Editing Ethylene oxide (section)

==Chemical properties==
Ethylene oxide readily reacts with diverse compounds with opening of the ring. Its typical reactions are with nucleophiles which proceed via the '''[[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|class=skin-invert-image]]

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. However adding a small amount of acid, such as strongly diluted [[sulfuric acid]], immediately leads to the formation of [[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 [[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 [[diethylene glycol|di-]] and [[triethylene glycol]]:<ref>{{cite web |title=Epoxyethane (Ethylene Oxide) |work=Alkenes menu |publisher=Chemguide |url=https://www.chemguide.co.uk/organicprops/alkenes/epoxyethane.html |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 [[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 [[alcohol (chemistry)|alcohols]] 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 [[sodium]] metal, [[sodium hydroxide]], or [[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 [[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 [[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 |isbn=978-0-8247-9997-7 |url=https://books.google.com/books?id=YoZ6CjYNLoQC&pg=PA129}}</ref> The carboxylate ion acts as [[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 [[ammonia]] forming a mixture of mono-, di-, and tri- [[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

[[Trimethylamine]] reacts with ethylene oxide in the presence of water, forming [[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 [[hydrochloric acid|hydrochloric]], [[hydrobromic acid|hydrobromic]], and [[hydroiodic acid]]s to form [[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 [[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 [[hydrogen fluoride]] with a 5–6% solution of ethylene oxide in [[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 |publisher=W. A. Benjamin |year=1969 |page=98 |isbn=0-8053-8790-0 |url=https://archive.org/details/organicfluorinec0000shep |url-access=registration}}</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 [[Grignard reaction|Grignard reagents]], can be regarded as [[nucleophilic substitution]] influenced by [[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 [[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 [[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 [[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 [[hydrogen sulfide]], ethylene oxide forms [[2-Mercaptoethanol|2-mercaptoethanol]] and [[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 [[barium nitrite]], [[calcium nitrite]], [[magnesium nitrite]], [[zinc nitrite]], or [[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 [[nitric acid]], ethylene oxide forms mono- and [[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 [[alkoxide]]s, reactions of ethylene oxide with compounds containing active methylene group leads to the formation of [[gamma-Butyrolactone|butyrolactones]]:<ref>{{cite book |author=Vogel, A. I. |title=Vogel's Textbook of practical organic chemistry |edition=5 |location=UK |publisher=Longman Scientific & Technical |year=1989 |page=1088 |isbn=0-582-46236-3 |url=https://archive.org/details/Vogels_Textbook_of_Practical_Organic_Chemistry_5ed_1989_Longman_WW}}</ref>
: [[File:2-ACETYLBUTYROLACTONE-SYNTHESIS.png|550px|Synthesis of 2-acetylbutyrolactone|class=skin-invert-image]]

====Alkylation of aromatic compounds====
Ethylene oxide enters into the [[Friedel–Crafts reaction]] with benzene to form [[phenethyl alcohol]]:
: [[File:Oxirane+benzene.png|400px|class=skin-invert-image|Friedel-Crafts reaction with ethylene oxide]]

[[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 [[heterocyclic compound]]s, known as [[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. Their Characteristics 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 [[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 |volume=24|issue=8  |page=695 |doi=10.1002/anie.198506951}}</ref>
: [[File:Tetraoxathia-2-cycloundecanone.png|350px|class=skin-invert-image]]

===Isomerization===
When heated to about {{convert|400|C||sigfig=2}}, or to {{convert|150–300|C||sigfig=2}} in the presence of a catalyst ([[aluminium oxide|Al<sub>2</sub>O<sub>3</sub>]], [[phosphoric acid|H<sub>3</sub>PO<sub>4</sub>]], etc.), ethylene oxide [[isomerization|isomerizes]] into [[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
|journal=The Journal of Chemical Physics
|year=1964
|volume=40 |issue=1
|page=105
|bibcode=1964JChPh..40..105B
|doi=10.1063/1.1729851}}</ref>

{{Numbered block|: |(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}}}}

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

{{Numbered block|: |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 [[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|Thermal decomposition]]).<ref name="oe2"/>

