Ethylene oxide
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2008-06-20T11:58:10Z
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| ImageFileL1 = Ethylene-oxide-2D-skeletal.png
| ImageSizeL1 = 100 px
| ImageFileR1 = Ethylene-oxide-from-xtal-3D-balls.png
| ImageSizeR1 = 150 px
| IUPACName = epoxyethane
| SystematicName =
| OtherNames = ethylene oxide, dimethylene oxide, oxirane, oxacyclopropane
| Section1 = {{Chembox Identifiers
| Abbreviations = EO
| CASNo = 75-21-8
| EINECS = 200-849-9
| EINECSCASNO =
| PubChem = 6354
| SMILES = C1CO1
| InChI = 1/C2H4O/c1-2-3-1/h1-2H2
| RTECS = KX2450000
| MeSHName = Ethylene+Oxide
| ChEBI = 27561
| KEGG = C06548
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| Section2 = {{Chembox Properties
| Formula = C<sub>2</sub>H<sub>4</sub>O
| MolarMass = 44.05 g mol<sup>−1</sup>
| Appearance = colorless gas
| Density = 0.882 g/mL, 7.360 lbs/gallon
| MeltingPt = −111.3 °C
| Melting_notes =
| BoilingPt = 10.7 °C
| Boiling_notes =
| Solubility = miscible
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| Section3 = {{Chembox Structure
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| Section4 = {{Chembox Thermochemistry
| DeltaHf = −52.6 kJ mol<sup>−1</sup>
| DeltaHc =
| Entropy = 243 J mol<sup>−1</sup> K<sup>−1</sup>
| HeatCapacity = }}
| Section5 = {{Chembox Pharmacology
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| Section6 = {{Chembox Explosive
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| Section7 = {{Chembox Hazards
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| NFPA-H = 3
| NFPA-F = 4
| NFPA-R = 3
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| FlashPt = −20 °C
| Autoignition =
| ExploLimits = 3 to 100%
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| Section8 = {{Chembox Related
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The [[chemical compound]] '''ethylene oxide''' is an important industrial chemical used as an intermediate in the production of [[ethylene glycol]] and other chemicals, and as a sterilant for foods and medical supplies. It is a colorless flammable gas or refrigerated liquid with a faintly sweet odor. It is the simplest example of an [[epoxide]].
Its [[IUPAC]] name is '''epoxyethane'''. Other names for it include '''oxirane''' and '''dimethylene oxide'''.
== History ==
Ethylene oxide was first prepared in [[1859]] by the [[France|French]] chemist [[Charles-Adolphe Wurtz]],<ref>{{cite journal|author=Wurtz, A.|journal= Compt. rend.|volume= 48|pages= 101–104 |year=1859| title=}}</ref> who prepared it by treating [[2-Chloroethanol|2-chloroethanol]] with a [[Base (chemistry)|base]]. It achieved industrial importance during [[World War I]] as a precursor to both the coolant [[ethylene glycol]] and the [[chemical weapon]] [[mustard gas]]. In [[1931]], [[Theodore Lefort]], another French chemist, discovered a means to prepare ethylene oxide directly from [[ethylene]] and [[oxygen]], using [[silver]] as a [[catalyst]]. Since [[1940]], almost all ethylene oxide produced industrially has been made using this method.<ref>{{cite journal|title= Manufacture and Uses of Ethylene Oxide and Ethylene Glycol| author= P. P. McClellan| journal= Ind. Eng. Chem.|year= 1950| volume= 42|pages= 2402–2407| doi= 10.1021/ie50492a013}}</ref>
== Production ==
Industrially, ethylene oxide is produced when [[ethylene]] (H<sub>2</sub>C=CH<sub>2</sub>) and [[oxygen]] (O<sub>2</sub>) react on a silver catalyst at 200–300 °C showing large Ag nanoparticles supported on [[alumina]]. Typically, chemical modifiers such as chlorine are also included. Pressures used are in the region of 1-2MPa. The [[chemical equation]] for this [[chemical reaction|reaction]] is:
:H<sub>2</sub>C=CH<sub>2</sub> + ½ O<sub>2</sub> → C<sub>2</sub>H<sub>4</sub>O
The typical yield for this reaction under industrial conditions is 70-80%. In the reaction scheme above, an intermediate (oxametallacycle) is formed. Two different reaction pathways can then occur.
