View source for Chemistry:Ethylene oxide

{{Short description|Cyclic compound (C2H4O)}}
{{chembox
|Watchedfields  = changed
|verifiedrevid  = 446701253
|ImageFileL1 = Ethylene oxide.svg
|ImageSizeL1 = 100 px
|ImageFileR1 = Ethylene-oxide-from-xtal-3D-balls.png
|ImageSizeR1 = 150 px
|PIN = Oxirane<ref>{{cite book |author=[[Organization:International Union of Pure and Applied Chemistry|International Union of Pure and Applied Chemistry]] |date=2014 |title=Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 |publisher=[[Organization:Royal Society of Chemistry|The Royal Society of Chemistry]] |pages=714 |doi=10.1039/9781849733069 |isbn=978-0-85404-182-4}}</ref>
|SystematicName = Epoxyethane<br />Oxacyclopropane
|OtherNames = Ethylene oxide<br />Dimethylene oxide<br />1,2-Epoxyethane<br />[3]-crown-1<br />Epoxide
|Section1 = {{Chembox Identifiers
|Abbreviations = EO, EtO
|Beilstein = 102378
|ChEMBL = 1743219
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|ChemSpiderID = 6114
|Gmelin = 676
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = JJH7GNN18P
|UNNumber = 1040
|InChIKey = IAYPIBMASNFSPL-UHFFFAOYAX
|StdInChI_Ref = {{stdinchicite|correct|chemspider}}
|StdInChI = 1S/C2H4O/c1-2-3-1/h1-2H2
|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
|StdInChIKey = IAYPIBMASNFSPL-UHFFFAOYSA-N
|CASNo = 75-21-8
|CASNo_Ref = {{cascite|correct|CAS}}
|EINECS = 200-849-9
|PubChem = 6354
|SMILES = O1CC1
|InChI = 1/C2H4O/c1-2-3-1/h1-2H2
|RTECS = KX2450000
|MeSHName = Ethylene+Oxide
|ChEBI_Ref = {{ebicite|correct|EBI}}
|ChEBI = 27561
|KEGG_Ref = {{keggcite|correct|kegg}}
|KEGG = D03474
}}
|Section2 = {{Chembox Properties
|Formula = {{chem2|C2H4O}}
|MolarMass = 44.052{{nbsp}}g·mol<sup>−1</sup><ref name=r3430>Haynes, p. 3.430</ref>
|Appearance = Colorless gas
|Odor = Like diethyl ether<ref>Ethylene oxide, odor</ref>
|Density = 0.8821{{nbsp}}g·cm<sup>−3</sup><ref name=r3430/>
|Dipole = 1.94{{nbsp}}D<ref name=r1520/>
|MeltingPtC = −112.46
|MeltingPt_ref =<ref name=r3430/>
|BoilingPtC = 10.4
|BoilingPt_ref =<ref name=r3430/>
|Solubility = Miscible
|VaporPressure = 1.46{{nbsp}}atm (20{{nbsp}}°C)<ref name=PGCH/>
|RefractIndex = 1.3597 (589{{nbsp}}nm)<ref name=r3430/>
|MagSus = −30.5·10<sup>−6</sup>{{nbsp}}cm<sup>3</sup>/mol<ref>Haynes, p. 3.576</ref>
}}
|Section3 = {{Chembox Thermochemistry
|DeltaHf = −52.6{{nbsp}}kJ·mol<sup>−1</sup><ref name=r522>Haynes, p. 5.22</ref>
|DeltaGf = −13.0{{nbsp}}kJ·mol{{sup|−1}}<ref name=r522/>
|Entropy = 242.5{{nbsp}}J·mol<sup>−1</sup>·K<sup>−1</sup><ref name=r522/>
|HeatCapacity = 47.9{{nbsp}}J·mol<sup>−1</sup>·K<sup>−1</sup><ref name=r522/>
}}
|Section4 = {{Chembox Hazards
|ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics0155.htm ICSC 0155]
|GHSPictograms = {{GHS02}}{{GHS04}}{{GHS06}}{{GHS08}}
|MainHazards = [[Biology:Carcinogen|Carcinogen]]<br />Extremely flammable
|NFPA-H = 3
|NFPA-F = 4
|NFPA-R = 2
|HPhrases = {{H-phrases|220|230|280|301|314|331|335|336|340|350|360FD|372}}
|PPhrases = {{P-phrases|202|210|260|280|301+310+330|303+361+353|305+351+338+310|410+403}}<ref name="sigmaaldrich 2020">{{cite web |title=Ethylene oxide 387614 |url=https://www.sigmaaldrich.com/catalog/product/aldrich/387614?lang=en&region=GB |website=Sigma-Aldrich |access-date=1 September 2020 |archive-url=https://web.archive.org/web/20201205212012/https://www.sigmaaldrich.com/catalog/product/aldrich/387614?lang=en&region=US |archive-date=5 December 2020 |url-status=live}} [https://archive.org/download/ethylene-oxide-msds/Ethylene%20oxide%20MSDS.pdf Alt URL]</ref>
|FlashPtC = −20
|FlashPt_ref =<ref name=r1520>Haynes, p. 15.20</ref>
|AutoignitionPtC = 429
|AutoignitionPt_ref=<ref name=r1520/>
|ExploLimits = 3 to 100%
|PEL = TWA 1{{nbsp}}ppm 5{{nbsp}}ppm [15-minute excursion]<ref name=PGCH>{{PGCH|0275}}</ref>
|REL = Ca TWA <0.1{{nbsp}}ppm (0.18{{nbsp}}mg/m<sup>3</sup>) C 5{{nbsp}}ppm (9{{nbsp}}mg/m<sup>3</sup>) [10-min/day]<ref name=PGCH/>
|IDLH = Ca [800{{nbsp}}ppm]<ref name=PGCH/>
|LC50 = 836{{nbsp}}ppm (mouse, 4{{nbsp}}hr) <br />4000{{nbsp}}ppm (rat, 4{{nbsp}}hr) <br />800{{nbsp}}ppm (rat, 4{{nbsp}}hr)<br />819{{nbsp}}ppm (guinea pig, 4{{nbsp}}hr)<br />1460{{nbsp}}ppm (rat, 4{{nbsp}}hr)<br />835{{nbsp}}ppm (mouse, 4{{nbsp}}hr)<br />960{{nbsp}}ppm (dog, 4{{nbsp}}hr)<ref>{{IDLH|75218|Ethylene oxide}}</ref>
}}
|Section5 = {{Chembox Related
|OtherFunction = [[Chemistry:Aziridine|Aziridine]],<br /> [[Chemistry:Thiirane|Thiirane]],<br /> [[Chemistry:Borirane|Borirane]]
|OtherFunction_label = heterocycles
}}
}}

'''Ethylene oxide''' is an [[Chemistry:Organic compound|organic compound]] with the [[Chemistry:Chemical formula|formula]] {{chem2|C2H4O}}. It is a cyclic [[Chemistry:Ether|ether]] and the simplest [[Chemistry:Epoxide|epoxide]]: a three-membered [[Chemistry:Ring|ring]] consisting of one [[Chemistry:Oxygen|oxygen]] atom and two [[Chemistry:Carbon|carbon]] atoms. Ethylene oxide is a colorless and flammable gas with a faintly sweet odor.  Because it is a strained ring, ethylene oxide easily participates in a number of [[Chemistry:Addition reaction|addition reaction]]s that result in ring-opening. Ethylene oxide is [[Chemistry:Isomer|isomer]]ic with [[Chemistry:Acetaldehyde|acetaldehyde]] and with [[Chemistry:Vinyl alcohol|vinyl alcohol]]. Ethylene oxide is industrially produced by oxidation of [[Chemistry:Ethylene|ethylene]] in the presence of a [[Chemistry:Silver|silver]] [[Chemistry:Catalyst|catalyst]].

The reactivity that is responsible for many of ethylene oxide's hazards also makes it useful. Although too dangerous for direct household use and generally unfamiliar to consumers, ethylene oxide is used for making many consumer products as well as non-consumer chemicals and intermediates. These products include detergents, thickeners, solvents, plastics, and various organic chemicals such as [[Chemistry:Ethylene glycol|ethylene glycol]], ethanolamines, simple and complex glycols, polyglycol ethers, and other compounds. Although it is a vital raw material with diverse applications, including the manufacture of products like [[Chemistry:Polysorbate 20|polysorbate 20]] and [[Chemistry:Polyethylene glycol|polyethylene glycol]] (PEG) that are often more effective and less toxic than alternative materials, ethylene oxide itself is a very hazardous substance. At room temperature it is a very flammable, carcinogenic, mutagenic, irritating, and anaesthetic gas.<ref name=Ullmann/>

Ethylene oxide is a surface [[Chemistry:Disinfectant|disinfectant]] that is widely used in hospitals and the medical equipment industry to [[Biology:Sterilization (microbiology)#Ethylene oxide|replace steam in the sterilization]] of heat-sensitive tools and equipment, such as disposable plastic syringes.<ref>{{cite book|url=https://books.google.com/books?id=oJy5wdzi0yUC&pg=PA309|page=309|title=Encyclopedia of Chemical Processing and Design|volume=20|author1=McKetta, John J.  |author2=Cunningham, William A. |publisher=CRC Press|year=1984|isbn=0-8247-2470-4}}</ref> It is so flammable and extremely explosive that it is used as a main component of thermobaric weapons;<ref name=e1/><ref name=e2/> therefore, it is commonly handled and shipped as a refrigerated liquid to control its hazardous nature.<ref name=Ullmann>Rebsdat, Siegfried and Mayer, Dieter (2005) "Ethylene Oxide" in ''Ullmann's Encyclopedia of Industrial Chemistry''. Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a10_117}}.</ref><ref>[https://www.superfoodly.com/ethylene-oxide-sterilization-non-eto-spices/ ''Ethylene Oxide Sterilization: Are ETO Treated Spices Safe?''], SuperFoodly, 10 April 2017</ref>

==History==
Ethylene oxide was first reported in 1859 by the {{wipe|France}} chemist Charles-Adolphe Wurtz,<ref>{{cite journal|author=Wurtz, A.|journal= Comptes rendus|volume= 48|pages= 101–105 |year=1859| title= Sur l'oxyde d'éthylène| url= http://gallica.bnf.fr/ark:/12148/bpt6k30054/f101.image}}</ref> who prepared it by treating 2-chloroethanol with [[Chemistry:Potassium hydroxide|potassium hydroxide]]:

:<chem>Cl-CH2CH2-OH + KOH -> (CH2CH2)O + KCl + H2O</chem>

Wurtz measured the [[Physics:Boiling point|boiling point]] of ethylene oxide as {{Convert|13.5|C|}}, slightly higher than the present value, and discovered the ability of ethylene oxide to react with acids and salts of metals.<ref name="oe1">{{cite book
| chapter = Part I. Structure and properties of ethylene oxide. Features of the reactivity of ethylene oxide and the structure of its molecules
| title = Ethylene oxide
|editor1=Zimakov, P.V. |editor2=Dyment, O. H. | publisher = Khimiya
| year = 1967
| pages = 15–17}}</ref> Wurtz mistakenly assumed that ethylene oxide has the properties of an organic base. This misconception persisted until 1896 when Georg Bredig found that ethylene oxide is not an [[Physics:Electrolyte|electrolyte]].<ref name="oe1" /><ref>{{cite journal|author=Bredig, G.|author2= Usoff, A. |year=1896|url=https://books.google.com/books?id=0cPmAAAAMAAJ&pg=PA116 |title=Ist Acetylen ein Elektrolyt?|trans-title=Is acetylene an electrolyte?|journal=Zeitschrift für Elektrochemie|volume=3|pages=116–117}}</ref> That it differed from other [[Chemistry:Ether|ether]]s — particularly by its propensity to engage in the addition reactions typical of [[Chemistry:Saturated and unsaturated compounds|unsaturated compounds]] — had long been a matter of debate. The heterocyclic triangular structure of ethylene oxide was proposed by 1868 or earlier.<ref>Eugen F. von Gorup-Besanez, ed., ''Lehrbuch der organischen Chemie für den Unterricht auf Universitäten'' … [Textbook of Organic Chemistry for Instruction at Universities … ], 3rd ed. (Braunschweig, Germany: Friedrich Vieweg und Sohn, 1868), vol. 2, [https://archive.org/details/bub_gb_UJyCAAAAIAAJ/page/n314 p. 286].<br /> See also [https://books.google.com/books?id=oc5Qth0MKE8C&pg=PA253 p. 253] of the 1876 edition: Eugen F. von Gorup-Besanez, ed., ''Lehrbuch der organischen Chemie für den Unterricht auf Universitäten'' …, 5th ed. (Braunschweig, Germany: Friedrich Vieweg und Sohn, 1876), vol. 2.</ref>

Wurtz's 1859 synthesis long remained the only method of preparing ethylene oxide, despite numerous attempts, including by Wurtz himself, to produce ethylene oxide directly from [[Chemistry:Ethylene|ethylene]].<ref name="ect">{{cite book| chapter = Ethylene Oxide| title = Kirk-Othmer Encyclopedia of Chemical Technology. Elastomers, synthetic to Expert Systems| edition = 4| location = New York| publisher = John Wiley & Sons| year = 1994| isbn=978-0-471-48514-8| volume = 9| pages = 450–466}}</ref> Only in 1931 did French chemist Theodore Lefort develop a method of direct oxidation of ethylene in the presence of [[Chemistry:Silver|silver]] [[Chemistry:Catalyst|catalyst]].<ref>Lefort, T.E. (23 April 1935) "Process for the production of ethylene oxide". {{US Patent|1998878}}</ref> Since 1940, almost all industrial production of ethylene oxide has relied on this process.<ref>{{cite journal|title= Manufacture and Uses of Ethylene Oxide and Ethylene Glycol| author= McClellan, P. P. | journal= Ind. Eng. Chem.|year= 1950| volume= 42|pages= 2402–2407| doi= 10.1021/ie50492a013|issue= 12}}</ref> Sterilization by ethylene oxide for the preservation of spices was patented in 1938 by the {{wipe|United States}} chemist Lloyd Hall. Ethylene oxide achieved industrial importance during [[Social:World War I|World War I]] as a precursor to both the coolant [[Chemistry:Ethylene glycol|ethylene glycol]] and the [[Chemistry:Chemical weapon|chemical weapon]] [[Chemistry:Sulfur mustard|mustard gas]].{{fact|date=October 2023}}

==Molecular structure and properties==
[[File:Ethylene-oxide.png|250px|thumb|right]]
[[File:Ethylene oxide refrigerated liquid.jpg|thumb|right|Condensed ethylene oxide]]

The epoxy cycle of ethylene oxide is an almost regular triangle with bond angles of about 60° and a significant angular [[Chemistry:Strain|strain]] corresponding to the energy of 105 kJ/mol.<ref>{{cite encyclopedia| chapter= Voltage molecules| title = Chemical Encyclopedia| editor = Knunyants, I. L.| encyclopedia = Soviet encyclopedia| year = 1988| volume = 3| pages = 330–334}}</ref><ref name="traven">{{cite book|author = Traven VF| title = Organic chemistry: textbook for schools| editor = V. F. Traven| publisher = ECC "Academkniga"| year = 2004| volume = 2| pages = 102–106| isbn = 5-94628-172-0}}</ref> For comparison, in [[Chemistry:Alcohol|alcohol]]s the C–O–H angle is about 110°; in [[Chemistry:Ether|ether]]s, the C–O–C angle is 120°. The [[Physics:Moment of inertia|moment of inertia]] about each of the principal axes are ''I<sub>A</sub>'' = {{val|32.921|e=-40|u=g·cm{{sup|2}}}}, ''I<sub>B</sub>'' = {{val|37.926|e=-40|u=g·cm{{sup|2}}}} and ''I<sub>C</sub>'' = {{val|59.510|e=-40|u=g·cm{{sup|2}}}}.<ref>{{cite journal| author = Cunningham G. L.|author2= Levan W. I.|author3= Gwinn W. D.| title = The Rotational Spectrum of Ethylene Oxide| doi=10.1103/PhysRev.74.1537| journal = Phys. Rev.| year = 1948| volume = 74| page = 1537| issue = 10| bibcode= 1948PhRv...74.1537C}}</ref>

The relative instability of the carbon-oxygen bonds in the molecule is revealed by the comparison in the table of the energy required to break two C–O bonds in the ethylene oxide or one C–O bond in [[Chemistry:Ethanol|ethanol]] and [[Chemistry:Dimethyl ether|dimethyl ether]]:<ref>{{cite book| title = Energy of chemical bonds. Ionization potentials and electron affinity| editor =Kondrat'ev, VN| publisher = Nauka| year = 1974| pages = 77–78}}</ref>
{| Class = "wikitable" style="text-align:center"
 ! Reaction
 ! ΔH°<sub>298</sub>, kJ/mol
 ! Method
|-
| '''{{chem2|(C2H4)O -> C2H4 + O}}''' (cleavage of two bonds)
| 354.38
| Calculated, from atomic enthalpies
|-
|'''{{chem2|[[Chemistry:Ethanol|C2H5OH]] -> C2H5 + OH}}''' (breaking one bond)
| 405.85
| Electron impact
|-
|'''{{chem2|[[Chemistry:Dimethyl ether|CH3OCH3]] -> CH3O + CH3}}''' (breaking one bond)
| 334.72
| Calculated using enthalpies of radicals formation
 |}

This instability correlates with its high reactivity, explaining the ease of its [[Physics:Cyclic compound|ring-opening]] reactions (see Chemical properties).

