Difference between revisions of "Epoxide" - New World Encyclopedia

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[[Image:Ethylene-oxide-3D-balls.png|thumb|200px|A ball-and-stick model of [[ethylene oxide]], the simplest epoxide.]]
 
[[Image:Ethylene-oxide-3D-balls.png|thumb|200px|A ball-and-stick model of [[ethylene oxide]], the simplest epoxide.]]
[[Image:glycidol.png|thumb|right|200px|The chemical structure of the epoxide [[glycidol]], a common chemical intermediate.]]
 
  
An '''epoxide''' is a cyclic [[ether]] with only three ring atoms. The simplest epoxide is [[ethylene oxide]], also known as ''oxirane'', which is regarded as the "parent" compound. Thus epoxides are also called ''oxiranes''. Epoxides are more reactive than ordinary ethers.
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An '''epoxide''' is a cyclic [[ether]] with only three ring atoms. The simplest epoxide is [[ethylene oxide]], also known as ''oxirane,'' which is regarded as the "parent" compound. Thus, members of the class of epoxides are also called ''oxiranes''. Epoxides are more reactive than ordinary ethers.
 
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{{toc}}
A [[polymer]] containing unreacted epoxide units is called a ''polyepoxide'' or an ''[[epoxy]]''. Epoxy resins are used as [[adhesive]]s and structural materials. Polymerization of an epoxide gives a [[polyether]], for example [[ethylene oxide]] polymerizes to give [[polyethylene glycol]], also known as polyethylene oxide.
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A [[polymer]] containing unreacted epoxide units is called a ''polyepoxide'' or an ''[[epoxy]]''. Epoxy resins are used as [[adhesive]]s and structural materials. Polymerization of an epoxide gives a [[polyether]]. For example, polymerization of [[ethylene oxide]] generates [[polyethylene glycol]], also known as polyethylene oxide, which is commercially the most important form of polyether.
 
 
* "Epoxides (oxiranes) are three-membered cyclic ethers that are easily prepared from alkenes by reaction with peracids. Because of the large angle strain in this small ring, epoxides undergo acid and base-catalyzed C–O bond cleavage more easily than do larger ring ethers."
 
  
 
== Nomenclature ==
 
== Nomenclature ==
 
+
Simple epoxides are named from the parent compound oxirane ([[ethylene oxide]]), such as in ''chloromethyloxirane''. When epoxide is considered a [[functional group]] in a larger compound, it is referred to with the '''epoxy''' [[Prefix (linguistics)|prefix]]. An example is the compound ''1,2-epoxycycloheptane,'' which can also be called ''cycloheptene epoxide''.
Simple epoxides are named from the parent compound oxirane ([[ethylene oxide]]), such as in ''chloromethyloxirane''. When epoxide is considered a [[functional group]] in a larger compound, it is referred to with the '''epoxy''' [[Prefix (linguistics)|prefix]]. An example is the compound ''1,2-epoxycycloheptane'', which can also be called ''cycloheptene epoxide''.
 
  
 
A [[polymer]] containing unreacted epoxide units is called a ''polyepoxide'' or an ''[[epoxy]]''.  
 
A [[polymer]] containing unreacted epoxide units is called a ''polyepoxide'' or an ''[[epoxy]]''.  
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===Olefin peroxidation===
 
===Olefin peroxidation===
Olefin peroxidation, also known as the '''Prilezhaev reaction''',<ref>March, Jerry. 1985. ''Advanced Organic Chemistry: Reactions, Mechanisms and Structure.'' 3rd ed. John Wiley & Sons. ISBN 0471854727.</ref><ref>Prileschajew, Nikolaus. 1909. Oxydation ungesättigter Verbindungen mittels organischer Superoxyde. ''Berichte der deutschen chemischen Gesellschaft''. 42(4): 4811–4815. (doi:10.1002/cber.190904204100.)</ref> involves oxidation of an [[alkene]] with a [[peroxide]], usually a [[peroxyacid]] like [[meta-chloroperoxybenzoic acid]] (m-CPBA) or with a [[dioxirane]] such as [[dimethyldioxirane]] (DMDO). An example is the epoxidation of [[styrene]] with [[perbenzoic acid]] to [[styrene oxide]]:<ref>Hibbert, Harold, and Pauline Burt. 1941. [http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1p0494 Styrene Oxide]. ''Org. Synth.'' Coll. Vol. 1: 494. Retrieved September 22, 2008.</ref>
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Olefin peroxidation, also known as the '''Prilezhaev reaction,'''<ref>Jerry March, ''Advanced Organic Chemistry: Reactions, Mechanisms and Structure,'' 3rd edition. (John Wiley & Sons, 1985, ISBN 0471854727).</ref> involves oxidation of an [[alkene]] with a [[peroxide]], usually a [[peroxyacid]] like [[meta-chloroperoxybenzoic acid]] (m-CPBA) or with a [[dioxirane]] such as [[dimethyldioxirane]] (DMDO). An example is the epoxidation of [[styrene]] with [[perbenzoic acid]] to [[styrene oxide]]:<ref>Harold Hibbert and Pauline Burt, [http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1p0494 Styrene Oxide,] ''Org. Synth.'' Coll. Vol. 1: 494. Retrieved September 22, 2008.</ref>
  