Ethylene oxide formation:
:H<sub>2</sub>C=CH<sub>2</sub> + O → C<sub>2</sub>H<sub>4</sub>O
Acetaldehyde formation:
:H<sub>2</sub>C=CH<sub>2</sub> + O → CH<sub>3</sub>CHO
The latter pathway is the first step in complete [[combustion]], leading to [[carbon dioxide]] and [[water]]:
:CH<sub>3</sub>CHO +5/2 O<sub>2</sub> → 2CO<sub>2</sub> + 2H<sub>2</sub>O
Ethylene oxide can be conveniently produced in the laboratory by the action of an alkali hydroxide on [[ethylene chlorohydrin]].<ref name="s_and_h">{{cite book|title=Introduction to Organic Chemistry|author=Streitwiser, Andrew; Heathcock, Clayton H.|publisher=Macmillan|date=1976|isbn=0-02-418010-6}}</ref>
:CH<sub>2</sub>OH−CH<sub>2</sub>Cl + OH<sup>−</sup> → C<sub>2</sub>H<sub>4</sub>O + Cl<sup>−</sup> + H<sub>2</sub>O
with ethylene chlorohydrin being prepared easily by the action of [[hypochlorous acid]] on [[ethylene]].
Several methods to produce ethylene oxide more selectively have been proposed, but none have achieved industrial importance {{Fact|date=February 2007}}, with notable exceptions as on May 22, 2008 Dr. Bob Benchoff President of A Check Exact labs explains "Important steps have been taken in terms of complying with such injunctions as of US Presidential Policy and Kyoto Protocol, toward overcoming pollution and global warming. Kyoto Protocol for instance lacks the higher dynamic guidance structure necessary to properly accomplish not its proposed specifics yet rather its reason for being, such as by the proper governmental oversight committee properly tied to free enterprise experts in the fields, as I have explained to the White House in simplified terms. In this case of ethylene oxide what once was the Kyoto position against liquid ethylene oxide such as due to its high flammability, within modern dynamics is now faced with improved processing inventions such as RAPREX(R) in various forms of controlled heat related properties used by Sterigenics with long chain branch conditioning as for controlled rheology and many other improvements such as of better mechanical properties than historic unmodified versions, even being better than having full recyclability in the historic sense such as by rather utilizing memory effect, so that the products can be used many times prior to their being recycled in that historic sense and for instance can be used to replace oil."
== Uses ==
Ethylene oxide gas kills [[bacterium|bacteria]] (and their [[endospore]]s), [[mold]], and [[fungi]], and can therefore be used to sterilize substances that would be damaged by sterilizing techniques such as [[pasteurization]] that rely on heat. Ethylene oxide sterilization for the preservation of [[spice]]s was patented in [[1938]] by the [[United States|American]] chemist [[Lloyd Hall]], and it is still used in that role. Additionally, ethylene oxide is widely used to sterilize medical supplies such as bandages, [[sutures]], and surgical implements. The overwhelming majority of medical items are sterilized with ethylene oxide. Preferred methods have been the traditional chamber sterilization method, where a chamber is flooded with a mix of ethylene oxide and other gases which are later [[aerated]], and the more recent gas diffusion method developed in 1967 which relies on a bag that wraps the elements to be sterilized and acts a mini-chamber in order to minimize gas consumption and make the process economically feasible for small loads. Other names for this alternative method for small loads are: [[Anprolene]] method, bag sterilization method or micro-dose sterilization method.
Most ethylene oxide, however, is used as an intermediate in the production of other chemicals. The major use of ethylene oxide is in the production of [[ethylene glycol]]. The primary end use for ethylene glycol is in the production of [[polyester]] polymers. Ethylene glycol is more commonly known for its use as an automotive coolant and [[antifreeze]].
Because of its high flammability and wide explosive concentration range in air, ethylene oxide is sometimes used as the fuel component of a [[fuel-air explosive]].