==Physical properties==
Ethylene oxide is a colorless gas at {{Convert|25|C|}} and is a mobile liquid at {{Convert|0|C|}} – viscosity of liquid ethylene oxide at 0&nbsp;°C is about 5.5 times lower than that of water. The gas has a characteristic sweet odor of ether, noticeable when its concentration in air exceeds 500{{nbsp}}ppm.<ref name="atsdr">{{cite web
| url = http://www.atsdr.cdc.gov/MHMI/mmg137.html
| title = Medical Management Guidelines for Ethylene Oxide
| work = Medical Management Guidelines (MMGs)
| publisher = Agency for Toxic Substances and Disease Registry
| access-date = 29 September 2009
| archive-url = https://www.webcitation.org/615rykXUP?url=http://www.atsdr.cdc.gov/MHMI/mmg137.html
| archive-date = 21 August 2011
| url-status = dead
}}</ref> Ethylene oxide is readily soluble in water, [[Chemistry:Ethanol|ethanol]], [[Chemistry:Diethyl ether|diethyl ether]] and many organic solvents.<ref>{{cite web
| url = http://dic.academic.ru/dic.nsf/bse/154711/Этилена
| title = Этилена окись (Ethylene oxide)
| publisher = [[Great Soviet Encyclopedia]]
| access-date = 25 September 2009
| language =ru
}}</ref>

Main thermodynamical constants are:<ref name="sch1">{{cite web | date = 1 April 2009| url= http://chemanalytica.com/book/novyy_spravochnik_khimika_i_tekhnologa/12_obshchie_svedeniya/6084 | title = Термодинамические показатели органических соединений | publisher = ChemAnalitica.com | access-date = 21 September 2009}}</ref>
* The [[Physics:Surface tension|surface tension]] of liquid ethylene oxide, at the interface with its own vapor, is {{Convert|35.8|mJ/m2||abbr=on}} at {{Convert|-50.1|C|}} and {{Convert|27.6|mJ/m2||abbr=on}} at {{Convert|-0.1|C|}}.<ref>{{cite web| date = 1 April 2009| url = http://chemanalytica.com/book/novyy_spravochnik_khimika_i_tekhnologa/12_obshchie_svedeniya/6118| title = Surface tension of liquefied gas at the border with its own steam| publisher = ChemAnalitica.com| access-date = 21 September 2009}}</ref>
* The boiling point increases with the vapor pressure as follows:<ref>{{cite web| date = 1 April 2009| url = http://chemanalytica.com/book/novyy_spravochnik_khimika_i_tekhnologa/12_obshchie_svedeniya/6061| title = Boiling point or sublimation (°C) organic matter in the vapor pressure above 101.3 kPa| publisher =ChemAnalitica.com| access-date = 21 September 2009}}</ref> {{Convert|57.7|C|}} ({{Convert|2|atm|kPa psi|abbr=on}}), {{Convert|83.6|C|}} ({{Convert|5|atm|kPa psi|abbr=on}}), and {{Convert|114.0|C|}} ({{Convert|10|atm|kPa psi|abbr=on}}).
* [[Physics:Viscosity|Viscosity]] decreases with temperature with the values of 0.577{{nbsp}}kPa·s at {{Convert|-49.8|C|}}, 0.488 kPa·s at {{Convert|-38.2|C|}}, 0.394{{nbsp}}kPa·s at {{Convert|-21.0|C|}}, and 0.320{{nbsp}}kPa·s at {{Convert|0|C|}}.<ref>{{cite web| date = 1 April 2009| url=http://chemanalytica.com/book/novyy_spravochnik_khimika_i_tekhnologa/12_obshchie_svedeniya/6112| title = Viscosity of organic compounds| publisher = ChemAnalitica.com| access-date = 21 September 2009}}</ref>

Between {{Convert|−91|and|10.5|C}}, vapor pressure ''p'' (in mmHg) varies with temperature (''T'' in °C) as 
:<math>\lg p = 6.251 - \frac{1115.1}{244.14 + T}</math>.<ref>{{cite web| date = 1 April 2009| url = http://chemanalytica.com/book/novyy_spravochnik_khimika_i_tekhnologa/12_obshchie_svedeniya/6063| title = Vapor pressure of organic compounds| publisher = ChemAnalitica.com| access-date = 21 September 2009}}</ref>

{| Class = "wikitable" style="text-align:center"
|+ Properties of liquid ethylene oxide<ref name="ect" />
|-
! Temperature, °C
! Vapor pressure, kPa
! Enthalpy of the liquid, J/g
! Enthalpy of vaporization, J/g
! Density, kg/L
! [[Physics:Heat capacity|Heat capacity]], J/(kg·K)
! [[Physics:Thermal conductivity|Thermal conductivity]], W/(m·K)
|-
| −40
| 8.35
| 0
| 628.6
| 0.9488
| 1878
| 0.20
|-
| −20
| 25.73
| 38.8
| 605.4
| 0.9232
| 1912
| 0.18
|-
| 0
| 65.82
| 77.3
| 581.7
| 0.8969
| 1954
| 0.16
|-
| 20
| 145.8
| 115.3
| 557.3
| 0.8697
| 2008
| 0.15
|-
| 40
| 288.4
| 153.2
| 532.1
| 0.8413
| 2092
| 0.14
|-
| 60
| 521.2
| 191.8
| 505.7
| 0.8108
| 2247
| 0.14
|-
| 80
| 875.4
| 232.6
| 477.4
| 0.7794
| 2426
| 0.14
|-
| 100
| 1385.4
| 277.8
| 445.5
| 0.7443
| 2782
| 0.13
|-
| 120
| 2088
| 330.4
| 407.5
| 0.7052
| 3293
| N/A*
|-
| 140
| 3020
| 393.5
| 359.4
| 0.6609
| 4225
| N/A
|-
| 160
| 4224
| 469.2
| 297.1
| 0.608
| N/A
| N/A
|-
| 180
| 5741
| 551.2
| 222.5
| 0.533
| N/A
| N/A
|-
| 195.8
| 7191
| N/A
| N/A
| N/A
| N/A
| N/A
|}
<nowiki>*</nowiki>N/A – data not available.

{| Class = "wikitable" style="text-align:center"
|+ Properties of ethylene oxide vapor <ref name="ect" />
|-
! Temperature, K
! Entropy, J/(mol·K)
! Heat of formation, kJ/mol
! Free energy of formation, kJ/mol
! Viscosity, μPa·s
! Thermal conductivity, W/(m·K)
! Heat capacity, J/(mol·K)
|-
| 298
| 242.4
| −52.63
| −13.10
| N/A
| N/A
| 48.28
|-
| 300
| 242.8
| −52.72
| −12.84
| 9.0
| 0.012
| 48.53
|-
| 400
| 258.7
| −56.53
| 1.05
| 13.5
| 0.025
| 61.71
|-
| 500
| 274.0
| −59.62
| 15.82
| 15.4
| 0.038
| 75.44
|-
| 600
| 288.8
| −62.13
| 31.13
| 18.2
| 0.056
| 86.27
|-
| 700
| 302.8
| −64.10
| 46.86
| 20.9
| 0.075
| 95.31
|-
| 800
| 316.0
| −65.61
| 62.80
| N/A
| 0.090
| 102.9
|}
<nowiki>*</nowiki>N/A – data not available.

==Chemical properties==
Ethylene oxide readily reacts with diverse compounds with opening of the ring. Its typical reactions are with nucleophiles which proceed via the '''[[Chemistry:Nucleophilic substitution|S<sub>N</sub>2]]''' mechanism both in acidic (weak nucleophiles: water, alcohols) and alkaline media (strong nucleophiles: OH<sup>−</sup>, RO<sup>−</sup>, NH<sub>3</sub>, RNH<sub>2</sub>, RR'NH, etc.).<ref name="traven" /> The general reaction scheme is

: [[File:Ethylene oxide reactions.png|400px|Ethylene oxide reactions]]

and more specific reactions are described below.

===Addition of water and alcohols===
Aqueous solutions of ethylene oxide are rather stable and can exist for a long time without any noticeable chemical reaction, but adding a small amount of acid, such as strongly diluted [[Chemistry:Sulfuric acid|sulfuric acid]], immediately leads to the formation of [[Chemistry:Ethylene glycol|ethylene glycol]], even at room temperature:

: (CH<sub>2</sub>CH<sub>2</sub>)O + H<sub>2</sub>O → HO–CH<sub>2</sub>CH<sub>2</sub>–OH

The reaction also occurs in the gas phase, in the presence of a [[Chemistry:Phosphoric acid|phosphoric acid]] salt as a catalyst.<ref name="oe3">{{cite book| chapter= Chapter III. Review of the individual reactions of ethylene oxide| title = Ethylene oxide|editor1=Zimakov, P.V. |editor2=Dyment, O. H.| publisher = Khimiya| year = 1967| pages = 90–120}}</ref>

The reaction is usually carried out at about {{Convert|60|C|}} with a large excess of water, in order to prevent the reaction of the formed ethylene glycol with ethylene oxide that would form [[Chemistry:Diethylene glycol|di-]] and [[Chemistry:Triethylene glycol|triethylene glycol]]:<ref>{{cite web| url = http://www.chemguide.co.uk/organicprops/alkenes/epoxyethane.html| title = Epoxyethane (Ethylene Oxide)| work = Alkenes menu| publisher = Chemguide| access-date = 5 October 2009}}</ref>

:2 (CH<sub>2</sub>CH<sub>2</sub>)O + H<sub>2</sub>O → HO–CH<sub>2</sub>CH<sub>2</sub>–O–CH<sub>2</sub>CH<sub>2</sub>–OH

:3 (CH<sub>2</sub>CH<sub>2</sub>)O + H<sub>2</sub>O → HO–CH<sub>2</sub>CH<sub>2</sub>–O–CH<sub>2</sub>CH<sub>2</sub>–O–CH<sub>2</sub>CH<sub>2</sub>–OH

The use of alkaline catalysts may lead to the formation of [[Chemistry:Polyethylene glycol|polyethylene glycol]]:

:n (CH<sub>2</sub>CH<sub>2</sub>)O + H<sub>2</sub>O → HO–(–CH<sub>2</sub>CH<sub>2</sub>–O–)<sub>n</sub>–H

Reactions with [[Chemistry:Alcohol|alcohol]]s proceed similarly yielding ethylene glycol ethers:

: (CH<sub>2</sub>CH<sub>2</sub>)O + C<sub>2</sub>H<sub>5</sub>OH → HO–CH<sub>2</sub>CH<sub>2</sub>–OC<sub>2</sub>H<sub>5</sub>

:2 (CH<sub>2</sub>CH<sub>2</sub>)O + C<sub>2</sub>H<sub>5</sub>OH → HO–CH<sub>2</sub>CH<sub>2</sub>–O–CH<sub>2</sub>CH<sub>2</sub>–OC<sub>2</sub>H<sub>5</sub>

Reactions with lower alcohols occur less actively than with water and require more severe conditions, such as heating to {{Convert|160|C|}} and pressurizing to {{Convert|3|MPa||abbr=on}} and adding an acid or alkali catalyst.

Reactions of ethylene oxide with fatty alcohols proceed in the presence of [[Chemistry:Sodium|sodium]] metal, [[Chemistry:Sodium hydroxide|sodium hydroxide]] or [[Chemistry:Boron trifluoride|boron trifluoride]] and are used for the synthesis of surfactants.<ref name="oe3" />

===Addition of carboxylic acids and their derivatives===
Reactions of ethylene oxide with [[Chemistry:Carboxylic acid|carboxylic acid]]s in the presence of a catalyst results in glycol mono- and diesters:

: (CH<sub>2</sub>CH<sub>2</sub>)O + CH<sub>3</sub>CO<sub>2</sub>H → HOCH<sub>2</sub>CH<sub>2</sub>–O<sub>2</sub>CCH<sub>3</sub>

: (CH<sub>2</sub>CH<sub>2</sub>)O + (CH<sub>3</sub>CO)<sub>2</sub>O → CH<sub>3</sub>CO<sub>2</sub>CH<sub>2</sub>CH<sub>2</sub>O<sub>2</sub>CCH<sub>3</sub>

The addition of acid [[Chemistry:Amide|amide]]s proceeds similarly:
: (CH<sub>2</sub>CH<sub>2</sub>)O + CH<sub>3</sub>CONH<sub>2</sub> → HOCH<sub>2</sub>CH<sub>2</sub>NHC(O)CH<sub>3</sub>

Addition of ethylene oxide to higher carboxylic acids is carried out at elevated temperatures (typically {{Convert|140-180|C|}}) and pressure ({{Convert|0.3-0.5|MPa||abbr=on}}) in an inert atmosphere, in presence of an alkaline catalyst (concentration 0.01–2%), such as hydroxide or carbonate of sodium or potassium.<ref>{{cite book| title = Nonionic surfactants: organic chemistry|editor1=van Os |editor2=N. M.| publisher = CRC Press| year = 1998| pages = 129–131|url=https://books.google.com/books?id=YoZ6CjYNLoQC&pg=PA129| isbn = 978-0-8247-9997-7}}</ref> The carboxylate ion acts as [[Chemistry:Nucleophile|nucleophile]] in the reaction:

: (CH<sub>2</sub>CH<sub>2</sub>)O + RCO<sub>2</sub><sup>−</sup> → RCO<sub>2</sub>CH<sub>2</sub>CH<sub>2</sub>O<sup>−</sup>

:RCO<sub>2</sub>CH<sub>2</sub>CH<sub>2</sub>O<sup>−</sup> + RCO<sub>2</sub>H → RCO<sub>2</sub>CH<sub>2</sub>CH<sub>2</sub>OH + RCO<sub>2</sub><sup>−</sup>

===Adding ammonia and amines===
Ethylene oxide reacts with [[Chemistry:Ammonia|ammonia]] forming a mixture of mono-, di- and tri- [[Chemistry:Ethanolamine|ethanolamine]]s. The reaction is stimulated by adding a small amount of water.

: (CH<sub>2</sub>CH<sub>2</sub>)O + NH<sub>3</sub> → HO–CH<sub>2</sub>CH<sub>2</sub>–NH<sub>2</sub>

:2 (CH<sub>2</sub>CH<sub>2</sub>)O + NH<sub>3</sub> → (HO–CH<sub>2</sub>CH<sub>2</sub>)<sub>2</sub>NH

:3 (CH<sub>2</sub>CH<sub>2</sub>)O + NH<sub>3</sub> → (HO–CH<sub>2</sub>CH<sub>2</sub>)<sub>3</sub>N

Similarly proceed the reactions with primary and secondary amines:

: (CH<sub>2</sub>CH<sub>2</sub>)O + RNH<sub>2</sub> → HO–CH<sub>2</sub>CH<sub>2</sub>–NHR

Dialkylamino ethanols can further react with ethylene oxide, forming amino polyethylene glycols:<ref name="ect" />

:n (CH<sub>2</sub>CH<sub>2</sub>)O + R<sub>2</sub>NCH<sub>2</sub>CH<sub>2</sub>OH → R<sub>2</sub>NCH<sub>2</sub>CH<sub>2</sub>O–(–CH<sub>2</sub>CH<sub>2</sub>O–)<sub>n</sub>–H

[[Chemistry:Trimethylamine|Trimethylamine]] reacts with ethylene oxide in the presence of water, forming [[Chemistry:Choline|choline]]:<ref>{{cite book
|author1=Petrov, AA |author2=Balian HV |author3=Troshchenko AT | chapter= Chapter 12. Amino alcohol| title = Organic chemistry| editor= Stadnichuk| edition = 5|location = St. Petersburg| year = 2002| page = 286| isbn = 5-8194-0067-4}}</ref>

: (CH<sub>2</sub>CH<sub>2</sub>)O + (CH<sub>3</sub>)<sub>3</sub>N + H<sub>2</sub>O → [HOCH<sub>2</sub>CH<sub>2</sub>N (CH<sub>3</sub>)<sub>3</sub>]<sup>+</sup>OH<sup>−</sup>

Aromatic primary and secondary amines also react with ethylene oxide, forming the corresponding arylamino alcohols.