 
:[[Image:PrilezhaevReaction.svg|Prilezhaev Reaction.]]
 
:[[Image:PrilezhaevReaction.svg|Prilezhaev Reaction.]]
  
The reaction proceeds via what is commonly known as the '''Butterfly Mechanism'''.<ref>Bartlett. 1950. ''Rec. Chem. Prog''. 11:47.</ref> It is easiest to consider the oxygen as an [[electrophile]] and the alkene as a [[nucleophile]], although they both operate in that capacity, and the reaction is thought to be concerted. (The numbers in the mechanism below are for simplification.)
+
The reaction proceeds via what is commonly known as the '''Butterfly Mechanism'''.<ref>Bartlett, ''Rec. Chem. Prog'' 11:47.</ref> It is easiest to consider the oxygen as an [[electrophile]] and the alkene as a [[nucleophile]], although they both operate in that capacity, and the reaction is thought to be concerted. (The numbers in the mechanism below are for simplification.)
  
 
:[[Image:ButterflyMech.png|Butterfly Mechanism]]
 
:[[Image:ButterflyMech.png|Butterfly Mechanism]]
  
 
Related processes include some catalytic [[enantioselective]] reactions, such as the:
 
Related processes include some catalytic [[enantioselective]] reactions, such as the:
*[[Sharpless epoxidation]]
+
* [[Sharpless epoxidation]]
 
* [[Jacobsen epoxidation]]
 
* [[Jacobsen epoxidation]]
 
* [[Shi epoxidation]]
 
* [[Shi epoxidation]]
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===Intramolecular S<sub>N</sub>2 substitution===
 
===Intramolecular S<sub>N</sub>2 substitution===
  
This method is a variant of the [[Williamson ether synthesis]]. In this case, the [[alkoxide ion]] and the [[halide]] are right next to each other in the same molecule (such compounds are generically called [[halohydrin]]s), which makes this a simple ring closure reaction. For example, with [[2-chloropropanol]]:<ref>Koppenhoefer, B., and V. Schurig. 1993. [http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv8p0434 (R)-Alkyloxiranes of High Enantiomeric Purity from (S)-2-Chloroalkanoic Acids via (S)-2-Chloro-1-Alkanols: (R)-Methyloxirane]. ''Org. Synth.'' Coll. Vol. 8: 434. Retrieved September 22, 2008.</ref>
+
This method is a variant of the [[Williamson ether synthesis]]. In this case, the [[alkoxide ion]] and the [[halide]] are right next to each other in the same molecule (such compounds are generically called [[halohydrin]]s), which makes this a simple ring closure reaction. For example, with [[2-chloropropanol]]:<ref>B. Koppenhoefer and V. Schurig, [http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv8p0434 (R)-Alkyloxiranes of High Enantiomeric Purity from (S)-2-Chloroalkanoic Acids via (S)-2-Chloro-1-Alkanols: (R)-Methyloxirane,] ''Org. Synth.'' Coll. Vol. 8: 434. Retrieved September 22, 2008.</ref>
  
 
[[Image:Methyloxirane_from_2-chloroproprionic_acid.png|400px]]
 
[[Image:Methyloxirane_from_2-chloroproprionic_acid.png|400px]]
  
 
===Johnson-Corey-Chaykovsky reaction===
 
===Johnson-Corey-Chaykovsky reaction===
 
 
In the [[Johnson-Corey-Chaykovsky reaction]], epoxides are generated from [[carbonyl]] groups and [[sulfonium ylide]]s.
 
In the [[Johnson-Corey-Chaykovsky reaction]], epoxides are generated from [[carbonyl]] groups and [[sulfonium ylide]]s.
  
