). The name ethylene was used in this sense as early as 1852.

In 1866, the [[Germany|German]] chemist [[August Wilhelm von Hofmann]] proposed a system of hydrocarbon nomenclature in which the suffixes -ane, -ene, -ine, -one, and -une were used to denote the hydrocarbons with 0, 2, 4, 6, and 8 fewer hydrogens than their parent [[alkane]].<ref>{{cite web|url=http://www.chem.yale.edu/~chem125/125/history99/5Valence/Nomenclature/Hofmannaeiou.html|title=Hofmann's Proposal for Systematic Nomenclature of the Hydrocarbons|author=A. W. Hofmann, LL.D., F.R.S.|accessdate=2007-01-06|publisher=www.chem.yale.edu}}</ref> In this system, ethylene became ''ethene''. Hofmann's system eventually became the basis for the Geneva nomenclature approved by the International Congress of Chemists in 1892, which remains at the core of the [[IUPAC]] nomenclature. However, by that time, the name ethylene was deeply entrenched, and it remains in wide use today, especially in the chemical industry.

===Nomenclature===
The 1979 IUPAC nomenclature rules made an exception for retaining the non-systematic name ethylene<ref>[http://www.acdlabs.com/iupac/nomenclature/79/r79_53.htm#a_3__1 IUPAC nomenclature rule A-3.1 (1979)]</ref>, however, this decision was reversed in the 1993 rules<ref>[http://www.acdlabs.com/iupac/nomenclature/93/r93_684.htm Footnote to IUPAC nomenclature rule R-9.1, table 19(b)]</ref> so the IUPAC name is now ''ethene''.

===Safety===
Like all hydrocarbons, ethylene is an [[asphyxiant]] and combustable. It has been used as an anesthetic.<ref>Heinz Zimmermann and Roland Walz "Ethylene" in Ullmann's Encyclopedia of Industrial Chemistry 2009, Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a10_045.pub3}}</ref>

==See also==
{{Commons category|Ethylene}}
{{Alkenes}}
{{Functional Groups}}
{{BranchesofChemistry}}
{{Plant_hormones}}
{{General anesthetics}}

==References==
{{reflist|2}}

===Appendix: ethylene production facilities===
[[Alberta]], [[Canada]]
* [[Joffre]], [[Joffre, Alberta|Joffre]], ([[Dow Chemical]] and [[Nova Chemicals]]), 2165 kta ethylene
[[Ontario]], [[Canada]]
* Sarnia, [[Sarnia, Ontario|Sarnia]], ([[Nova Chemicals]]), 
[[Louisiana]], [[United States]]
* [[Hahnville]], [[Hahnville, Louisiana|Hahnville]], ([[Dow Chemical]]), 
* Lake Charles, [[Lake Charles, Louisiana|Lake Charles]], ([[Westlake Chemical]]), 
* Norco, [[Norco, Louisiana|Norco]], ([[Shell Chemical]]), 1500 kta ethylene
[[Texas]], [[United States]]
* Alvin, [[Alvin, Texas|Alvin]], ([[Ineos]]), 
* Corpus Christi, [[Corpus Christi, Texas|Corpus Christi]], ([[LyondellBasell]]), 
* Deer Park, [[Deer Park, Texas|Deer Park]], ([[Shell Chemical]]), 1200 kta ethylene
* Orange, [[Orange, Texas|Orange]], ([[DuPont]]),
* Port Arthur, [[Port Arthur, Texas|Port Arthur]], ([[BASF and Total Petrochemical]]), 
Nanhai, [[China]]
* Nanhai, [[Nanhai, China|Nanhai]], ([[Shell Chemical]]), not available kta ethylene
[[Ras Laffan Industrial City]], [[Qatar]]
* [[Ras Laffan Industrial City]], [[Ras Laffan Industrial City, Qatar|Ras Laffan Industrial City]], ([[QAPCO]]), 1300 kta ethylene
[[Texas]], [[United States]]
*[[Channelview]], [[Texas|Channelview]], ([[LyondellBasell]]), 1450 kta ethylene
*[[National Iranian Petrochemical Company]], 1320 kta ethylene
*[[ Baytown]], [[(Chevron Chemicals Company)]], [[ Cedar Bayou Plant]], not available kta ethylene

==Further reading==
Ethylene hormone receptor action in Arabidopsis. Chang C, Stadler R. Bioessays. 2001 Jul;23(7):619-27. Review. PMID: 11462215

Differential petiole growth in Arabidopsis thaliana: photocontrol and hormonal regulation. Millenaar FF, van Zanten M, Cox MC, Pierik R, Voesenek LA, Peeters AJ. New Phytol. 2009 Jun 24. [Epub ahead of print] PMID: 19558423

==External links==
*[http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc04/icsc0475.htm International Chemical Safety Card 0475]
*[http://ecb.jrc.it/ European Chemicals Bureau]
*[http://www.planthormones.info Speculations Towards a General Plant Hormone Theory]
*[http://www.novachem.com/productservices/docs/Ethylene_MSDS_EN.pdf MSDS]

[[Category:Alkenes]]
[[Category:Plant hormones]]
[[Category:Monomers]]
[[Category:General anesthetics]]

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