===Halide addition===
Ethylene oxide readily reacts with aqueous solutions of [[Chemistry:Hydrochloric acid|hydrochloric]], [[Chemistry:Hydrobromic acid|hydrobromic]] and [[Chemistry:Hydroiodic acid|hydroiodic acid]]s to form [[Chemistry:Halohydrin|halohydrin]]s. The reaction occurs easier with the last two acids:

: (CH<sub>2</sub>CH<sub>2</sub>)O + HCl → HO–CH<sub>2</sub>CH<sub>2</sub>–Cl

The reaction with these acids competes with the acid-catalyzed hydration of ethylene oxide; therefore, there is always a by-product of ethylene glycol with an admixture of [[Chemistry:Diethylene glycol|diethylene glycol]]. For a cleaner product, the reaction is conducted in the gas phase or in an organic solvent.

Ethylene fluorohydrin is obtained differently, by boiling [[Chemistry:Hydrogen fluoride|hydrogen fluoride]] with a 5–6% solution of ethylene oxide in [[Chemistry:Diethyl ether|diethyl ether]]. The ether normally has a water content of 1.5–2%; in absence of water, ethylene oxide polymerizes.<ref>{{cite book|author1=Sheppard, William A.  |author2=Sharts, Clay M.| title = Organic Fluorine Chemistry|url=https://archive.org/details/organicfluorinec0000shep |url-access=registration |publisher = W. A. Benjamin| year = 1969| page= 98| isbn = 0-8053-8790-0}}</ref>

Halohydrins can also be obtained by passing ethylene oxide through aqueous solutions of metal halides:<ref name="oe3" />

:2 (CH<sub>2</sub>CH<sub>2</sub>)O + CuCl<sub>2</sub> + 2 H<sub>2</sub>O → 2 HO–CH<sub>2</sub>CH<sub>2</sub>–Cl + Cu(OH)<sub>2</sub>↓

===Metalorganic addition===
Interaction of ethylene oxide with organomagnesium compounds, which are [[Chemistry:Grignard reaction|Grignard reagents]], can be regarded as [[Chemistry:Nucleophilic substitution|nucleophilic substitution]] influenced by [[Chemistry:Carbanion|carbanion]] organometallic compounds. The final product of the reaction is a primary alcohol:

: <chem>(CH2CH2)O{} + RMgBr -> R-CH2CH2-OMgBr ->[\ce{H2O}]
\overset{primary~alcohol}{R-CH2CH2-OH}</chem>

Similar mechanism is valid for other organometallic compounds, such as alkyl lithium:

: <chem>(CH2CH2)O{} + \overset{alkyl~lithium}{RLi} -> R-CH2CH2-OLi ->[\ce{H2O}] R-CH2CH2-OH</chem>

===Other addition reactions===
====Addition of hydrogen cyanide====
Ethylene oxide easily reacts with [[Chemistry:Hydrogen cyanide|hydrogen cyanide]] forming ethylene cyanohydrin:

: (CH<sub>2</sub>CH<sub>2</sub>)O + HCN → HO–CH<sub>2</sub>CH<sub>2</sub>–CN

A slightly chilled (10–20&nbsp;°C) aqueous solution of [[Chemistry:Calcium cyanide|calcium cyanide]] can be used instead of HCN:<ref>{{OrgSynth| author=Kendall, E. C. and McKenzie, B.| year=1923| title=o-Chloromercuriphenol| volume=3| pages=57| prep=cv1p0256}}</ref>

:2 (CH<sub>2</sub>CH<sub>2</sub>)O + Ca(CN)<sub>2</sub> + 2 H<sub>2</sub>O → 2 HO–CH<sub>2</sub>CH<sub>2</sub>–CN + Ca(OH)<sub>2</sub>

Ethylene cyanohydrin easily loses water, producing [[Chemistry:Acrylonitrile|acrylonitrile]]:

:HO–CH<sub>2</sub>CH<sub>2</sub>–CN → CH<sub>2</sub>=CH–CN + H<sub>2</sub>O

====Addition of hydrogen sulfide and mercaptans====
When reacting with the [[Chemistry:Hydrogen sulfide|hydrogen sulfide]], ethylene oxide forms [[Chemistry:2-Mercaptoethanol|2-mercaptoethanol]] and [[Chemistry:Thiodiglycol|thiodiglycol]], and with alkylmercaptans it produces 2-alkyl mercaptoetanol:

: (CH<sub>2</sub>CH<sub>2</sub>)O + H<sub>2</sub>S → HO–CH<sub>2</sub>CH<sub>2</sub>–HS

:2 (CH<sub>2</sub>CH<sub>2</sub>)O + H<sub>2</sub>S → (HO–CH<sub>2</sub>CH<sub>2</sub>)<sub>2</sub>S

: (CH<sub>2</sub>CH<sub>2</sub>)O + RHS → HO–CH<sub>2</sub>CH<sub>2</sub>–SR

The excess of ethylene oxide with an aqueous solution of hydrogen sulfide leads to the tris-(hydroxyethyl) sulfonyl hydroxide:

:3 (CH<sub>2</sub>CH<sub>2</sub>)O + H<sub>2</sub>S → [(HO–CH<sub>2</sub>CH<sub>2</sub>)<sub>3</sub>S<sup>+</sup>]OH<sup>−</sup>

====Addition of nitrous and nitric acids====
Reaction of ethylene oxide with aqueous solutions of [[Chemistry:Barium nitrite|barium nitrite]], [[Chemistry:Calcium nitrite|calcium nitrite]], magnesium nitrite, zinc nitrite or [[Chemistry:Sodium nitrite|sodium nitrite]] leads to the formation of 2-nitroethanol:<ref>{{OrgSynth| author=Noland, Wayland E.| prep=CV5P0833| title = 2-Nitroethanol|volume=5|pages=833|year=1973}}</ref>

:2 (CH<sub>2</sub>CH<sub>2</sub>)O + Ca(NO<sub>2</sub>)<sub>2</sub> + 2 H<sub>2</sub>O → 2 HO–CH<sub>2</sub>CH<sub>2</sub>–NO<sub>2</sub> + Ca(OH)<sub>2</sub>

With [[Chemistry:Nitric acid|nitric acid]], ethylene oxide forms mono- and [[Chemistry:Ethylene glycol dinitrate|dinitroglycols]]:<ref>{{cite book| author = Orlova, EY| title = Chemistry and technology of high explosives: Textbook for high schools| edition = 3| publisher = Khimiya| year = 1981| page= 278}}</ref>

: <chem>(CH2CH2)O{} + \overset{nitric\atop acid}{HNO3} -> HO-CH2CH2-ONO2 ->[\ce{+HNO3}] [\ce{-H2O}] O2NO-CH2CH2-ONO_2</chem>

====Reaction with compounds containing active methylene groups====
In the presence of [[Chemistry:Alkoxide|alkoxides]], reactions of ethylene oxide with compounds containing active methylene group leads to the formation of [[Chemistry:Gamma-Butyrolactone|butyrolactones]]:<ref>{{cite book| author = Vogel, A. I.|title = Vogel's Textbook of practical organic chemistry| url = https://archive.org/details/Vogels_Textbook_of_Practical_Organic_Chemistry_5ed_1989_Longman_WW| edition = 5|location = UK| publisher = Longman Scientific & Technical| year = 1989| page = 1088| isbn = 0-582-46236-3}}</ref>

: [[File:2-ACETYLBUTYROLACTONE-SYNTHESIS.png|550px|Synthesis of 2-acetylbutyrolactone]]

====Alkylation of aromatic compounds====
Ethylene oxide enters into the [[Chemistry:Friedel–Crafts reaction|Friedel–Crafts reaction]] with benzene to form [[Chemistry:Phenethyl alcohol|phenethyl alcohol]]:

: [[File:Oxirane+benzene.png|400px|Friedel-Crafts reaction with ethylene oxide]]

[[Chemistry:Styrene|Styrene]] can be obtained in one stage if this reaction is conducted at elevated temperatures ({{Convert|315–440|C|}}) and pressures ({{Convert|0.35–0.7|MPa||abbr=on}}), in presence of an aluminosilicate catalyst.<ref>Watson, James M. and Forward, Cleve (17 April 1984) "Reaction of benzene with ethylene oxide to produce styrene" {{US Patent|4443643}}</ref>

====Synthesis of crown ethers====
A series of polynomial [[Chemistry:Heterocyclic compound|heterocyclic compound]]s, known as [[Chemistry:Crown ether|crown ether]]s, can be synthesized with ethylene oxide. One method is the cationic cyclopolymerization of ethylene oxide, limiting the size of the formed cycle:<ref name="crown">{{cite book| author = Hiraoka M.| title = Crown Compounds. TheirCharacteristics and Applications| publisher = Kodansha| year = 1982| pages= 33–34| isbn =4-06-139444-4}}</ref>

:''n'' (CH<sub>2</sub>CH<sub>2</sub>)O → (–CH<sub>2</sub>CH<sub>2</sub>–O–)<sub>''n''</sub>

To suppress the formation of other linear polymers the reaction is carried out in a highly dilute solution.<ref name="crown" />

Reaction of ethylene oxide with [[Chemistry:Sulfur dioxide|sulfur dioxide]] in the presence of caesium salts leads to the formation of an 11-membered heterocyclic compound which has the complexing properties of crown ethers:<ref name="autogenerated1">{{cite journal| author = H. W. Roesky|author2= H. G. Schmidt| title = Reaction of Ethylene Oxide with Sulfur Dioxide in the Presence of Cesium Ions: Synthesis of 1,3,6,9,2 λ <sup>4</sup>-Tetraoxathia-2-cycloundecanone| journal = Angewandte Chemie International Edition| year = 1985|doi=10.1002/anie.198506951| volume = 24| page = 695| issue = 8}}</ref>

: [[File:Tetraoxathia-2-cycloundecanone.png|350px]]

===Isomerization===
When heated to about {{Convert|400|C||sigfig=2}}, or to {{Convert|150–300|C||sigfig=2}} in the presence of a catalyst ([[Chemistry:Aluminium oxide|Al<sub>2</sub>O<sub>3</sub>]], [[Chemistry:Phosphoric acid|H<sub>3</sub>PO<sub>4</sub>]], etc.), ethylene oxide  [[Chemistry:Isomerization|isomerizes]] into [[Chemistry:Acetaldehyde|acetaldehyde]]:<ref name="petrov">{{cite book
|author1=Petrov, AA |author2=Balian HV |author3=Troshchenko AT | chapter= Chapter 4. Ethers
| title = Organic chemistry| edition=5
| location = St. Petersburg.
| year = 2002
| pages = 159–160
| isbn = 5-8194-0067-4}}</ref>

: <chem>(CH2CH2)O ->[\ce{200^\circ C}] [\ce{Al2O3}] \overset{acetaldehyde}{CH3CHO}</chem>

The radical mechanism was proposed to explain this reaction in the gas phase; it comprises the following stages:<ref name="benson">{{cite journal
| author = Benson S. W.
| title = Pyrolysis of Ethylene Oxide. A Hot Molecule Reaction
| doi=10.1063/1.1729851| journal = The Journal of Chemical Physics
| year = 1964
| volume = 40
| issue = 1
| page = 105
| bibcode = 1964JChPh..40..105B
}}</ref>

{{NumBlk|:| (CH<sub>2</sub>CH<sub>2</sub>)O ↔ •CH<sub>2</sub>CH<sub>2</sub>O• → CH<sub>3</sub>CHO*|{{EquationRef|1}}}}

{{NumBlk|:| CH<sub>3</sub>CHO* → CH<sub>3</sub>• + CHO•|{{EquationRef|2}}}}

{{NumBlk|:| CH<sub>3</sub>CHO* + M → CH<sub>3</sub>CHO + M*|{{EquationRef|3}}}}

In reaction ({{EquationNote|3}}), '''M''' refers to the wall of the reaction vessel or to a heterogeneous catalyst.
The moiety CH<sub>3</sub>CHO* represents a short-lived (lifetime of 10<sup>−8.5</sup> seconds), activated molecule of acetaldehyde. Its excess energy is about 355.6 kJ/mol, which exceeds by 29.3 kJ/mol the [[Physics:Binding energy|binding energy]] of the C-C bond in acetaldehyde.<ref name="benson" />

In absence of a catalyst, the thermal isomerization of ethylene oxide is never selective and apart from acetaldehyde yields significant amount of by-products (see section Thermal decomposition).<ref name="oe2"/>

===Reduction reaction===
Ethylene oxide can be hydrogenated into ethanol in the presence of a catalyst, such as [[Chemistry:Nickel|nickel]], [[Chemistry:Platinum|platinum]], [[Chemistry:Palladium|palladium]],<ref name="oe2" /> [[Chemistry:Borane|borane]]s, [[Chemistry:Lithium aluminium hydride|lithium aluminium hydride]] and some other [[Physics:Hydride|hydride]]s.<ref name="reduction">{{cite book
| author = Hudlický M.
| title = Reductions in Organic Chemistry
| location = Chichester
| publisher = Ellis Horwood Limited
| year = 1984
| page = 83
| isbn = 0-85312-345-4}}</ref>

: <chem>(CH2CH2)O{} + H2 ->[{}\atop\ce{Ni, Pt, Pd, BH3, LiAlH4}\text{ or other hydrides}] [\ce{80^\circ C}] \underset{ethanol}{C2H5OH}</chem>

Conversely, with some other catalysts, ethylene oxide may be ''reduced'' by hydrogen to ethylene with the yield up to 70%. The reduction catalysts include mixtures of zinc dust and [[Chemistry:Acetic acid|acetic acid]], of lithium aluminium hydride with titanium trichloride (the reducing agent is actually [[Chemistry:Titanium(II) chloride|titanium dichloride]], formed by the reaction between LiAlH<sub>4</sub> and TiCl<sub>3</sub>) and of [[Chemistry:Iron(III) chloride|iron(III) chloride]] with butyllithium in [[Chemistry:Tetrahydrofuran|tetrahydrofuran]].<ref name="reduction" />

: <chem>(CH2CH2)O{} + H2 ->[{}\atop\ce{{Zn} + CH3COOH}] \underset{ethylene}{CH2=CH2} + H2O</chem>

===Oxidation===
Ethylene oxide can further be oxidized, depending on the conditions, to [[Chemistry:Glycolic acid|glycolic acid]] or [[Chemistry:Carbon dioxide|carbon dioxide]]:

: <chem>(CH2CH2)O{} + O2 ->[\ce{AgNO3}] \overset{glycolic\ acid}{HOCH2CO2H}</chem>

Deep gas-phase reactor oxidation of ethylene oxide at {{Convert|800-1000|K|}} and a pressure of {{Convert|0.1–1|MPa||abbr=on}} yields a complex mixture of products containing O<sub>2</sub>, H<sub>2</sub>, [[Chemistry:Carbon monoxide|CO]], [[Chemistry:Carbon dioxide|CO<sub>2</sub>]], [[Chemistry:Methane|CH<sub>4</sub>]], [[Chemistry:Acetylene|C<sub>2</sub>H<sub>2</sub>]], [[Chemistry:Ethylene|C<sub>2</sub>H<sub>4</sub>]], [[Chemistry:Ethane|C<sub>2</sub>H<sub>6</sub>]], [[Chemistry:Propylene|C<sub>3</sub>H<sub>6</sub>]], [[Chemistry:Propane|C<sub>3</sub>H<sub>8</sub>]] and [[Chemistry:Acetaldehyde|CH<sub>3</sub>CHO]].<ref>{{cite journal
| author = Dagaut P.|author2= Voisin D.|author3= Cathonnet M.|author4= Mcguinness M.|author5= Simmie J. M.
| title = The oxidation of ethylene oxide in a jet-stirred reactor and its ignition in shock waves
| journal = Combustion and Flame
| year = 1996
| volume = 156
|issue= 1–2| pages = 62–68
| doi = 10.1016/0010-2180(95)00229-4
}}</ref>

===Dimerization===
In the presence of acid catalysts, ethylene oxide dimerizes to afford dioxane:

: [[File:Dioxane-synthesis.png|250px|Synthesis of dioxane]]

The reaction mechanism is as follows:<ref name="oe2" />

: [[File:Dioxan-HerstellungCZ.png|650px|Mechanism of dimerization]]

The dimerization reaction is unselective.  By-products include [[Chemistry:Acetaldehyde|acetaldehyde]] (due to isomerization). The selectivity and speed of dimerization can be increased by adding a catalyst, such as platinum, platinum-palladium, or [[Chemistry:Iodine|iodine]] with [[Chemistry:Sulfolane|sulfolane]]. 2-methyl-1,3-[[Chemistry:Dioxolane|dioxolane]] is formed as a side product in the last case.<ref>Stapp, Paul R. (21 December 1976) "Cyclodimerization of ethylene oxide" {{US Patent|3998848}}</ref>