 
== Reactions ==
 
== Reactions ==
 
 
The three-membered ring of epoxide is approximately an [[equilateral triangle]], that is, its bond angles are about 60°, which makes it highly [[ring strain|strained]]. The strained ring makes epoxides more reactive than other ethers, especially towards [[nucleophile]]s. Typical epoxide reactions are noted below.
 
The three-membered ring of epoxide is approximately an [[equilateral triangle]], that is, its bond angles are about 60°, which makes it highly [[ring strain|strained]]. The strained ring makes epoxides more reactive than other ethers, especially towards [[nucleophile]]s. Typical epoxide reactions are noted below.
  
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:[[Image:EpoxOpen.png]]
 
:[[Image:EpoxOpen.png]]
  
:* Under acidic conditions, the nucleophile attacks the carbon that will form the most stable [[carbocation]], i.e. the ''most substituted'' carbon (similar to a [[halonium]] ion). Under basic conditions, the nucleophile attacks the ''least substituted'' carbon, in accordance with standard S<sub>N</sub>2 nuclephilic addition reaction process.
+
:* Under acidic conditions, the nucleophile attacks the carbon that will form the most stable [[carbocation]], that is, the ''most substituted'' carbon (similar to a [[halonium]] ion). Under basic conditions, the nucleophile attacks the ''least substituted'' carbon, in accordance with standard S<sub>N</sub>2 nuclephilic addition reaction process.
  
* [[Hydrolysis]] of an epoxide in presence of an  [[acid catalyst]] generates a [[glycol]]. The [[hydrolysis]] process of epoxides can be considered to be the [[nucleophilic addition]] of water to the epoxide under [[acid catalysis|acidic]] conditions.
+
* [[Hydrolysis]] of an epoxide in presence of an  [[acid catalyst]] generates a [[glycol]]. The hydrolysis process of epoxides can be considered to be the [[nucleophilic addition]] of water to the epoxide under [[acid catalysis|acidic]] conditions.
  
 
* [[organic reduction|Reduction]] of an epoxide  with [[lithium aluminum hydride]] and [[water]] generates an [[alcohol]]. This reduction process can be considered to be the nucleophilic addition of hydride (H-) to the epoxide under basic conditions.
 
* [[organic reduction|Reduction]] of an epoxide  with [[lithium aluminum hydride]] and [[water]] generates an [[alcohol]]. This reduction process can be considered to be the nucleophilic addition of hydride (H-) to the epoxide under basic conditions.
  
* Reduction with [[tungsten hexachloride]] and [[N-Butyllithium|''n''-butyllithium]] generates the [[alkene]]. This reaction in effect is a '''de-epoxidation''':<ref>Sharpless, K. Barry, Martha A. Umbreit, Marjorie T. Nieh, and Thomas C. Flood. 1972. Lower valent tungsten halides. New class of reagents for deoxygenation of organic molecules. ''J. Am. Chem. Soc.'' 94(18): 6538-6540. (doi:10.1021/ja00773a045.)</ref>
+
* Reduction with [[tungsten hexachloride]] and [[N-Butyllithium|''n''-butyllithium]] generates the [[alkene]]. This reaction in effect is a '''de-epoxidation''':<ref>K. Barry Sharpless, Martha A. Umbreit, Marjorie T. Nieh, and Thomas C. Flood, Lower valent tungsten halides. New class of reagents for deoxygenation of organic molecules. ''J. Am. Chem. Soc.'' 94(18): 6538-6540.</ref>
  
 
:[[Image:De-epoxidation.png|400px|De-epoxidation with tungsten hexachloride / n-butyllithium.]]
 
:[[Image:De-epoxidation.png|400px|De-epoxidation with tungsten hexachloride / n-butyllithium.]]
  
 
== See also ==
 
== See also ==
 
 
* [[Alcohol]]
 
* [[Alcohol]]
 
* [[Epoxy]]
 
* [[Epoxy]]
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* [[Ethylene glycol]]
 
* [[Ethylene glycol]]
 
* [[Ethylene oxide]]
 
* [[Ethylene oxide]]
 +
* [[Polyethylene glycol]]
  
 
== Notes ==
 
== Notes ==
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== References ==
 
== References ==
 
+
* March, Jerry. ''Advanced Organic Chemistry: Reactions, Mechanisms and Structure,'' 3rd ed. John Wiley & Sons, 1985. ISBN 0471854727.
* March, Jerry. 1985. ''Advanced Organic Chemistry: Reactions, Mechanisms and Structure.'' 3rd ed. John Wiley & Sons. ISBN 0471854727.
+
* McMurry, John. ''Organic Chemistry,'' 6th ed. Belmont, CA: Thomson, 2004. ISBN 0534420052.
 