===Reduction reaction===
Ethylene oxide can be hydrogenated into ethanol in the presence of a catalyst, such as [[nickel]], [[platinum]], [[palladium]],<ref name="oe2"/> [[borane]]s, [[lithium aluminium hydride]], and some other [[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 [[acetic acid]], of lithium aluminium hydride with [[titanium trichloride]] (the reducing agent is actually [[titanium(II) chloride|titanium dichloride]], formed by the reaction between LiAlH<sub>4</sub> and TiCl<sub>3</sub>) and of [[iron(III) chloride]] with [[butyllithium]] in [[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 [[glycolic acid]] or [[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>, [[carbon monoxide|CO]], [[carbon dioxide|CO<sub>2</sub>]], [[methane|CH<sub>4</sub>]], [[acetylene|C<sub>2</sub>H<sub>2</sub>]], [[ethylene|C<sub>2</sub>H<sub>4</sub>]], [[ethane|C<sub>2</sub>H<sub>6</sub>]], [[propylene|C<sub>3</sub>H<sub>6</sub>]], [[propane|C<sub>3</sub>H<sub>8</sub>]], and [[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
|bibcode=1996CoFl..106...62D }}</ref>

===Dimerization===
In the presence of acid catalysts, ethylene oxide dimerizes to afford [[dioxane]]:
: [[File:Dioxane-synthesis.png|250px|Synthesis of dioxane|class=skin-invert-image]]

The reaction mechanism is as follows:<ref name="oe2"/>
: [[File:Dioxan-HerstellungCZ.png|650px|Mechanism of dimerization|class=skin-invert-image]]

The dimerization reaction is unselective. By-products include [[acetaldehyde]] (due to [[#Isomerization|isomerization]]). The selectivity and speed of dimerization can be increased by adding a catalyst, such as platinum, platinum-palladium, or [[iodine]] with [[sulfolane]]. 2-methyl-1,3-[[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 [[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> [[Cationic polymerization]] of ethylene oxide is assisted by [[protic]] acids ([[perchloric acid|HClO<sub>4</sub>]], [[hydrochloric acid|HCl]]), Lewis acids ([[Tin(IV) chloride|SnCl<sub>4</sub>]], [[boron trifluoride|BF<sub>3</sub>]], etc.), [[organometallic compound]]s, 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 [[alkoxide]]s, [[hydroxide]]s, [[carbonate]]s, or other compounds of alkali or [[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|isomerization]], however high temperature accelerates the radical processes. They result in a gas mixture containing acetaldehyde, ethane, ethyl, methane, hydrogen, carbon dioxide, [[ketene]], and [[formaldehyde]].<ref>{{cite journal
|author1=Neufeld L.M. |author2=Blades A.T.
|title=The Kinetics of the Thermal Reactions of Ethylene Oxide
|journal=Canadian Journal of Chemistry
|year=1963
|volume=41 |issue=12
|pages=2956–2961
|doi=10.1139/v63-434
|bibcode=1963CaJCh..41.2956N
}}</ref> High-temperature [[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 [[acetylene]] and [[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
|volume=87 |issue=10
|pages=1782–1787
|doi=10.1021/j100233a026
}}</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 [[ethyl group|ethyl]] as the main product, that is to reverse the ethylene oxide synthesis reaction.

===Other reactions===
[[Thiocyanate]] ions or [[thiourea]] transform ethylene oxide into [[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|class=skin-invert-image|mechanism synthesis thiiranes of ethylene oxide under the influence of thiocyanate ion]]

Reaction of [[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 [[sulfuryl chloride]] (SOCl<sub>2</sub>) and [[pyridine]] and of [[triphenylphosphine]] and [[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
|isbn=978-0-471-72091-1
|url=https://books.google.com/books?id=JDR-nZpojeEC
}}</ref>

[[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 [[acyl chloride]]s in the presence of [[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 [[carbon dioxide]], in a non-polar solvent in the presence of ''bis''-(triphenylphosphine)-nickel(0) results in [[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=https://archive.org/details/reagentsfororgan07fies_0/page/545
|url-access=registration
}}</ref>
: [[File:Ethylene-carbonate-syn.png|380px|Synthesis of ethylene carbonate|class=skin-invert-image]]

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
|page=193
|publisher=Springer
|year=1983
|isbn=90-277-1489-4
|url=https://books.google.com/books?id=s1_rjRUlu1EC&pg=PA193}}</ref>

Reaction of ethylene oxide with [[formaldehyde]] at 80–150&nbsp;°C in the presence of a catalyst leads to the formation of [[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|class=skin-invert-image]]

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 [[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>