===Polymerization===
Liquid ethylene oxide can form [[Chemistry:Polyethylene glycol|polyethylene glycol]]s. The polymerization can proceed via radical and ionic mechanisms, but only the latter has a wide practical application.<ref name="glycol">{{cite book
|author1=Dyment, ON |author2=Kazanskii, KS |author3=Miroshnikov AM | title = Гликоли и другие производные окисей этилена и пропилена|trans-title=Glycols and other derivatives of ethylene oxide and propylene
| editor = Dyment, ON
| publisher = Khimiya
| year = 1976
| pages = 214–217}}</ref> [[Chemistry:Cationic polymerization|Cationic polymerization]] of ethylene oxide is assisted by protic acids ([[Chemistry:Perchloric acid|HClO<sub>4</sub>]], [[Chemistry:Hydrochloric acid|HCl]]), Lewis acids ([[Chemistry:Tin(IV) chloride|SnCl<sub>4</sub>]], [[Chemistry:Boron trifluoride|BF<sub>3</sub>]], etc.), organometallic compounds, or more complex reagents:<ref name="glycol" />

: <math chem>n\ce{(CH2CH2)O ->[\ce{SnCl4}]}\ \overbrace{\ce{(CH2CH2-O-)}_n}^\ce{polyethyleneglycol}</math>

The reaction mechanism is as follows.<ref name="poly">{{cite book
| title = Polymeric materials encyclopedia
| editor= Salamone, Joseph C.
| publisher = CRC Press
| year = 1996
| volume = 8
| pages = 6036–6037
| isbn = 978-0-8493-2470-3}}</ref> At the first stage, the catalyst (MX<sub>m</sub>) is initiated by alkyl-or acylhalogen or by compounds with active hydrogen atoms, usually water, alcohol or glycol:

:MX<sub>m</sub> + ROH → MX<sub>m</sub>RO<sup>−</sup>H<sup>+</sup>

The resulting active complex reacts with ethylene oxide via the '''S<sub>N</sub>2''' mechanism:

: (CH<sub>2</sub>CH<sub>2</sub>)O + MX<sub>m</sub>RO<sup>−</sup>H<sup>+</sup> → (CH<sub>2</sub>CH<sub>2</sub>)O•••H<sup>+</sup>O<sup>−</sup>RMX<sub>m</sub>

: (CH<sub>2</sub>CH<sub>2</sub>)O•••H<sup>+</sup> O<sup>−</sup>RMX<sub>m</sub> → HO–CH<sub>2</sub>CH<sub>2</sub><sup>+</sup> + MX<sub>m</sub>RO<sup>−</sup><sub>2</sub>

:HO–CH<sub>2</sub>CH<sub>2</sub><sup>+</sup> + n (CH<sub>2</sub>CH<sub>2</sub>)O → HO–CH<sub>2</sub>CH<sub>2</sub>–(O–CH<sub>2</sub>CH<sub>2</sub>)<sub>n</sub><sup>+</sup>

The chain breaks as

:HO–CH<sub>2</sub>CH<sub>2</sub>–(O–CH<sub>2</sub>CH<sub>2</sub>)<sub>n</sub><sup>+</sup> + MX<sub>m</sub>RO<sup>−</sup> → HO–CH<sub>2</sub>CH<sub>2</sub>–(O–CH<sub>2</sub>CH<sub>2</sub>)<sub>n</sub>–OR + MX<sub>m</sub>

:H(O–CH<sub>2</sub>CH<sub>2</sub>)<sub>n</sub>–O–CH<sub>2</sub>–CH<sub>2</sub><sup>+</sup> + MX<sub>m</sub>RO<sup>−</sup> → H(O–CH<sub>2</sub>CH<sub>2</sub>)<sub>n</sub>–O–CH=CH<sub>2</sub> + MX<sub>m</sub> + ROH

Anionic polymerization of ethylene oxide is assisted by bases, such as [[Chemistry:Alkoxide|alkoxide]]s, [[Chemistry:Hydroxide|hydroxide]]s, [[Chemistry:Carbonate|carbonate]]s or other compounds of alkali or [[Chemistry:Alkaline earth metal|alkaline earth metal]]s.<ref name="glycol" /> The reaction mechanism is as follows:<ref name="poly" />

: (CH<sub>2</sub>CH<sub>2</sub>)O + RONa → RO–CH<sub>2</sub>CH<sub>2</sub>–O<sup>−</sup>Na<sup>+</sup>

:RO–CH<sub>2</sub>CH<sub>2</sub>–O<sup>−</sup>Na<sup>+</sup> + n (CH<sub>2</sub>CH<sub>2</sub>)O → RO–(CH<sub>2</sub>CH<sub>2</sub>–O)<sub>n</sub>–CH<sub>2</sub>CH<sub>2</sub>–O<sup>−</sup>Na<sup>+</sup>

:RO–(CH<sub>2</sub>CH<sub>2</sub>–O)<sub>n</sub>–CH<sub>2</sub>CH<sub>2</sub>–O<sup>−</sup>Na<sup>+</sup> → RO–(CH<sub>2</sub>CH<sub>2</sub>–O)<sub>n</sub>–CH=CH<sub>2</sub> + NaOH

:RO–(CH<sub>2</sub>CH<sub>2</sub>–O)<sub>n</sub>–CH<sub>2</sub>CH<sub>2</sub>–O<sup>−</sup>Na<sup>+</sup> + H<sub>2</sub>O → RO–(CH<sub>2</sub>CH<sub>2</sub>–O)<sub>(n+1)</sub>OH + NaOH

===Thermal decomposition===
Ethylene oxide is relatively stable to heating – in the absence of a catalyst, it does not dissociate up to {{Convert|300|C|}}, and only above {{Convert|570|C|}} there is a major exothermic decomposition, which proceeds through the radical mechanism.<ref name="oe2">{{cite book
| chapter= Chapter II. Chemical properties of ethylene oxide
| title = Ethylene oxide
|editor1=Zimakov, P.V. |editor2=Dyment, O. H. | publisher = Khimiya
| year = 1967
| pages = 57–85}}</ref> The first stage involves isomerization, however high temperature accelerates the radical processes. They result in a gas mixture containing acetaldehyde, ethane, ethyl, methane, hydrogen, carbon dioxide, [[Chemistry:Ketene|ketene]] and [[Physics:Formaldehyde|formaldehyde]].<ref>{{cite journal
| author = Neufeld L.M.|author2= Blades A.T.
| title = The Kinetics of the Thermal Reactions of Ethylene Oxide
| journal = Canadian Journal of Chemistry
| year = 1963|doi=10.1139/v63-434
| volume = 41
| pages = 2956–2961
| issue = 12| doi-access = 
}}</ref> High-temperature [[Chemistry:Pyrolysis|pyrolysis]] ({{Convert|830–1200|K|}}) at elevated pressure in an inert atmosphere leads to a more complex composition of the gas mixture, which also contains [[Chemistry:Acetylene|acetylene]] and [[Chemistry:Propane|propane]].<ref name="Lifshitz">{{cite journal|author = Lifshitz A.|author2= Ben-Hamou H.
| title = Thermal reactions of cyclic ethers at high temperatures. 1. Pyrolysis of ethylene oxide behind reflected shocks
| journal = The Journal of Physical Chemistry
| year = 1983|doi=10.1021/j100233a026
| volume = 87
| pages = 1782–1787|issue = 10
}}</ref> Contrary to the isomerization, initiation of the chain occurs mainly as follows:<ref name="Lifshitz" />

: (CH<sub>2</sub>CH<sub>2</sub>)O → •CH<sub>2</sub>CH<sub>2</sub>O• → CH<sub>2</sub>O + CH<sub>2</sub>:

When carrying the thermal decomposition of ethylene oxide in the presence of transition metal compounds as catalysts, it is possible not only to reduce its temperature, but also to have [[Chemistry:Ethyl group|ethyl]] as the main product, that is to reverse the ethylene oxide synthesis reaction.

=== Other reactions ===
[[Chemistry:Thiocyanate|Thiocyanate]] ions or [[Chemistry:Thiourea|thiourea]] transform ethylene oxide into [[Chemistry:Thiirane|thiirane]] (ethylene sulfide):<ref>{{cite book
| author = Gilchrist T.
| title = Heterocyclic Chemistry
| publisher = Pearson Education
| year = 1985
| pages = 411–412
| isbn = 81-317-0793-8}}</ref>

: (CH<sub>2</sub>CH<sub>2</sub>)O + (NH<sub>2</sub>)<sub>2</sub>C=S → (CH<sub>2</sub>CH<sub>2</sub>)S + (NH<sub>2</sub>)<sub>2</sub>C=O

: [[File:Thiirane-synthesis.png|550px|mechanism synthesis thiiranes of ethylene oxide under the influence of thiocyanate ion]]

Reaction of [[Chemistry:Phosphorus pentachloride|phosphorus pentachloride]] with ethylene oxide produces ethylene dichloride:<ref name="oe3" />

: (CH<sub>2</sub>CH<sub>2</sub>)O + PCl<sub>5</sub> → Cl–CH<sub>2</sub>CH<sub>2</sub>–Cl + POCl<sub>3</sub>

Other dichloro derivatives of ethylene oxide can be obtained by combined action of [[Chemistry:Sulfuryl chloride|sulfuryl chloride]] (SOCl<sub>2</sub>) and [[Chemistry:Pyridine|pyridine]] and of [[Chemistry:Triphenylphosphine|triphenylphosphine]] and [[Chemistry:Carbon tetrachloride|carbon tetrachloride]].<ref name="march2">
{{cite book
|author1=Smith, Michael B.  |author2=March, Jerry
| title = Advanced organic chemistry. Reactions, Mechanisms and Structure
| publisher = Wiley-Interscience
| year = 2007|url=https://books.google.com/books?id=JDR-nZpojeEC
| isbn =978-0-471-72091-1}}</ref>

[[Chemistry:Phosphorus trichloride|Phosphorus trichloride]] reacts with ethylene oxide forming chloroethyl esters of phosphorous acid:<ref name="oe3" />

: (CH<sub>2</sub>CH<sub>2</sub>)O + PCl<sub>3</sub> → Cl–CH<sub>2</sub>CH<sub>2</sub>–OPCl<sub>2</sub>

:2 (CH<sub>2</sub>CH<sub>2</sub>)O + PCl<sub>3</sub> → (Cl–CH<sub>2</sub>CH<sub>2</sub>–O)<sub>2</sub>PCl

:3 (CH<sub>2</sub>CH<sub>2</sub>)O + PCl<sub>3</sub> → Cl–CH<sub>2</sub>CH<sub>2</sub>–O)<sub>3</sub>P

The reaction product of ethylene oxide with [[Chemistry:Acyl chloride|acyl chloride]]s in the presence of [[Chemistry:Sodium iodide|sodium iodide]] is a complex iodoethyl ester:<ref name="march2" />

: (CH<sub>2</sub>CH<sub>2</sub>)O + RCOCl + NaI → RC(O)–OCH<sub>2</sub>CH<sub>2</sub>–I + NaCl

Heating ethylene oxide to 100&nbsp;°C with [[Chemistry:Carbon dioxide|carbon dioxide]], in a non-polar solvent in the presence of ''bis''-(triphenylphosphine)-nickel(0) results in [[Chemistry:Ethylene carbonate|ethylene carbonate]]:<ref>{{cite book |author1    = Fieser, L.
 |author2    = Fieser, M.
 |title      = Reagents for Organic Synthesis
 |publisher  = Wiley
 |volume     = 7
 |year       = 1979
 |page       = [https://archive.org/details/reagentsfororgan07fies_0/page/545 545]
 |isbn       = 978-0-471-02918-2
 |url-access = registration
 |url        = https://archive.org/details/reagentsfororgan07fies_0/page/545
}}</ref>

: [[File:Ethylene-carbonate-syn.png|380px|Synthesis of ethylene carbonate]]

In industry, a similar reaction is carried out at high pressure and temperature in the presence of quaternary ammonium or phosphonium salts as a catalyst.<ref>{{cite book
| author = Sheldon RA
| title= Chemicals from synthesis gas: catalytic reactions of CO and, Volume 2
| url=https://books.google.com/books?id=s1_rjRUlu1EC&pg=PA193|page=193
| publisher = Springer
| year = 1983
| isbn=90-277-1489-4}}</ref>

Reaction of ethylene oxide with [[Physics:Formaldehyde|formaldehyde]] at 80–150&nbsp;°C in the presence of a catalyst leads to the formation of [[Chemistry:Dioxolane|1,3-dioxolane]]:<ref name="fiser">{{cite book
|author1=Fieser, L.  |author2=Fieser, M.
| title = Reagents for Organic Synthesis
| publisher = Wiley
| year = 1977|isbn=978-0-471-25873-5
| volume = 6
| page= 197}}</ref>

: [[File:Dioxolane.png|330px|Synthesis of 1,3-dioxolane]]

Substituting formaldehyde by other aldehydes or ketones results in a 2-substituted 1,3-dioxolane (yield: 70–85%, catalyst: tetraethylammonium bromide).<ref name="fiser" />

Catalytic [[Chemistry:Hydroformylation|hydroformylation]] of ethylene oxide gives hydroxypropanal which can be hydrogenated to propane-1,3-diol:<ref>Han, Yuan-Zhang and Viswanathan, Krishnan (13 February 2003) "Hydroformylation of ethylene oxide" {{US Patent|20030032845}}</ref>

: <chem>(CH2CH2)O + CO + H2 -> CHO-CH2CH2-OH ->[\ce{+H2}] HO-CH2CH2CH2-OH</chem>

==Laboratory synthesis==

===Dehydrochlorination of ethylene and its derivatives===
Dehydrochlorination of 2-chloroethanol, developed by Wurtz  in 1859, remains a common laboratory route to ethylene oxide:

:<chem>Cl-CH2CH2-OH + NaOH -> (CH2CH2)O + NaCl + H2O</chem>

The reaction is carried out at elevated temperature, and beside [[Chemistry:Sodium hydroxide|sodium hydroxide]] or [[Chemistry:Potassium hydroxide|potassium hydroxide]], [[Chemistry:Calcium hydroxide|calcium hydroxide]], [[Chemistry:Barium hydroxide|barium hydroxide]], [[Chemistry:Magnesium hydroxide|magnesium hydroxide]] or [[Chemistry:Carbonate|carbonate]]s of alkali or alkaline earth metals can be used.<ref name="oe5">{{cite book
| chapter= Chapter V. Producing ethylene oxide through ethylene
| title = Ethylene oxide
|editor1=Zimakov, P.V. |editor2=Dyment, O. H. | publisher = Khimiya
| year = 1967
| pages = 155–182}}</ref>

With a high yield (90%) ethylene oxide can be produced by treating [[Chemistry:Calcium oxide|calcium oxide]] with ethyl hypochlorite; substituting calcium by other alkaline earth metals reduces the reaction yield:<ref name="oeII">{{cite book
| chapter = Part II. Synthesis of ethylene oxide. Overview of reactions of formation of ethylene oxide and other α-oxides
| title = Ethylene oxide
|editor1=Zimakov, P.V. |editor2=Dyment, O. H. | publisher = Khimiya
| year = 1967
| pages = 145–153}}</ref>

:<chem>2 CH3CH2-OCl + CaO -> 2 (CH2CH2)O + CaCl2 + H2O</chem>

===Direct oxidation of ethylene by peroxy acids===
Ethylene can be directly oxidized into ethylene oxide using [[Chemistry:Peroxy acid|peroxy acid]]s, for example, [[Chemistry:Peroxybenzoic acid|peroxybenzoic]] or ''meta''-chloro-peroxybenzoic acid:<ref>{{cite book
| author = McMurry J.
| title = Organic chemistry
| edition = 7
| publisher = Thomson
| year = 2008
| page= 661
| isbn = 978-0-495-11258-7}}</ref>

: [[File:Epoxides-synthesis.png|500px|Oxidation of ethylene by peroxy acids]]

Oxidation by peroxy acids is efficient for higher alkenes, but not for ethylene. The above reaction is slow and has low yield, therefore it is not used in the industry.<ref name="oeII" />

===Other preparative methods===
Other synthesis methods include<ref name="oeII" /> reaction of diiodo ethane with [[Chemistry:Silver oxide|silver oxide]]:
:<chem>I-CH2CH2-I + Ag2O -> (CH2CH2)O + 2AgI</chem>

and decomposition of [[Chemistry:Ethylene carbonate|ethylene carbonate]] at {{Convert|200–210|C|}} in the presence of [[Chemistry:Hexachloroethane|hexachloroethane]]:

: [[File:Ethylenecarbonate-decomposition.png|350px|Decomposition of ethylene carbonate]]