=== Reactions ===
Most reactions are ring openings by [[nucleophiles]].
In industry, epoxyethane is reacted with [[water]] in the presence of a [[sulfuric acid]] catalyst. A tenfold molar excess of water is used to obtain ethylene glycol:
:C<sub>2</sub>H<sub>4</sub>O + H<sub>2</sub>O → HOCH<sub>2</sub>CH<sub>2</sub>OH
Despite the large excess of water, various types of [[polyethylene glycol]] (PEG) or [[polyethylene oxide]] (PEO) are still formed as secondary products. The degree of [[polymerization]] increases as a smaller proportion of water is used:
: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
For example, under the right conditions it can give [[diethylene glycol]] (HOCH<sub>2</sub>CH<sub>2</sub>OCH<sub>2</sub>CH<sub>2</sub>OH), [[triethylene glycol]], etc.
Similarly, reaction with [[ammonia]] can yield [[ethanolamine]], diethanolamine, or triethanolamine.
Ethylene oxide is also important in the manufacture of [[surfactant]]s and other [[detergent]]s, in a process called [[ethoxylation]].
One class of ethylene oxide derivatives that has attracted much scientific attention is the [[crown ether]]s, which are cyclic [[oligomer]]s of ethylene oxide. These compounds have the ability to make [[ionic compound]]s such as [[salt]]s soluble in nonpolar [[solvent]]s which they otherwise could not dissolve in. However, the high cost of these compounds has largely confined their use to the laboratory rather than industrial practice.
== Health effects ==
Ethylene oxide is toxic by inhalation. Symptoms of overexposure include headache and dizziness, progressing with increasing exposure to convulsions, seizure and coma. It is also an irritant to skin and the respiratory tract, and inhaling the vapors may cause the lungs to fill with fluid several hours after exposure.<ref>http://www.anpro.com/support/MSDS.pdf</ref>
Ethylene oxide is usually stored as a pressurized or refrigerated liquid. At room temperature and pressure, it rapidly evaporates, potentially causing frostbite in cases of skin exposure.
Laboratory animals exposed to ethylene oxide for their entire lives have had a higher incidence of [[liver]] [[cancer]]. However, studies on human beings who have worked with ethylene oxide for extended periods and may have experienced low doses during that time have found no increase in cancer risk. Chronic ethylene oxide exposure may increase the risk of [[cataract]]s in humans.
In animals, ethylene-oxide can cause numerous reproductive effects, including [[mutation]]s and a higher rate of [[miscarriage]]s. Its reproductive effects on humans have not been well studied, but it is considered probable that ethylene oxide exposure has similar effects on human reproduction.
Ethylene oxide is classified as carcinogenic to humans by the International Agency for Research on Cancer (IARC).<ref>[http://monographs.iarc.fr/ENG/Monographs/vol60/volume60.pdf IARC Vol 60<!-- Bot generated title -->]</ref>
== See also ==
* [[Acetaldehyde]]
* [[Ethenol]]
==External links==
*[http://www.npi.gov.au/database/substance-info/profiles/42.html National Pollutant Inventory - Ethylene oxide fact sheet]
*[http://www.americanchemistry.com/s_acc/bin.asp?SID=1&DID=4468&CID=172&VID=109&DOC=File.PDF/html/introduction.html Ethylene Oxide User's Guide]
*[http://www.anpro.com/support/MSDS.pdf Ethylene Oxide MSDS (Material Safety Data Sheet).]
*[http://www.cdc.gov/niosh/topics/ethyleneoxide/ National Institute for Occupational Safety and Health - Ethylene Oxide Topic Page]
==References==
<references/>
[[Category:Ethers]]
[[Category:Epoxides]]
[[Category:Monomers]]
[[Category:Hazardous air pollutants]]
[[Category:Occupational safety and health]]
[[de:Ethylenoxid]]
[[el:Αιθυλενοξείδιο]]
[[es:Óxido de etileno]]
[[fr:Oxyde d'éthylène]]
[[ko:산화 에틸렌]]
[[it:Ossido di etilene]]
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[[zh:环氧乙烷]]