+
* Morrison, Robert T., and Robert N. Boyd. ''Organic Chemistry,'' 6th ed. Englewood Cliffs, NJ: Prentice Hall, 1992. ISBN 0136436692.
* McMurry, John. 2004. ''Organic Chemistry.'' 6th ed. Belmont, CA: Brooks/Cole. ISBN 0534420052.
+
* Solomons, T.W. Graham, and Craig B. Fryhle. ''Organic Chemistry,'' 8th ed. Hoboken, NJ: John Wiley, 2004. ISBN 0471417998.
 
+
* Streitwieser, Andrew, and Clayton H. Heathcock. ''Introduction to Organic Chemistry.'' New York: Macmillan, 1976. ISBN 0024180106.
* Morrison, Robert T., and Robert N. Boyd. 1992. ''Organic Chemistry.'' 6th ed. Englewood Cliffs, NJ: Prentice Hall. ISBN 0136436692.
 
 
 
* Solomons, T.W. Graham, and Craig B. Fryhle. 2004. ''Organic Chemistry.'' 8th ed. Hoboken, NJ: John Wiley. ISBN 0471417998.
 
 
 
* Streitwieser, Andrew, and Clayton H. Heathcock. 1976. ''Introduction to Organic Chemistry.'' New York: Macmillan. ISBN 0024180106.
 
  
 
== External links ==
 
== External links ==
 
+
All links retrieved August 19, 2017.
* [http://www.cem.msu.edu/~reusch/VirtualText/alcohol2.htm The Chemistry of Epoxides]. Retrieved September 22, 2008.
+
* [http://www.cem.msu.edu/~reusch/VirtualText/alcohol2.htm Oxidation of Alcohols].
 
+
* [http://chemistry2.csudh.edu/rpendarvis/EtherSH.html#epox Alcohols as Acids, Ethers and Thiols].  
* [http://chemistry2.csudh.edu/rpendarvis/EtherSH.html#epox Alcohols as Acids, Ethers and Thiols]. Retrieved September 22, 2008.
+
* [http://www.anpro.com/support/MSDS.pdf Material Safety Data Sheet: Ethylene Oxide] Andersen Sterilizers, Haw River, NC.  
 
+
* [http://www.cdc.gov/niosh/topics/ethyleneoxide/ Ethylene Oxide] National Institute for Occupational Safety and Health.  
* Australian Government, Department of the Environment, Water, Heritage, and the Arts. June 2004. [http://www.npi.gov.au/database/substance-info/profiles/42.html National Pollutant Inventory: Ethylene oxide fact sheet] Retrieved September 22, 2008.
 
 
 
* American Chemistry. 2007. [http://www.americanchemistry.com/s_acc/sec_CPT.asp?SID=1&DID=5431&CID=1467&VID=238&RTID=0&CIDQS=&Taxonomy=&specialSearch= What is Ethylene Oxide?] Retrieved September 22, 2008.
 
 
 
* [http://www.anpro.com/support/MSDS.pdf Material Safety Data Sheet: Ethylene Oxide] Andersen Sterilizers, Haw River, NC. Retrieved September 22, 2008.
 
 
 
* [http://www.cdc.gov/niosh/topics/ethyleneoxide/ Ethylene Oxide] National Institute for Occupational Safety and Health. Retrieved September 22, 2008.
 
  
 
[[Category:Physical sciences]]
 
[[Category:Physical sciences]]

Revision as of 22:29, 11 February 2022

A ball-and-stick model of ethylene oxide, the simplest epoxide.

An epoxide is a cyclic ether with only three ring atoms. The simplest epoxide is ethylene oxide, also known as oxirane, which is regarded as the "parent" compound. Thus, members of the class of epoxides are also called oxiranes. Epoxides are more reactive than ordinary ethers.

A polymer containing unreacted epoxide units is called a polyepoxide or an epoxy. Epoxy resins are used as adhesives and structural materials. Polymerization of an epoxide gives a polyether. For example, polymerization of ethylene oxide generates polyethylene glycol, also known as polyethylene oxide, which is commercially the most important form of polyether.

Nomenclature

Simple epoxides are named from the parent compound oxirane (ethylene oxide), such as in chloromethyloxirane. When epoxide is considered a functional group in a larger compound, it is referred to with the epoxy prefix. An example is the compound 1,2-epoxycycloheptane, which can also be called cycloheptene epoxide.

A polymer containing unreacted epoxide units is called a polyepoxide or an epoxy.

Synthesis

Epoxides are usually produced by one of the reactions given below.