==Industrial synthesis==

===History===
Commercial production of ethylene oxide dates back to 1914 when BASF built the first factory which used the chlorohydrin process (reaction of ethylene chlorohydrin with calcium hydroxide). The chlorohydrin process was unattractive for several reasons, including low efficiency and loss of valuable chlorine into [[Chemistry:Calcium chloride|calcium chloride]].<ref>{{cite journal
| author = Norris, J.F.
| title = The Manufacture of War Gases in Germany
| journal = Journal of Industrial and Engineering Chemistry
| year = 1919
| volume = 11
| pages = 817–829
| doi = 10.1021/ie50117a002
| issue = 9| url = https://zenodo.org/record/1428740
}}</ref> More efficient direct oxidation of ethylene by air was invented by Lefort in 1931 and in 1937 Union Carbide opened the first plant using this process. It was further improved in 1958 by Shell Oil Co. by replacing air with oxygen and using elevated temperature of {{Convert|200–300|C||sigfig=2}} and pressure ({{Convert|1–3|MPa||abbr=on}}).<ref name = "industrial"/> This more efficient route accounted for about half of ethylene oxide production in the 1950s in the US, and after 1975 it completely replaced the previous methods.<ref name = "industrial" >{{cite book
|author1=Weissermel K. |author2=Arpe H-J. | title = Industrial organic chemistry
| edition = 4
| location = Weinheim
| publisher = Wiley-VCH
| year = 2003
| pages = 145–148
| isbn = 978-3-527-30578-0}}</ref>
The production of ethylene oxide accounts for approximately 11% of worldwide ethylene demand.<ref>[http://www.ceresana.com/en/market-studies/chemicals/ethylene/ Market Study: Ethylene] {{Webarchive|url=https://web.archive.org/web/20150307115926/http://www.ceresana.com/en/market-studies/chemicals/ethylene/ |date=7 March 2015 }}. Ceresana.com (December 2010). Retrieved on 8 May 2017.</ref>

===Chlorohydrin process of production of ethylene oxide===
Although the chlorohydrin process is almost entirely superseded in the industry by the direct oxidation of ethylene, the knowledge of this method is still important for educational reasons and because it is still used in the production of [[Chemistry:Propylene oxide|propylene oxide]].<ref>{{cite web
| date = February 1985
| url = http://www.sriconsulting.com/PEP/Public/Reports/Phase_84/RP002D/
| title = Process Economics Program Report 2D
| work = PEP Report
| publisher = SRI Consulting
| access-date = 19 November 2009}}</ref> The process consists of three major steps: synthesis of ethylene chlorohydrin, dehydrochlorination of ethylene chlorohydrin to ethylene oxide and purification of ethylene oxide. Those steps are carried continuously. In the first column, hypochlorination of ethylene is carried out as follows:<ref name="uk">{{cite book
| author = Yukelson I.I.
| title = The technology of basic organic synthesis
| publisher = Khimiya
| year = 1968
| pages = 554–559}}</ref>

:Cl<sub>2</sub> + H<sub>2</sub>O → HOCl + HCl

:CH<sub>2</sub>=CH<sub>2</sub> + HOCl → HO–CH<sub>2</sub>CH<sub>2</sub>–Cl

:CH<sub>2</sub>=CH<sub>2</sub> + Cl<sub>2</sub> → Cl–CH<sub>2</sub>CH<sub>2</sub>–Cl

To suppress the conversion of ethylene into the ethylene dichloride (the last reaction), the concentration of ethylene is maintained at about 4–6%, and the solution is heated by steam to the boiling point.<ref name="uk" />

Next, aqueous solution of ethylene chlorohydrin enters the second column, where it reacts with a 30% solution of calcium hydroxide at {{Convert|100|C|}}:<ref name="uk" />

:2 HO–CH<sub>2</sub>CH<sub>2</sub>–Cl + Ca(OH)<sub>2</sub> → 2 (CH<sub>2</sub>CH<sub>2</sub>)O + CaCl<sub>2</sub> + 2H<sub>2</sub>O

The produced ethylene oxide is purified by rectification. The chlorohydrin process allows to reach 95% conversion of ethylene chlorohydrin. The yield of ethylene oxide is about 80% of the theoretical value; for {{Convert|1|t|}} of ethylene oxide, about {{Convert|200|kg||abbr=on}} of ethylene dichloride is produced.<ref name="uk" /> But, the major drawbacks of this process are high chlorine consumption and effluent load. This process is now obsolete.

===Direct oxidation of ethylene===

====Usage in global industry====
Direct oxidation of ethylene was patented by Lefort in 1931. This method was repeatedly modified for industrial use, and at least four major variations are known. They all use oxidation by oxygen or air and a silver-based catalyst, but differ in the technological details and hardware implementations.<ref name="eos">{{cite book
| chapter = Catalitic Oxidation of Olefins
| title = Advances in catalysis and related subjects
|editor1=Eley, D.D. |editor2=Pines, H. |editor3=Weisz, P.B. | location = New York
| publisher = Academic Press Inc
| year = 1967
| volume = 17
| pages = 156–157}}</ref>

Union Carbide (currently a division of [[Company:Dow Chemical Company|Dow Chemical Company]]) was the first company to develop the direct oxidation process.<ref name="cmpa">{{cite book
|author1=Bloch H. P. |author2=Godse A. | title = Compressors and modern process applications|publisher = John Wiley and Sons
| year = 2006
| pages = 295–296
| isbn = 978-0-471-72792-7
}}</ref>

A similar production method was developed by Scientific Design Co., but it received wider use because of the licensing system – it accounts for 25% of the world's production and for 75% of world's licensed production of ethylene oxide.<ref name = "cmpa"/><ref>{{cite web|url=http://www.scidesign.com/Business/EO%20-%20EG%20Process/EO_EG_Process.htm |title=Ethylene Oxide/Ethylene Glycol Process |work=Process Licensing and Engineering |publisher=Scientific Design Company |access-date=3 October 2009 |url-status=dead |archive-url=https://web.archive.org/web/20110716014802/http://www.scidesign.com/Business/EO%20-%20EG%20Process/EO_EG_Process.htm |archive-date=16 July 2011 }}</ref> A proprietary variation of this method is used by Japan Catalytic Chemical Co., which adapted synthesis of both ethylene oxide and ethylene glycol in a single industrial complex.

A different modification was developed Shell International Chemicals BV. Their method is rather flexible with regard to the specific requirements of specific industries; it is characterized by high selectivity with respect to the ethylene oxide product and long lifetime of the catalyst (3 years). It accounts for about 40% of global production.<ref name="cmpa" />

Older factories typically use air for oxidation whereas newer plants and processes, such as METEOR and Japan Catalytic, favor oxygen.<ref>{{cite book
|author1=Chauvel A. |author2=Lefebvre G. | title = Petrochemical processes 2. Major Oxygenated, Chlorinated and Nitrated Derivatives
| edition = 2
| location = Paris
| publisher = Editions Technip
| year = 1989
| volume = 2
| page= 4
| isbn = 2-7108-0563-4}}</ref>

====Chemistry and kinetics of the direct oxidation process====
Formally, the direct oxidation process is expressed by the following equation:

: <chem>2CH_2=CH2 + O2 ->[\ce{Ag}] 2(CH2CH2)O</chem>, ΔH = −105 kJ/mol

However, significant yield of carbon dioxide and water is observed in practice, which can be explained by the complete oxidation of ethylene or ethylene oxide:

: CH<sub>2</sub>=CH<sub>2</sub> + 3 O<sub>2</sub> → 2 CO<sub>2</sub> + 2 H<sub>2</sub>O,     ΔH = −1327{{nbsp}}kJ/mol
: (CH<sub>2</sub>CH<sub>2</sub>)O + 2.5 O<sub>2</sub> → 2 CO<sub>2</sub> + 2 H<sub>2</sub>O, ΔH = −1223{{nbsp}}kJ/mol

According to a kinetic analysis by Kilty and Sachtler, the following reactions describe the pathway leading to EO.  In the first step, a [[Chemistry:Superoxide|superoxide]] (O<sub>2</sub><sup>−</sup>) species is formed:<ref name="kilty">{{cite journal
| author = Kilty P. A.|author2= Sachtler W. M. H.
| title = The Mechanism of the Selective Oxidation of Ethylene to Ethylene Oxide
| doi=10.1080/01614947408079624
| journal = Catalysis Reviews: Science and Engineering
| year = 1974
| volume = 10
| pages = 1–16
}}</ref>
:O<sub>2</sub> + Ag  →  Ag<sup>+</sup>O<sub>2</sub><sup>−</sup>
This species reacts with ethylene
:Ag<sup>+</sup>O<sub>2</sub><sup>−</sup>  +  H<sub>2</sub>C=CH<sub>2</sub>   →   (CH<sub>2</sub>CH<sub>2</sub>)O  +  AgO
The resulting silver oxide then oxidizes ethylene or ethylene oxide to CO<sub>2</sub> and water.  This reaction replenishes the silver catalyst. Thus the overall reaction is expressed as

:7 CH<sub>2</sub>=CH<sub>2</sub> + 6 O<sub>2</sub> → 6 (CH<sub>2</sub>CH<sub>2</sub>)O + 2 CO<sub>2</sub> + 2 H<sub>2</sub>O

and the maximum degree of conversion of ethylene to ethylene oxide is theoretically predicted to be 6/7 or 85.7%,<ref name="kilty" /> although higher yields are achieved in practice.<ref>{{Cite journal|last1=Özbek|first1=M. O.|last2=van Santen|first2=R. A.|date=2013|title=The Mechanism of Ethylene Epoxidation Catalysis|journal=Catalysis Letters|volume=143|issue=2|pages=131–141|doi=10.1007/s10562-012-0957-3|s2cid=95354803}}</ref>

The catalyst for the reaction is metallic silver deposited on various matrixes, including [[Earth:Pumice|pumice]], [[Chemistry:Silica gel|silica gel]], various [[Chemistry:Silicate|silicate]]s and [[Chemistry:Aluminosilicate|aluminosilicate]]s, alumina and [[Chemistry:Silicon carbide|silicon carbide]], and activated by certain additives ([[Chemistry:Antimony|antimony]], [[Chemistry:Bismuth|bismuth]], [[Chemistry:Barium peroxide|barium peroxide]], etc.).<ref name = "lebedev">{{cite book
| author = Lebedev, N.N.
| title = Chemistry and Technology of Basic Organic and Petrochemical Synthesis
| year = 1988
| edition = 4
| publisher = Khimiya
| pages = 420–424
| isbn = 5-7245-0008-6
}}</ref> The process temperature was optimized as {{Convert|220–280|C||sigfig=2}}. Lower temperatures reduce the activity of the catalyst, and higher temperatures promote the complete oxidation of ethylene thereby reducing the yield of ethylene oxide. Elevated pressure of {{Convert|1-3|MPa||abbr=on}} increases the productivity of the catalyst and facilitates absorption of ethylene oxide from the reacting gases.<ref name="lebedev" />

Whereas oxidation by air is still being used, oxygen (> 95% purity) is preferred for several reasons, such as higher molar yield of ethylene oxide (75–82% for oxygen vs. 63–75% for air), higher reaction rate (no gas dilution) and no need of separating nitrogen in the reaction products.<ref name="ect" /><ref>{{cite book
| author = Gunardson H.
| title = Industrial gases in petrochemical processing
| location = New York
| publisher = Marcel Dekker, Inc.
| year = 1998
| pages = 131–132
| isbn = 0-8247-9908-9
}}</ref>

=== Process overview ===
The production of ethylene oxide on a commercial scale is attained with the unification of the following unit processes:
* Main reactor
* Ethylene oxide [[Engineering:Scrubber|scrubber]]
* Ethylene oxide de-sorber
* [[Chemistry:Stripping|Stripping]] and distillation column
* CO<sub>2</sub> scrubber and CO<sub>2</sub> de-scrubber

'''Main Reactor:''' The main reactor consists of thousands of catalyst tubes in bundles. These tubes are generally {{Convert|6|to|15|m|abbr=on|round=5}} long with an inner diameter of {{Convert|20|to|50|mm|abbr=on|1}}. The catalyst packed in these tubes is in the form of spheres or rings of diameter {{Convert|3|to|10|mm|abbr=on}}. The operating conditions of {{Convert|200-300|C||sigfig=2}} with a pressure of {{Convert|1-3|MPa||abbr=on}} prevail in the reactor. To maintain this temperature, the cooling system of the reactor plays a vital role. With the aging of the catalyst, its selectivity decreases and it produces more exothermic side products of CO<sub>2</sub>.

'''Ethylene oxide scrubber:''' After the gaseous stream from the main reactor, containing ethylene oxide (1–2%) and CO<sub>2</sub> (5%), is cooled, it is then passed to the ethylene oxide scrubber. Here, water is used as the scrubbing media which scrubs away majority of ethylene oxide along with some amounts of CO<sub>2</sub>, N<sub>2</sub>, CH<sub>2</sub>=CH<sub>2</sub>, CH<sub>4</sub> and aldehydes (introduced by the recycle stream). Also, a small proportion of the gas leaving the ethylene oxide scrubber (0.1–0.2%) is removed continuously (combusted) to prevent the buildup of inert compounds (N<sub>2</sub>, Ar, and C<sub>2</sub>H<sub>6</sub>), which are introduced as impurities with the reactants.

'''Ethylene oxide de-sorber:''' The aqueous stream resulting from the above scrubbing process is then sent to the ethylene oxide de-sorber. Here, ethylene oxide is obtained as the overhead product, whereas the bottom product obtained is known as the ''glycol bleed''. When ethylene oxide is scrubbed from the recycle gas with an aqueous solution, ethylene glycols (viz. mono-ethylene glycol, di-ethylene glycol and other poly-ethylene glycols) get unavoidably produced. Thus, in-order to prevent them from building up in the system, they are continuously bled off.

'''Stripping and distillation column:''' Here, the ethylene oxide stream is stripped off its low boiling components and then distilled in-order to separate it into water and ethylene oxide.

'''CO<sub>2</sub> scrubber:''' The recycle stream obtained from the ethylene oxide scrubber is compressed and a side-stream is fed to the CO<sub>2</sub> scrubber. Here, CO<sub>2</sub> gets dissolved into the hot aqueous solution of potassium carbonate (i.e., the scrubbing media). The dissolution of CO<sub>2</sub> is not only a physical phenomenon, but a chemical phenomenon as well, for, the CO<sub>2</sub> reacts with potassium carbonate to produce potassium hydrogen carbonate.

: K<sub>2</sub>CO<sub>3</sub> + CO<sub>2</sub> + H<sub>2</sub>O → 2 KHCO<sub>3</sub>

'''CO<sub>2</sub> de-scrubber:''' The above potassium carbonate solution (enriched with CO<sub>2</sub>) is then sent to the CO<sub>2</sub> de-scrubber where CO<sub>2</sub> is de-scrubbed by stepwise (usually two steps) [[Chemistry:Flash evaporation|flashing]]. The first step is done to remove the hydrocarbon gases, and the second step is employed to strip off CO<sub>2</sub>.

===World production of ethylene oxide===
The world production of ethylene oxide was {{Convert|20|Mt|e6ST|abbr=unit}} in 2009,<ref name=dutia/> {{Convert|19|Mt|e6ST|abbr=unit}} in 2008 and {{Convert|18|Mt|e6ST|abbr=unit}} in 2007.<ref name="sri">{{cite web
| date = January 2009
| url = http://www.sriconsulting.com/WP/Public/Reports/eo/
| title = Ethylene Oxide
| work = WP Report
| publisher = SRI Consulting
| access-date = 29 September 2009}}</ref> This places ethylene oxide 14th most produced organic chemical, whereas the most produced one was ethylene with {{Convert|113|Mt|e6ST|abbr=unit}}.<ref>{{cite web
| date = January 2009
| url = http://www.sriconsulting.com/WP/Public/Reports/ethylene/
| title = Ethylene
| work = WP Report
| publisher = SRI Consulting
| access-date = 29 September 2009
}}</ref> SRI Consulting forecasted the growth of consumption of ethylene oxide of 4.4% per year during 2008–2013 and 3% from 2013 to 2018.<ref name="sri" />

In 2004, the global production of ethylene oxide by region was as follows:<ref name="iars" />
{| class="wikitable" style="width:95%;"
 ! Align = "center" width = 40%|Region
 ! Align = "center" width = 30%|Number of major producers
 ! Align = "center" width = 30%|Production, thousand tonnes
|-
 |'''North America'''<br /> {{wipe|United States}}<br /> {{wipe|Canada}}<br /> Mexico
| style="text-align:center;"|<br /> 10<br /> 3<br /> 3
| style="text-align:center;"|<br />4009<br /> 1084<br /> 350
|-
 |'''South America'''<br /> {{wipe|Brazil}}<br /> Venezuela
| style="text-align:center;"|<br /> 2<br /> 1
| style="text-align:center;"|<br />312<br /> 82
|-
 |'''Europe'''<br /> Belgium<br /> {{wipe|France}}<br /> {{wipe|Germany}} <br /> Netherlands<br /> {{wipe|Spain}}<br /> [[Place:Turkey|Turkey]]<br /> {{wipe|United Kingdom}} <br /> [[Place:Eastern Europe|Eastern Europe]]
| style="text-align:center;"|<br /> 2<br /> 1<br /> 4<br /> 2<br /> 1<br /> 1<br /> 1<br /> No data
| style="text-align:center;"|<br />770<br /> 215 <br />995<br /> 460 <br />100<br /> 115<br />300<br /> 950
|-
 |'''Middle East'''<br /> [[Religion:Iran|Iran]]<br /> Kuwait<br /> Saudi Arabia
| style="text-align:center;"|<br /> 2<br /> 1<br /> 2
| style="text-align:center;"|<br /> 201 <br />350<br /> 1781
|-
 |'''Asia'''<br /> {{wipe|China}}<br /> Taiwan<br /> {{wipe|India}}<br /> Indonesia<br /> {{wipe|Japan}}<br /> Malaysia<br /> {{wipe|South Korea}}<br /> [[Place:Singapore|Singapore]]
| style="text-align:center;"|<br /> No data<br /> 4<br /> 2<br /> 1<br /> 4<br /> 1<br /> 3<br /> 1
| style="text-align:center;"|<br /> 1354<br />820<br /> 488 <br />175<br />949<br /> 385 <br />740<br /> 80
 |}

The world's largest producers of ethylene oxide are [[Company:Dow Chemical Company|Dow Chemical Company]] ({{Convert|3-3.5|Mt|e6ST|abbr=unit}} in 2006<ref name="aq">{{cite web
| author = Devanney M. T.
| date = April 2007
| url = http://www.sriconsulting.com/PEP/Public/Reports/Phase_2009/RP2I/
| title = Ethylene Oxide
| work = SEH Peport
| publisher = SRI Consulting
| access-date = 19 November 2009
}}</ref>), Saudi Basic Industries ({{Convert|2000-2500|t|ST}} in 2006<ref name="aq" />), Royal Dutch Shell ({{Convert|1.328|Mt|e6ST|abbr=unit}} in 2008–2009<ref>{{cite web
| url = http://www.m-kagaku.co.jp/english/corporate/index.html
| title = Overview
| publisher = Mitsubishi Chemical Corporation
| access-date = 12 October 2009
| url-status = bot: unknown
| archive-url = https://web.archive.org/web/20170225162257/http://www.m-kagaku.co.jp/english/corporate/index.html
| archive-date = 25 February 2017
| df = dmy-all
}}</ref><ref>{{cite web|url=http://www.shell.com/home/content/chemicals/products_services/our_products/ethylene_oxide_glycols/ethylene_glycols/manufacturing_locations/geismar/ |title=Shell Chemical LP – Geismar, United States of America |work=Manufacturing locations |publisher=Shell Chemicals |access-date=12 October 2009 |url-status=dead |archive-url=https://web.archive.org/web/20101018033052/http://www.shell.com/home/content/chemicals/products_services/our_products/ethylene_oxide_glycols/ethylene_glycols/manufacturing_locations/geismar/ |archive-date=18 October 2010 }}</ref><ref>{{cite web|url=http://www.shell.com/home/content/chemicals/products_services/our_products/ethylene_oxide_glycols/ethylene_glycols/manufacturing_locations/moerdijk/ |title=Shell Nederland Chemie BV – Moerdijk, Netherlands |work=Manufacturing locations |publisher=Shell Chemicals |access-date=12 October 2009 |url-status=dead |archive-url=https://web.archive.org/web/20101018033102/http://www.shell.com/home/content/chemicals/products_services/our_products/ethylene_oxide_glycols/ethylene_glycols/manufacturing_locations/moerdijk/ |archive-date=18 October 2010 }}</ref>), BASF ({{Convert|1.175|Mt|e6ST|abbr=unit}} in 2008–2009<ref>{{cite web
| url = http://www.report.basf.com/2008/en/subjects/products/chemicals.html
| title = Segment Chemicals – Products
| date = 28 February 2009
| publisher = BASF
| archive-url = https://web.archive.org/web/20160304223359/http://www.report.basf.com/2008/en/subjects/products/chemicals.html
| access-date = 12 October 2009| archive-date = 4 March 2016
}}</ref>), China Petrochemical Corporation (~{{Convert|1|Mt|e6ST|abbr=unit}} in 2006<ref name="aq" />), Formosa Plastics (~{{Convert|1|Mt|e6ST|abbr=unit}} in 2006<ref name="aq" />) and Ineos ({{Convert|0.92|Mt|e6ST|abbr=unit}} in 2008–2009).<ref>{{cite web|url=http://www.ineosoxide.com/21-Ethylene_Oxide__EO_.htm |title=Ethylene Oxide (EO) |publisher=Ineos Oxide |access-date=12 October 2009 |url-status=dead |archive-url=https://web.archive.org/web/20130608060742/http://www.ineosoxide.com/21-Ethylene_Oxide__EO_.htm |archive-date=8 June 2013 }}</ref>

==Applications==
[[File:Eo-usesEN.png|thumb|350px|Global industrial use of ethylene oxide in 2007.<ref name="iars" />]]

Ethylene oxide is one of the most important raw materials used in  large-scale chemical production. Most ethylene oxide is used for synthesis of [[Chemistry:Ethylene glycol|ethylene glycol]]s, including diethylene glycol and triethylene glycol, that accounts for up to 75% of global consumption. Other important products include ethylene glycol ethers, ethanolamines and ethoxylates. Among glycols, ethylene glycol is used as [[Chemistry:Antifreeze|antifreeze]], in the production of [[Chemistry:Polyester|polyester]] and [[Chemistry:Polyethylene terephthalate|polyethylene terephthalate]] (PET – raw material for plastic bottles), liquid coolants and solvents.

{| class="wikitable"
|-
! Sector !! Demand share (%)
|-
| Agrochemicals || 7
|-
| Oilfield chemicals || 10
|-
| Detergents || 25
|-
| Textile || 35
|-
| Personal care || 10
|-
| Pharmaceuticals || 8
|-
| Others || 5
|-
| Total [2009] || 5.2{{nbsp}}Mt
|}

Polyethyleneglycols are used in perfumes, cosmetics, pharmaceuticals, [[Physics:Lubricant|lubricant]]s, [[Chemistry:Paint thinner|paint thinner]]s and [[Chemistry:Plasticizer|plasticizer]]s. Ethylene glycol ethers are part of brake fluids, detergents, solvents, lacquers and paints. Ethanolamines are used in the manufacture of soap and detergents and for purification of natural gas. Ethoxylates are reaction products of ethylene oxide with higher alcohols, acids or amines. They are used in the manufacture of detergents, surfactants, emulsifiers and [[Chemistry:Dispersant|dispersant]]s.<ref>{{cite web |url=http://www.shell.com/home/content/chemicals/products_services/our_products/ethylene_oxide_glycols/ethylene_glycols/product_overview/ |title=Ethylene oxide product overview |work=Ethylene oxide |publisher=Shell Chemicals |access-date=8 October 2009 |url-status=dead |archive-url=https://web.archive.org/web/20101016145728/http://www.shell.com/home/content/chemicals/products_services/our_products/ethylene_oxide_glycols/ethylene_glycols/product_overview/ |archive-date=16 October 2010 }}</ref>

Whereas synthesis of ethylene glycols is the major application of ethylene oxide, its percentage varies greatly depending on the region: from 44% in the [[Place:Western Europe|Western Europe]], 63% in {{wipe|Japan}} and 73% in [[Earth:North America|North America]] to 90% in the rest of [[Earth:Asia|Asia]] and 99% in [[Earth:Africa|Africa]].<ref>{{cite web
 |url          = http://www.icis.com/v2/chemicals/9075772/ethylene-oxide/uses.html
 |title        = Ethylene Oxide (EO) Uses and Market Data
 |work         = Chemical Intelligence
 |publisher    = Chemical Industry News & Intelligence (ICIS.com)
 |access-date   = 8 October 2009
|archive-url  = https://www.webcitation.org/615sww6sl?url=http://www.icis.com/v2/chemicals/9075772/ethylene-oxide/uses.html
 |archive-date = 21 August 2011
|url-status     = dead
 |df           = dmy-all
}}</ref>

=== Production of ethylene glycol ===
Ethylene glycol is industrially produced by non-catalytic hydration of ethylene oxide at a temperature of {{Convert|200|C|}} and a pressure of {{Convert|1.5-2|MPa||abbr=on}}:<ref name="MEG">{{cite encyclopedia
| chapter= Ethylene
| title = Chemical Encyclopedia
| editor = Knunyants, I. L.
| encyclopedia = Soviet encyclopedia
| year = 1988
| volume = 5
| pages = 984–985
}}</ref>

: <chem>(CH2CH2)O + H2O -> HOCH2CH2OH</chem>

By-products of the reaction are diethylene glycol, triethylene glycol and polyglycols with the total of about 10%, which are separated from the ethylene glycol by distillation at reduced pressure.<ref>{{cite book
| title = Handbook of Detergents, Part F: Production
|editor1=Zoller, Uri |editor2=Sosis, Paul | publisher = CRC Press
| year = 2008
| pages = 518–521
| isbn = 978-0-8247-0349-3
}}</ref>

Another synthesis method is the reaction of ethylene oxide and CO2 (temperature {{Convert|80–120|C|}} and pressure of {{Convert|5.2|MPa||abbr=on}}) yielding [[Chemistry:Ethylene carbonate|ethylene carbonate]] and its subsequent hydrolysis with decarboxylation:<ref name = "MEG" />

: <chem>(CH2CH2)O{} + CO2 -> \overset{ethylene\ carbonate}{(O-CH2CH_2-O)C=O} ->[\ce{+H2O}] [\ce{-CO2}] HOCH2CH2OH</chem>

Modern technologies of production of ethylene glycol include the following.<ref>{{cite web
| author = Naqvi, Syed |date = September 2009
| url = http://www.sriconsulting.com/PEP/Reports/Phase_2009/RP2I/
| title = Process Economics Program Report 2I
| work = PEP Peport
| publisher = SRI Consulting
| access-date = 20 October 2009
}}</ref> Shell OMEGA technology (Only Mono-Ethylene Glycol Advantage) is a two-step synthesis of ethylene carbonate using a [[Physics:Phosphonium|phosphonium]] halide as a catalyst. The glycol yield is 99–99.5%, with other glycols practically absent. The main advantage of the process is production of pure ethylene glycol without the need for further purification. The first commercial plant which uses this method was opened in 2008 in South Korea.<ref>[https://web.archive.org/web/20090514033943/http://www.shell.com/home/content/chemicals/innovation/leading_edge_technology/omega_delivers_ethylene_glycol/omega_delivers_ethylene_glycol.html OMEGA delivers for ethylene glycol makers], Shell (October 2008).</ref> Dow METEOR (Most Effective Technology for Ethylene Oxide Reactions) is an integrated technology for producing ethylene oxide and its subsequent hydrolysis into ethylene glycol. The glycol yield is 90–93%. The main advantage of the process is relative simplicity, using fewer stages and less equipment.

Conversion to ethylene glycol is also the means by which waste ethylene oxide is scrubbed before venting to the environment. Typically the EtO is passed over a matrix containing either sulfuric acid or potassium permanganate.{{citation needed|date=August 2018}}

=== Production of glycol ethers ===
The major industrial esters of mono-, di- and triethylene glycols are methyl, ethyl and normal butyl ethers, as well as their acetates and phthalates. The synthesis involves reaction of the appropriate [[Chemistry:Alcohol|alcohol]] with ethylene oxide:<ref>{{cite book
| title = Encyclopedia of chemical processing and design
|editor1=McKetta, John J. |editor2=Cunningham, William A. | location = New York
| publisher = Marcel Dekker, Inc
| year = 1984
| volume = 20
| pages = 259–260
| isbn = 0-8247-2470-4
}}</ref>

: <chem>(CH2CH2)O + ROH -> HOCH2CH2OR</chem>
: <chem>(CH2CH2)O + HOCH2CH2OR -> HOCH2CH2OCH2CH2OR</chem>
: <chem>(CH2CH2)O + HOCH2CH2OCH2CH2OR -> HOCH2CH2OCH2CH2OCH2CH2OR</chem>

The reaction of monoesters with an acid or its anhydride leads to the formation of the esters:

:<chem>CH3CO2H + HOCH2CH2OR -> ROCH2CH2OCOCH3 + H2O</chem>

=== Production of ethanolamines ===
In the industry, [[Chemistry:Ethanolamine|ethanolamine]]s (mono-, di- and triethanolamines) are produced by reacting [[Chemistry:Ammonia|ammonia]] and ethylene oxide in anhydrous medium at a temperature of {{Convert|40-70|C||-1}} and pressure of {{Convert|1.5-3.5|MPa||abbr=on}}{{nbsp}}MPa:<ref>{{cite web
| url = http://www.himtek.ru/cgi-bin/index.cgi?IdS=18&IdP=9&Lang=0
| title = Technology of ethanolamine
| work = Technology
| publisher = Himtek Engineering
| access-date = 22 October 2009
|archive-url = https://web.archive.org/web/20050302144745/http://www.himtek.ru/cgi-bin/index.cgi?IdS=18&IdP=9&Lang=0 |archive-date = 2 March 2005
}}</ref>

:<chem>(CH2CH2)O + NH3 -> HOCH2CH2NH2</chem>
:<chem>2 (CH2CH2)O + NH3 -> (HOCH2CH2)2NH</chem>
:<chem>3 (CH2CH2)O + NH3 -> (HOCH2CH2)3N</chem>

All three ethanolamines are produced in the process, while ammonia and part of methylamine are recycled. The final products are separated by vacuum [[Distillation|distillation]]. Hydroxyalkylamines are produced in a similar process:

:<chem>(CH2CH2)O + RNH2 -> HOCH2CH2NHR</chem>
:<chem>2 (CH2CH2)O + RNH2 -> (HOCH2CH2)2NR</chem>

Monosubstituted products are formed by reacting a large excess of amine with ethylene oxide in presence of water and at a temperature below {{Convert|100|C|}}. Disubstituted products are obtained with a small excess of ethylene oxide, at a temperature of {{Convert|120–140|C||-1}} and a pressure of {{Convert|0.3-0.5|MPa||abbr=on|round=5}}.<ref>{{cite book
|vauthors=Chekalin MA, Passet BV, Ioffe BA
| title = The technology of organic dyes and intermediate products: A manual for technical
| edition = 2|publisher = Khimiya
| year = 1980
| page= 185
}}</ref><ref><span class="plainlinks">[https://www.cdc.gov/niosh/topics/ethyleneoxide/ Ethylene oxide]</span> NIOSH Workplace Safety and Health Topic. Retrieved 15 October 2012.</ref>

=== Production of ethoxylates ===
{{Main|Chemistry:Ethoxylation}}
<!-- [[File:Alkoxylation process.png|thumb|left|550px|Schematic image of the production ethoxylates <ref name="buss" />]] -->
Industrial production of ethoxylates is realized by a direct reaction of higher alcohols, acids or amines with ethylene oxide in the presence of an alkaline catalyst at a temperature of {{Convert|120–180|C||-1}}. Modern plants producing ethoxylates are usually based on the BUSS LOOP reactors technology,<ref name="buss">{{cite book
| title = Chemistry and technology of surfactants
| editor= Farn, R. J.
| publisher = Blackwell Publishing
| year = 2006
| page = 133
| isbn = 1-4051-2696-5
}}</ref> which is based on a three-stage continuous process. In the first stage, the initiator or catalyst of the reaction and the feedstock are fed into the container, where they are mixed, heated and vacuum dried. Then reaction is carried out in a special insulated reactor in an inert atmosphere (nitrogen) to prevent a possible explosion of ethylene oxide. Finally, the reaction mixture is neutralized, degassed and purified.<ref>{{cite web|url=http://www.buss-ct.com/e/reaction_technology/alkoxylation.php?navid=36 |title=Alkoxylation |work=BUSS LOOP Reactor |publisher=Buss ChemTech AG |access-date=21 October 2009 |url-status=dead |archive-url=https://web.archive.org/web/20120308161412/http://www.buss-ct.com/e/reaction_technology/alkoxylation.php?navid=36 |archive-date=8 March 2012 }}</ref>

=== Production of acrylonitrile ===
Currently, most [[Chemistry:Acrylonitrile|acrylonitrile]] (90% in 2008) is produced by the SOHIO method, which is based on the catalytic oxidation of [[Chemistry:Propylene|propylene]] in the presence of ammonia and bismuth phosphomolybdate. However, until 1960 a key production process was addition of [[Chemistry:Hydrogen cyanide|hydrogen cyanide]] to ethylene oxide, followed by dehydration of the resulting [[Chemistry:Cyanohydrin|cyanohydrin]]:<ref name="ACS Landmarks">{{cite web |url=http://portal.acs.org/portal/PublicWebSite/education/whatischemistry/landmarks/acrylonitrile/index.htm |archive-url=https://archive.today/20130223214113/http://portal.acs.org/portal/PublicWebSite/education/whatischemistry/landmarks/acrylonitrile/index.htm |url-status=dead |archive-date=23 February 2013 |title=The Sohio Acrylonitrile Process |work=National Historic Chemical Landmarks |publisher=American Chemical Society |access-date=25 June 2012 }}</ref>
<ref>{{cite web
| date = 1 April 2009
| url = http://chemanalytica.com/book/novyy_spravochnik_khimika_i_tekhnologa/06_syre_i_produkty_promyshlennosti_organicheskikh_i_neorganicheskikh_veshchestv_chast_II/5015
| title = 13.1.3.5. Oxidative ammonolysis of hydrocarbons
| publisher = ChemAnalitica.com
| access-date = 22 October 2009
}}</ref>