Olefin peroxidation

Olefin peroxidation, also known as the Prilezhaev reaction,[1] involves oxidation of an alkene with a peroxide, usually a peroxyacid like meta-chloroperoxybenzoic acid (m-CPBA) or with a dioxirane such as dimethyldioxirane (DMDO). An example is the epoxidation of styrene with perbenzoic acid to styrene oxide:[2]

Prilezhaev Reaction.

The reaction proceeds via what is commonly known as the Butterfly Mechanism.[3] It is easiest to consider the oxygen as an electrophile and the alkene as a nucleophile, although they both operate in that capacity, and the reaction is thought to be concerted. (The numbers in the mechanism below are for simplification.)

Butterfly Mechanism

Related processes include some catalytic enantioselective reactions, such as the:

  • Sharpless epoxidation
  • Jacobsen epoxidation
  • Shi epoxidation

Intramolecular SN2 substitution

This method is a variant of the Williamson ether synthesis. In this case, the alkoxide ion and the halide are right next to each other in the same molecule (such compounds are generically called halohydrins), which makes this a simple ring closure reaction. For example, with 2-chloropropanol:[4]

Methyloxirane from 2-chloroproprionic acid.png

Johnson-Corey-Chaykovsky reaction

In the Johnson-Corey-Chaykovsky reaction, epoxides are generated from carbonyl groups and sulfonium ylides.

Reactions

The three-membered ring of epoxide is approximately an equilateral triangle, that is, its bond angles are about 60°, which makes it highly strained. The strained ring makes epoxides more reactive than other ethers, especially towards nucleophiles. Typical epoxide reactions are noted below.

  • Nucleophilic addition to an epoxide can be catalyzed by a base or an acid.
EpoxOpen.png
  • Under acidic conditions, the nucleophile attacks the carbon that will form the most stable carbocation, that is, the most substituted carbon (similar to a halonium ion). Under basic conditions, the nucleophile attacks the least substituted carbon, in accordance with standard SN2 nuclephilic addition reaction process.
  • Hydrolysis of an epoxide in presence of an acid catalyst generates a glycol. The hydrolysis process of epoxides can be considered to be the nucleophilic addition of water to the epoxide under acidic conditions.
  • Reduction of an epoxide with lithium aluminum hydride and water generates an alcohol. This reduction process can be considered to be the nucleophilic addition of hydride (H-) to the epoxide under basic conditions.
  • Reduction with tungsten hexachloride and n-butyllithium generates the alkene. This reaction in effect is a de-epoxidation:[5]
De-epoxidation with tungsten hexachloride / n-butyllithium.

See also

Notes

  1. Jerry March, Advanced Organic Chemistry: Reactions, Mechanisms and Structure, 3rd edition. (John Wiley & Sons, 1985, ISBN 0471854727).
  2. Harold Hibbert and Pauline Burt, Styrene Oxide, Org. Synth. Coll. Vol. 1: 494. Retrieved September 22, 2008.
  3. Bartlett, Rec. Chem. Prog 11:47.
  4. B. Koppenhoefer and V. Schurig, (R)-Alkyloxiranes of High Enantiomeric Purity from (S)-2-Chloroalkanoic Acids via (S)-2-Chloro-1-Alkanols: (R)-Methyloxirane, Org. Synth. Coll. Vol. 8: 434. Retrieved September 22, 2008.
  5. K. Barry Sharpless, Martha A. Umbreit, Marjorie T. Nieh, and Thomas C. Flood, Lower valent tungsten halides. New class of reagents for deoxygenation of organic molecules. J. Am. Chem. Soc. 94(18): 6538-6540.

References
ISBN links support NWE through referral fees

  • March, Jerry. Advanced Organic Chemistry: Reactions, Mechanisms and Structure, 3rd ed. John Wiley & Sons, 1985. ISBN 0471854727.
  • McMurry, John. Organic Chemistry, 6th ed. Belmont, CA: Thomson, 2004. ISBN 0534420052.
  • Morrison, Robert T., and Robert N. Boyd. Organic Chemistry, 6th ed. Englewood Cliffs, NJ: Prentice Hall, 1992. ISBN 0136436692.
  • Solomons, T.W. Graham, and Craig B. Fryhle. Organic Chemistry, 8th ed. Hoboken, NJ: John Wiley, 2004. ISBN 0471417998.
  • Streitwieser, Andrew, and Clayton H. Heathcock. Introduction to Organic Chemistry. New York: Macmillan, 1976. ISBN 0024180106.

External links

All links retrieved August 19, 2017.

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