:{{chem2|(CH2CH2)O + HCN → HOCH2CH2CN}} {{underset|−{{chem2|H2O}}|→}} {{chem2|CH2\dCH\sCN}}

Addition of hydrocyanic acid to ethylene oxide is carried out in the presence of a catalyst ([[Chemistry:Sodium hydroxide|sodium hydroxide]] and diethylamine), and dehydration of cyanohydrin occurs in the gas phase upon the catalytic action of [[Chemistry:Aluminium oxide|aluminium oxide]].<ref>
{{cite book
| author1 = Andreas, F.
| author2 = Grabe, K.
| title = Propylenchemie
| publisher = Akademie-Verlag
| year = 1969
| pages = 117–118
}}</ref>

==Non-industrial uses==

The direct use of ethylene oxide accounts for only 0.05% (2004 data) of its global production.<ref name="iars" /> Ethylene oxide is used as a sterilizing agent, disinfecting agent and [[Biology:Fumigation|fumigant]] as a mixture with carbon dioxide (8.5–80% of ethylene oxide), nitrogen or [[Chemistry:Dichlorodifluoromethane|dichlorodifluoromethane]] (12% ethylene oxide). It is applied for gas-phase sterilization of medical equipment and instruments, packaging materials and clothing, surgical and scientific equipment;<ref name="iars">{{cite book
 |chapter      = Vol. 97. 1,3-Butadiene, Ethylene Oxide and Vinyl Halides (Vinyl Fluoride, Vinyl Chloride and Vinyl Bromide)
 |title        = IARC Monographs on the Evaluation of Carcinogenic Risks to Humans
 |location     = Lyon
 |publisher    = International Agency for Research on Cancer
 |year         = 2008
 |chapter-url          = http://monographs.iarc.fr/ENG/Monographs/vol97/
 |pages        = 185–287
 |isbn         = 978-92-832-1297-3
 |access-date  = 11 January 2019
|archive-url  = https://web.archive.org/web/20161225052600/http://monographs.iarc.fr/ENG/Monographs/vol97/
 |archive-date = 25 December 2016
|url-status     = dead
 |df           = dmy-all
}}</ref> for processing of storage facilities (tobacco, packages of grain, sacks of rice, etc.), clothing, furs and valuable documents.<ref name="ew">{{cite web |url=http://www.environmentwriter.org/resources/backissues/chemicals/ethylene_oxide.htm |archive-url=https://web.archive.org/web/20060828211843/http://www.environmentwriter.org/resources/backissues/chemicals/ethylene_oxide.htm |url-status=dead |archive-date=28 August 2006 |title=Ethylene oxide |work=Chemical Backgrounders Index |publisher=The Environment Writer |access-date=29 September 2009  }}</ref>

===Healthcare sterilant===
Ethylene oxide is one of the most commonly used sterilization methods in the healthcare industry because of its non-damaging effects for delicate instruments and devices that require sterilization, and for its wide range of material compatibility.<ref>{{cite web
| url = http://www.isomedix.com/services/eo-sterilization/
| title = Ethylene Oxide Sterilization
| publisher = Isometrix
| url-status = bot: unknown
| archive-url = https://web.archive.org/web/20160402020015/http://www.isomedix.com/services/eo-sterilization/
| archive-date = 2 April 2016
| df = dmy-all
}}</ref> It is used for instruments that cannot tolerate heat, moisture or abrasive chemicals, such as electronics, optical equipment, paper, rubber and plastics.<ref>{{cite web
| url = http://multimedia.3m.com/mws/mediawebserver?mwsId=SSSSSu7zK1fslxtUO8_x4x_Gev7qe17zHvTSevTSeSSSSSS--
| title = 3M on EtO sterilizers and EtO sterilization process.
| access-date = 21 March 2013
}}</ref> It was developed in the 1940s as a sterilant by the US military, and its use as a medical sterilant dates to the late 1950s, when the McDonald process was patented for medical devices.<ref>{{cite web
| url = http://www.isomedix.com/services/eo-sterilization/history-of-ethylene-oxide/
| title = History of Ethylene Oxide
| publisher = Isometrix
| url-status = bot: unknown
| archive-url = https://web.archive.org/web/20160402022440/http://www.isomedix.com/services/eo-sterilization/history-of-ethylene-oxide/
| archive-date = 2 April 2016
| df = dmy-all
}}</ref> The [[Chemistry:Anprolene|Anprolene]] system was patented in the 1960s<ref>{{cite web
 |url          = http://www.ovguide.com/harold-willids-andersen-9202a8c04000641f800000000f160f69#
 |title        = Dr. H.W. Andersen's patent of Ethylene Oxide flexible chamber system.
 |access-date   = 21 March 2013
|archive-url  = https://web.archive.org/web/20160306193908/http://www.ovguide.com/harold-willids-andersen-9202a8c04000641f800000000f160f69
 |archive-date = 6 March 2016
|url-status     = dead
 |df           = dmy-all
}}</ref> by Andersen Products,<ref>{{cite web
| url = http://anpro.com/index.htm
| title = Andersen Products
| access-date = 21 March 2013
| archive-date = 26 February 2013
| archive-url = https://web.archive.org/web/20130226140948/http://anpro.com/index.htm
| url-status = dead
}}</ref> and it remains the most commonly used system in several niche markets, notably the veterinary market and some international markets.<ref>{{cite web|url=http://cal.vet.upenn.edu/projects/surgery/2220.htm |title=University of Pennsylvania, EtO uses in veterinarian practices. |access-date=21 March 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131109225657/http://cal.vet.upenn.edu/projects/surgery/2220.htm |archive-date=9 November 2013 }}</ref> It relies on the use of a flexible sterilization chamber and an EtO cartridge for small volume sterilization, and where environmental and/or portability considerations dictate the use of a low dose. It is therefore referred to as the "flexible chamber sterilization" method, or the "gas diffusion sterilization" method.

In the United States, the operation of EtO sterilization is overseen by the EPA through the [[Chemistry:National Emissions Standards for Hazardous Air Pollutants|National Emissions Standards for Hazardous Air Pollutants]] (NESHAP).<ref>
{{Cite web
| last = US EPA
| first = OAR
| title = Ethylene Oxide Emissions Standards for Sterilization Facilities: National Emission Standards for Hazardous Air Pollutants (NESHAP)
| format = Other Policies and Guidance
| accessdate = 30 December 2021
| date = 25 June 2015
| url = https://www.epa.gov/stationary-sources-air-pollution/ethylene-oxide-emissions-standards-sterilization-facilities
}}
</ref>

===Niche uses===
Ethylene oxide is used as a [[Biology:Fungicide|fungicide]] and as an accelerator of maturation of tobacco leaves.<ref name="ew" /> Ethylene oxide is also used as a main component of thermobaric weapons (fuel-air explosives).<ref name=e1>{{cite book|url=https://books.google.com/books?id=ZzlNgS70OHAC&pg=PA136|page=136|title=Weapons of mass destruction: an encyclopedia of worldwide policy, technology, and history, Volume 2|author1=Croddy, Eric  |author2=Wirtz, James J. |isbn=1-85109-490-3|publisher=ABC-CLIO|year=2005}}</ref><ref name=e2>{{cite book|url=https://archive.org/details/Explosives._6th_Edition|page=[https://archive.org/details/Explosives._6th_Edition/page/n154 142]|title=Explosives|author1=Meyer, Rudolf |author2=Köhler, Josef |author3=Homburg, Axel |publisher=Wiley-VCH|year=2007|isbn=978-3-527-31656-4}}</ref><ref>Hardy, Periam B.; Gay, Lewis L. and Husler, Edward L. (2 January 1979) "Fuel-air type bomb" {{US Patent|4132170}}</ref>

==Identification of ethylene oxide==
[[Gas chromatography]] is the principal method for analysis and detection of ethylene oxide.<ref name="iars" />

An inexpensive test for ethylene oxide exploits its precipitation of solid hydroxides of metals when it is passed through aqueous solutions of their salts:

:<chem>2 (CH2CH2)O + MnCl2 + 2 H2O -> 2 HO-CH2CH2-Cl + Mn(OH)2 v</chem>

Similarly, ethylene oxide is detected by the bright pink color of the indicator when passing air through aqueous solutions of some salts of sodium or potassium (chlorides, iodides, thiosulfates, etc.) with the addition of [[Chemistry:Phenolphthalein|phenolphthalein]]:<ref name="oe4">{{cite book
| chapter = Chapter IV Methods of analysis of ethylene oxide
| title = Ethylene oxide
| editor1=Zimakov, P.V.
| editor2=Dyment, O. H.
| publisher = Khimiya
| year = 1967
| pages = 128–140
}}</ref>

:<chem>(CH2CH2)O + NaCl + H2O -> HO-CH2CH2-Cl + NaOH</chem>

Other methods of ethylene oxide detection are<ref name="oe4" /> color reactions with [[Chemistry:Pyridine|pyridine]] derivatives and hydrolysis of ethylene glycol with [[Chemistry:Periodic acid|periodic acid]]. The produced [[Chemistry:Iodic acid|iodic acid]] is detected with [[Chemistry:Silver nitrate|silver nitrate]].

{{anchor|Fire and explosion hazards}}

==Accidents==
Ethylene oxide is extremely flammable, and its mixtures with air are explosive. When heated it may rapidly expand, causing fire and explosion.<ref>{{cite web|url=http://www.safework.ru/ilo/ICSC/cards/view/?0155 |title=Ethylene oxide |work=ICSC/International Chemical Safety Cards |publisher=Institute of Industrial Safety, Labour Protection and Social Partnership |access-date=21 September 2009 |url-status=dead |archive-url=https://web.archive.org/web/20051228201427/http://www.safework.ru/ilo/ICSC/cards/view/?0155 |archive-date=28 December 2005 }}</ref> Several industrial accidents have been attributed to ethylene oxide explosion.<ref>{{cite web|url=http://www.csb.gov/csb-issues-final-report-in-2004-explosion-at-sterigenics-international-facility-in-ontario-california-notes-lack-of-engineering-controls-understanding-of-process-hazards/|title=CSB Issues Final Report in 2004 Explosion at Sterigenics International Facility in Ontario, California: Notes Lack of Engineering Controls, Understanding of Process Hazards – Investigations – News – CSB |website=www.csb.gov |access-date=29 March 2018}}</ref><ref>{{cite web|url=http://www.csb.gov/videos/ethylene-oxide-explosion-at-sterigenics/|title=Ethylene Oxide Explosion at Sterigenics – Safety Videos – Multimedia – CSB |website=www.csb.gov |access-date=29 March 2018}}</ref><ref>{{cite web|url=https://www.osha.gov/pls/imis/establishment.inspection_detail?id=105522072|title=OSHA Inspection Detail |website=www.osha.gov |access-date=24 May 2018}}</ref>

The [[Chemistry:Autoignition temperature|autoignition temperature]] is {{Convert|429|C|}}, [[Physics:Thermal decomposition|decomposition temperature]] of {{Convert|571|C|}} at {{Convert|101.3|kPa||abbr=on}}, minimum inflammable content in the air is 2.7%,<ref>{{cite web
| year = 1988
| url = http://www.inchem.org/documents/hsg/hsg/hsg016.htm
| title = Ethylene Oxide
| work = Health and Safety Guide
| publisher = International Programme on Chemical Safety (IPCS) INCHEM
| access-date = 23 September 2009
}}</ref> and maximum limit is 100%. The NFPA 704 rating is Health, 3; Flammability, 4; Instability 2.<ref>{{Cite web |title=ETHYLENE OXIDE WITH NITROGEN {{!}} CAMEO Chemicals {{!}} NOAA |url=https://cameochemicals.noaa.gov/chemical/19324 |access-date=2023-03-21 |website=cameochemicals.noaa.gov}}</ref> Ethylene oxide in presence of water can hydrolyze to ethylene glycol and form polyethylene oxide, which then eventually is oxidized by air and leads to [[Physics:Hot spot effect in subatomic physics|hotspots]] that can trigger explosive decomposition.

Fires caused by ethylene oxide are extinguished with conventional media including foam, carbon dioxide or water. Suppression of this activity can be done by blanketing with an [[Physics:Inert gas|inert gas]] until total pressure reaches the nonexplosive range. Extinguishing of burning ethylene oxide is complicated by its ability to continue burning in an inert atmosphere and in water solutions. Fire suppression is reached only upon dilution with water above 22:1.<ref>{{cite web
 |url        = http://s01.static-shell.com/content/dam/shell/static/chemicals/downloads/products-services/ethylene-oxide-safetyliteraturevi.pdf
 |archive-url = https://web.archive.org/web/20160303235017/http://s01.static-shell.com/content/dam/shell/static/chemicals/downloads/products-services/ethylene-oxide-safetyliteraturevi.pdf
 |url-status   = dead
 |archive-date = 3 March 2016
|title      = Ethylene Oxide Safety Literature
 |publisher  = Shell Chemicals
 |access-date = 23 October 2009
}}</ref>

===La Canonja, Spain accident===
On 14 January 2020 in an industrial estate near Tarragona, an explosion of an ethoxylation reactor owned by the chemical company Industrias Quimicas de Oxido de Etileno (IQOXE, part of the CL Industrial Group) occurred.<ref>{{Cite web|url=https://www.icis.com/explore/resources/news/2020/01/15/10459345/tarragona-chemicals-park-running-normally-after-iqoxe-blast-leaves-two-dead|title=Tarragona chemicals park running normally after IQOXE blast leaves two dead|last=Lopez|first=Jonathan|website=Icis|access-date=16 January 2020}}</ref><ref>Galocha, A.; Zafra, M. and Clemente, Y. (16 January 2020) [https://elpais.com/politica/2020/01/15/actualidad/1579111718_307276.html Reconstrucción visual | Así fue la explosión en la petroquímica de Tarragona]. ''El País''</ref> The accident launched substantial debris over a radius of about two and a half kilometers, one piece penetrating a distant home and killing an occupant.<ref>[https://www.bbc.com/news/world-europe-51113132 Spanish chemical plant explosion kills man 3km away]. ''BBC''. 15 January 2020</ref> It is  reported that at least three people were killed and seven  injured as a direct result of the explosion.<ref>[https://www.elmundo.es/cataluna/2020/01/15/5e1eceedfdddffd9948b45de.html Muere una tercera persona a causa de la explosión en la planta petroquímica de Tarragona]. ''El Mundo''. 15 January 2020</ref>

The company was, until the time of the explosion the only producer of ethylene oxide in Spain with an installed capacity of 140,000 tons/year. Half of that production was used to manufacture ethylene glycol for PET production.<ref>[https://web.archive.org/web/20160531094348/https://www.iqoxe.com/en/the-company/who-we-are Who we are]. IQOXE Company</ref> The accident will be investigated under EU regulations within the context of the European Agency for Safety and Health at Work.

=== 2020 sesame seeds contamination ===
In September 2020, high levels of pesticides were found in 268 tonnes of [[Biology:Sesame|sesame]] seeds from {{wipe|India}}. The contamination had a level of 1000 to 3500 times the limit of 0.05 milligrams per kilogram for ethylene oxide allowed in [[Earth:Europe|Europe]]. This pesticide is forbidden in Europe, it is known to be carcinogenic and mutagenic. A product recall was made, half of the products had an organic certification.<ref>{{Cite web|title=EU toughens rules for sesame seeds from India|date=30 September 2020|url=https://www.foodsafetynews.com/2020/09/multi-country-recalls-due-to-ethylene-oxide-in-sesame-seeds/|author=Clark, Marler |work=Food Safety News}}</ref><ref>{{Cite web|title=franceinfo conso. A carcinogenic pesticide in sesame seeds|url=https://pledgetimes.com/franceinfo-conso-a-carcinogenic-pesticide-in-sesame-seeds-2/|work=Pledge Times|author=Mandalia, Bhavi  |date=21 November 2020|archive-url=https://web.archive.org/web/20201201133316/https://pledgetimes.com/franceinfo-conso-a-carcinogenic-pesticide-in-sesame-seeds-2/|archive-date=1 December 2020}}</ref>

In September, alert was raised by Belgium by RASFF, but the product has also been sold in other EU single market countries such as France<ref>[https://www.economie.gouv.fr/dgccrf/avis-de-rappel-de-produits-contenant-du-sesame Sésame, psyllium, épices et autres produits rappelés comprenant ces ingrédients]. economie.gouv.fr</ref> and Ireland.

== Physiological effects ==

===Effect on microorganisms===
Exposure to ethylene oxide gas causes [[Chemistry:Alkylation|alkylation]] to microorganisms at a nuclear level.<ref>{{cite web|url=http://naspco.com/sterilization/|title=Ethylene Oxide Sterilization|website=NASPCO|access-date=10 February 2017|archive-url=https://web.archive.org/web/20180708031254/http://naspco.com/sterilization/|archive-date=8 July 2018|url-status=dead}}</ref> The disinfectant effect of ethylene oxide is similar to that of sterilization by heat, but because of limited penetration, it affects only the surface. ETO sterilization can take up to 12 hours due to its slow action upon microorganisms, and lengthy processing and aeration time.<ref>{{cite web|url=https://microbeonline.com/ethylene-oxide-eto-properties-mode-action-uses/author=Tankeshwar,|title=Ethylene Oxide (ETO): Properties, Mode of Action and Uses|date=26 December 2013|website=Microbe Online|access-date=10 February 2017}}{{Dead link|date=March 2022 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

===Effects on humans and animals===
Ethylene oxide is an [[Chemistry:Alkylation|alkylating agent]]; it has irritating, sensitizing and narcotic effects.<ref name="ChemAnalitica11">{{cite web
| date = 1 April 2009
| url = http://chemanalytica.com/book/novyy_spravochnik_khimika_i_tekhnologa/11_radioaktivnye_veshchestva_vrednye_veshchestva_gigienicheskie_normativy/5177
| title = Harmful substances. Section 4. Heterocyclic compounds. Triplex heterocyclic compounds
| publisher = ChemAnalitica.com
| access-date = 21 September 2009
}}</ref> Chronic exposure to ethylene oxide is also [[Physics:Mutagen|mutagen]]ic. The [[Organization:International Agency for Research on Cancer|International Agency for Research on Cancer]] classifies ethylene oxide into group 1, meaning it is a proven [[Biology:Carcinogen|carcinogen]].<ref name = "basesafework" >{{cite encyclopedia
| author = Collins J. L.
| url = http://base.safework.ru/iloenc?hdoc&nd=857300040&nh=0
| title = Epoxy compounds
| encyclopedia = Encyclopedia of the ILO
| publisher = Institute of Industrial Safety, Labour Protection and Social Partnership
| access-date = 25 September 2009}}</ref><ref>{{cite book
 |chapter      = Vol. 60. Some Industrial Chemicals
 |title        = IARC Monographs on the Evaluation of Carcinogenic Risks to Humans
 |location     = Lyon
 |publisher    = International Agency for Research on Cancer
 |year         = 1999
 |chapter-url          = http://monographs.iarc.fr/ENG/Monographs/vol60/
 |isbn         = 978-92-832-1297-3
 |access-date  = 28 June 2007
|archive-url  = https://web.archive.org/web/20160303232338/http://monographs.iarc.fr/ENG/Monographs/vol60/
 |archive-date = 3 March 2016
|url-status     = dead
 |df           = dmy-all
}}</ref> Ethylene oxide is classified as a class 2 carcinogen by the German MAK commission and as a class A2 carcinogen by the ACGIH. A 2003 study of 7,576 women exposed while at work in commercial sterilization facilities in the US suggests ethylene oxide is associated with [[Medicine:Breast cancer|breast cancer]] incidence.<ref>{{Cite journal | doi = 10.1023/A:1024891529592|pmid=12948284| title=Ethylene oxide and breast cancer incidence in a cohort study of 7576 women (United States)| year = 2003| last1 = Steenland | first1 = K. | journal = Cancer Causes and Control| volume = 14| issue = 6| pages = 531–9| last2 = Whelan | first2 = E. | last3 = Deddens | first3 = J. | last4 = Stayner | first4 = L. | last5 = Ward | first5 = E. |s2cid=20888472}}</ref> A 2004 follow up study analyzing 18,235 men and women workers exposed to ethylene oxide from 1987 to 1998 concluded "There was little evidence of any excess cancer mortality for the cohort as a whole, with the exception of bone cancer based on small numbers. Positive exposure-response trends for lymphoid tumors were found for males only. Reasons for the sex specificity of this effect are not known. There was also some evidence of a positive exposure-response for breast cancer mortality."<ref>{{Cite journal
| pmid = 14691266
| pmc = 1757803
| year = 2004
| last1 = Steenland
| first1 = K
| title = Mortality analyses in a cohort of 18 235 ethylene oxide exposed workers: Follow up extended from 1987 to 1998
| journal = Occupational and Environmental Medicine
| volume = 61
| issue = 1
| pages = 2–7
| last2 = Stayner
| first2 = L
| last3 = Deddens
| first3 = J
}}</ref> An increased incidence of brain tumors and mononuclear cell leukemia was found in rats that had inhaled ethylene oxide at concentrations of {{Convert|10|,|33|or|abbr=on|100|mL/m3}} over a period of two years.<ref name=msds2>[https://web.archive.org/web/20120313031850/http://www.atsdr.cdc.gov/toxprofiles/tp137.pdf Toxicological Profile For Ethylene Oxide]. Agency for Toxic Substances and Disease Registry, US Public Health Services</ref> An increased incidence of peritoneal mesotheliomas was also observed in the animals exposed to concentrations of {{Convert|33|and|100|mL/m3|abbr=on|4}}. Results of human epidemiological studies on workers exposed to ethylene oxide differ. There is evidence from both human and animal studies that inhalation exposure to ethylene oxide can result in a wide range of carcinogenic effects.

Ethylene oxide is toxic by inhalation, with a US [[Organization:Occupational Safety and Health Administration|OSHA]] permissible exposure limit calculated as a TWA (time weighted average) over 8 hours of 1{{nbsp}}ppm, and a short term exposure limit (excursion limit) calculated as a TWA over 15 minutes of 5{{nbsp}}ppm.<ref name="msds"/>  At concentrations in the air about 200 parts per million, ethylene oxide irritates [[Biology:Mucous membrane|mucous membrane]]s of the nose and throat; higher contents cause damage to the trachea and bronchi, progressing into the partial collapse of the lungs. High concentrations can cause [[Medicine:Pulmonary edema|pulmonary edema]] and damage the cardiovascular system; the damaging effect of ethylene oxide may occur only after 72 hours after exposure.<ref name="atsdr" /> The maximum content of ethylene oxide in the air according to the US standards ([[Organization:American Conference of Governmental Industrial Hygienists|ACGIH]]) is {{Convert|1.8|mg/m3||abbr=on}}.<ref>{{cite book
|author1=Carson P.A. |author2=Mumford C.J. | title = Hazardous Chemicals Handbooks
| location = Oxford
| publisher = Butterworth-Heinemann Ltd
| year = 1994
| page = 85
| isbn = 0-7506-0278-3
}}</ref> [[Organization:National Institute for Occupational Safety and Health|NIOSH]] has determined that the Immediately Dangerous to Life and Health level (IDLH) is 800 ppm.<ref>[https://www.cdc.gov/niosh/idlh/intridl4.html Immediately Dangerous To Life or Health (IDLH) Values]. Cdc.gov. Retrieved on 8 May 2017.</ref>

Because the odor threshold for ethylene oxide varies between 250 and 700 ppm, the gas is already at toxic concentrations when it can be smelled. Even then, the odor of ethylene oxide is sweet and aromatic and can easily be mistaken for the aroma of [[Chemistry:Diethyl ether|diethyl ether]], a common laboratory solvent of very low toxicity. In view of these insidious properties, continuous electrochemical monitoring is standard practice, and it is forbidden to use ethylene oxide to fumigate building interiors in the [[Social:European Union|EU]] and some other jurisdictions.<ref name=bnpuk>{{cite web
| last = Chemicals Regulation Directorate
| title = Banned and Non-Authorised Pesticides in the United Kingdom
| url = http://www.pesticides.gov.uk/guidance/industries/pesticides/topics/pesticide-approvals/pesticides-registration/Withdrawal-and-Restrictions/banned-and-non-authorised-pesticides| access-date = 1 December 2009
}}</ref>

Ethylene oxide causes acute poisoning, accompanied by a variety of symptoms.<ref name = "ChemAnalitica11" /> Central nervous system effects are frequently associated with human exposure to ethylene oxide in occupational settings. Headache, nausea, and vomiting have been reported.{{clarify|date=February 2017|reason="50 years of reports and/or 50 years of symptoms post-exposure?"}} Peripheral neuropathy, impaired hand-eye coordination and memory loss have been reported in more recent case studies of chronically-exposed workers at estimated average exposure levels as low as 3 ppm (with possible short-term peaks as high as 700{{nbsp}}ppm).<ref name=msds2/> The metabolism of ethylene oxide is not completely known. Data from animal studies indicate two possible pathways for the metabolism of ethylene oxide: hydrolysis to ethylene glycol and glutathione conjugation to form [[Chemistry:Mercapturic acid|mercapturic acid]] and meththio-metabolites.

Ethylene oxide easily penetrates through ordinary clothing and footwear, causing skin irritation and dermatitis with the formation of blisters, fever and [[Medicine:Leukocytosis|leukocytosis]].<ref name="ChemAnalitica11" />

Toxicity data for ethylene oxide are as follows:<ref name="msds">{{cite book|author=Simmons, H. Leslie|title=Building Materials: Dangerous Properties of Products in MasterFormat Divisions 7 and 9|url=https://books.google.com/books?id=MH9DrW0UGvwC&pg=PA146|year=1997|publisher=John Wiley & Sons|isbn=978-0-442-02289-1|page=146}} [http://chemistry.umeche.maine.edu/Safety/ReadMSDS.html Codes] {{Webarchive|url=https://web.archive.org/web/20150402124719/http://chemistry.umeche.maine.edu/Safety/ReadMSDS.html |date=2 April 2015 }}.</ref>
* Eye exposure: {{Convert|18|mg||abbr=on}}/6 hours (rabbit)
* Oral: {{Convert|72|mg/kg||abbr=on}} (rat, [[Chemistry:Median lethal dose|LD<sub>50</sub>]]), {{Convert|1186|mg/kg||abbr=on}} (rat, [[Chemistry:Lowest published toxic dose|TD<sub>Lo</sub>]]), {{Convert|5112|mg/kg||abbr=on}} (rat, TD)
* Inhalation: 12,500 ppm (human, [[Chemistry:Median lethal dose#Other measures of toxicity|TC<sub>Lo</sub>]]), 960 ppm/4 hours (dog, [[Chemistry:Median lethal dose|LC<sub>50</sub>]]) 33–50 ppm (rat or mouse, TC), 800 ppm/4 hours (rat or mouse, LC<sub>50</sub>)
* [[Medicine:Subcutaneous injection|Subcutaneous injection]]: {{Convert|100|mg/kg||abbr=on}} (cat, LD<sub>Lo</sub>), {{Convert|292|mg/kg||abbr=on}} (mouse, TD<sub>Lo</sub>) {{Convert|900-2600|mg/kg||abbr=on}} (mouse, TD), {{Convert|187|mg/kg||abbr=on}} (rat, LD<sub>50</sub>).
* [[Medicine:Intraperitoneal injection|Intraperitoneal injection]]: {{Convert|750|mg/kg||abbr=on}} (mouse, TD<sub>Lo</sub>), {{Convert|175|mg/kg||abbr=on}} (mouse, LD<sub>50</sub>)
* Intravenous injection: {{Convert|175|mg/kg||abbr=on}} (rabbit, LD<sub>50</sub>), {{Convert|290|mg/kg||abbr=on}} (mouse, LD<sub>50</sub>)
* The US Environmental Protection Agency (USEPA) estimated in 2016<ref>{{Cite book|title=Evaluation of the Inhalation Carcinogenicity of Ethylene Oxide|publisher=US Environmental Protection Agency|year=2016|url=https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/1025tr.pdf}}</ref> that for low doses, the inhalation of ethylene oxide for a lifetime could increase an individual's lifetime cancer risk by as much as 3.0{{nbsp}}×{{nbsp}}10<sup>−3</sup> per μg/m<sup>3</sup> (without considering that early-life exposures are likely more potent).  The USEPA estimated the slope of the dose-response declines at higher doses, and extra cancer risk estimates for several occupational exposure scenarios are calculated.

== Global demand ==
Global EO demand has expanded from {{Convert|16.6|Mt|e6ST|lk=in|abbr=unit}} in 2004 to {{Convert|20|Mt|e6ST|abbr=unit}} in 2009, while demand for refined EO expanded from {{Convert|4.64|Mt|e6ST|abbr=unit}} in 2004 to {{Convert|5.6|Mt|e6ST|abbr=unit}} in 2008. In 2009, demand is estimated to have declined to about {{Convert|5.2|Mt|e6ST|abbr=unit}}. Total EO demand registered a growth rate of 5.6% per annum during the period 2005 to 2009 and is projected to grow at 5.7% per annum during 2009 to 2013.<ref name = dutia>{{cite journal |last=Dutia |first=Pankaj |title=Ethylene Oxide: A Techno-Commercial Profile |url=http://www.chemicalweekly.com/Profiles/Ethylene_Oxide.pdf |journal=Chemical Weekly |date=26 January 2010|url-status = dead|archive-url = https://web.archive.org/web/20150402145434/http://www.chemicalweekly.com/Profiles/Ethylene_Oxide.pdf|archive-date = 2 April 2015}}</ref>

==Health and safety regulations==
According to Merck Life Science UK 2020 Safety Data Sheet provided to the [[Organization:European Chemicals Agency|European Chemicals Agency]]'s [[Chemistry:Registration, Evaluation, Authorisation and Restriction of Chemicals|Registration, Evaluation, Authorisation and Restriction of Chemicals]] (REACH)—a 2006 European Union regulation,<ref>[https://eur-lex.europa.eu/legal-content/en/ALL/?uri=CELEX%3A32006R1907 Regulation (EC) No 1907/2006]. European Parliament. 18 December 2006</ref> ethylene oxide is "presumed to have carcinogenic potential for humans."<ref name="sigmaaldrich 2020"/>

The United States EPA published an advance notice of proposed rulemaking (NPRM) in the 12 December 2019 Federal Register seeking to limit EtO emissions.<ref>{{Cite web |title=ETO Advance NPRM |url=https://www.govinfo.gov/content/pkg/FR-2019-12-12/pdf/2019-26804.pdf}}</ref> Over the next couple of years, information was collected and a proposed air toxics rule published in the 13 April 2023 Federal Register.<ref>{{Cite web |title=Federal Register :: Request Access |url=https://unblock.federalregister.gov/ |access-date=2023-05-26 |website=unblock.federalregister.gov}}</ref> Following a 60 day comment period that could be extended, due to many comments requesting an extension, the EPA rules that could reduce EtO emissions, both direct and fugitive, by over 80% could be implemented within 18 months of publishing the final rule in the Federal Register.<ref>{{Citation |title=U.S. EPA Public Meeting: ETO National Public Webinar |url=https://www.youtube.com/watch?v=eQV59R3jsxQ |access-date=2023-05-26 |language=en}}</ref> Laboratory EtO emitters would still be exempt from the stricter compliance. Additionally, while effectively curbing EtO emissions in the USA, many industrial emitters may simply shift their EtO production to nearby less strict countries: Canada, Mexico, etc.

==References==
{{reflist}}

==Cited sources==
* {{cite book
 | editor-last = Haynes | editor-first = William M.
 | date = 2011
 | title = CRC Handbook of Chemistry and Physics
 | title-link = CRC Handbook of Chemistry and Physics
 | edition = 92nd
 | publisher = CRC Press
 | location = Boca Raton, FL
 | isbn = 978-1439855119|ref=Haynes
}}

==External links==
*[http://www.eosa.org EOSA Promoting the safe use of Ethylene Oxide for Sterilization]
*[http://webbook.nist.gov/cgi/cbook.cgi?ID=C75218 WebBook page for C2H4O]
*[https://www.cdc.gov/niosh/topics/ethyleneoxide/ National Institute for Occupational Safety and Health – Ethylene Oxide Topic Page]
*[https://www.cdc.gov/niosh/npg/npgd0275.html CDC – NIOSH Pocket Guide to Chemical Hazards]
*[http://www.anpro.com/articles/EOSA%20update%20article.htm EOSA memo about Ethylene Oxide (EtO) facts] {{Webarchive|url=https://web.archive.org/web/20171015044858/http://www.anpro.com/articles/EOSA%20update%20article.htm |date=15 October 2017 }}

{{Molecules detected in outer space}}

[[Category:Biocides]]
[[Category:Epoxides]]
[[Category:Fungicides]]
[[Category:Hazardous air pollutants]]
[[Category:IARC Group 1 carcinogens]]
[[Category:Monomers]]
[[Category:Commodity chemicals]]
[[Category:Gaseous signaling molecules]]
[[Category:Explosive chemicals]]

{{Sourceattribution|Ethylene oxide}}