Ketene: Difference between revisions

Content deleted Content added

Inline

Latest revision as of 08:34, 14 November 2024

In organic chemistry, a ketene is an organic compound of the form RR'C=C=O, where R and R' are two arbitrary monovalent chemical groups (or two separate substitution sites in the same molecule).^[1] The name may also refer to the specific compound ethenone H₂C=C=O, the simplest ketene.^[2]

Although they are highly useful, most ketenes are unstable. When used as reagents in a chemical procedure, they are typically generated when needed, and consumed as soon as (or while) they are produced.^[1]

History

Ketenes were first studied as a class by Hermann Staudinger before 1905.^[3]

Ketenes were systematically investigated by Hermann Staudinger in 1905 in the form of diphenylketene (conversion of $\alpha$ -chlorodiphenyl acetyl chloride with zinc). Staudinger was inspired by the first examples of reactive organic intermediates and stable radicals discovered by Moses Gomberg in 1900 (compounds with triphenylmethyl group).^[4]

Properties

Ketenes are highly electrophilic at the carbon atom bonded with the heteroatom, due to its sp character. Ketene can be formed with different heteroatom bonded to the sp carbon atom, such as O, S or Se, respectively named ketene, thioketene and selenoketene.

Ethenone, the simplest ketene, has different experimental lengths for each of the double bonds; the C=O bond is 1,160Å and the C=C bond is 1,314Å. The angle between the two H atoms is 121.5°, similar to the theoretically ideal angle formed in alkenes between sp² carbon atom and H substituents.^[5]

Ketenes are unstable and cannot be stored. In the absence of nucleophiles with which to react, ethenone dimerises to give β-lactone, a cyclic ester. If the ketene is disubstituted, the dimerisation product is a substituted cyclobutadione. For monosubstituted ketenes, the dimerisation could afford either the ester or the diketone product.

Synthesis

Ketene is produced on a commercial scale by thermal dehydration of acetic acid. Substituted ketenes can be prepared from acyl chlorides by an elimination reaction in which HCl is lost:

Formation of a ketene from an acyl chloride.

In this reaction, a base, usually triethylamine, removes the acidic proton alpha to the carbonyl group, inducing the formation of the carbon-carbon double bond and the loss of a chloride ion:

Ketenes can also be formed from α-diazoketones by the Wolff rearrangement, and from vinylene carbonate by phosphorus(V) sulfide and irradiation.^[6]

Another way to generate ketenes is through flash vacuum thermolysis (FVT) with 2-pyridylamines. Plüg and Wentrup developed a method in 1997 that improved on FVT reactions to produce ketenes with a stable FVT that is moisture insensitive, using mild conditions (480 °C). The N-pyridylamines are prepared via a condensation with R-malonates with N-amino(pyridene) and DCC as the solvent.^[7]

A more robust method for preparing ketenes is the carbonylation of metal-carbenes, and in situ reaction of the thus produced highly reactive ketenes with suitable reagents such as imines, amines, or alcohols.^[8] This method is an efficient one‐pot tandem protocol of the carbonylation of α‐diazocarbonyl compounds and a variety of N‐tosylhydrazones catalysed by Co(II)–porphyrin metalloradicals leading to the formation of ketenes, which subsequently react with a variety of nucleophiles and imines to form esters, amides and β‐lactams. This system has a broad substrate scope and can be applied to various combinations of carbene precursors, nucleophiles and imines.^[9]

Ethenone can be produced through pyrolysis of acetone vapours over a hot filament in an apparatus that was eventually developed into the "ketene lamp" or "Hurd lamp" (named for Charles D. Hurd).^[10]

Reactions and applications

Due to their cumulated double bonds, ketenes are very reactive.^[11]

Formation of carboxylic acid esters

By reaction with alcohols, carboxylic acid esters are formed:

Formation of carboxylic anhydrides

Ketenes react with a carboxylic acids to form carboxylic acid anhydrides:

Formation of amides

Ketenes react with ammonia and amines to give the corresponding amides:

Hydrolysis

By reaction with water, carboxylic acids are formed from ketenes

Formation of enol esters

Enol esters are formed from ketenes with enolisable carbonyl compounds. The following example shows the reaction of ethenone with acetone to form a propen-2-yl acetate:

Dimerisation

At room temperature, ketene quickly dimerizes to diketene, but the ketene can be recovered by heating:

[2+2]-cycloaddition

Ketenes can react with alkenes, carbonyl compounds, carbodiimides and imines in a [2+2] cycloaddition. The example shows the synthesis of a β-lactam by the reaction of a ketene with an imine (see Staudinger synthesis):^[12]^[13]

Applications

Ketenes are generally very reactive, and participate in various cycloadditions. One important process is the dimerization to give propiolactones. A specific example is the dimerization of the ketene of stearic acid to afford alkyl ketene dimers, which are widely used in the paper industry.^[1] AKD's react with the hydroxyl groups on the cellulose via esterification reaction.

They will also undergo [2+2] cycloaddition reactions with electron-rich alkynes to form cyclobutenones, or carbonyl groups to form beta-lactones. With imines, beta-lactams are formed. This is the Staudinger synthesis, a facile route to this important class of compounds. With acetone, ketene reacts to give isopropenyl acetate.^[1]

A variety of hydroxylic compounds can add as nucleophiles, forming either enol or ester products. As examples, a water molecule easily adds to ketene to give 1,1-dihydroxyethene and acetic anhydride is produced by the reaction of acetic acid with ketene. Reactions between diols (HO−R−OH) and bis-ketenes (O=C=CH−R'−CH=C=O) yield polyesters with a repeat unit of (−O−R−O−CO−R'−CO).

Ethyl acetoacetate, an important starting material in organic synthesis, can be prepared using a diketene in reaction with ethanol. They directly form ethyl acetoacetate, and the yield is high when carried out under controlled circumstances; this method is therefore used industrially.

References

^ ^a ^b ^c ^d Miller R, Abaecherli C, Said A, Jackson B (2001). "Ketenes". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a15_063. ISBN 978-3527306732.
^ Saul Patai, ed. (1980). Ketenes, Allenes and Related Compounds: Part 1, Volume 1. PATAI'S Chemistry of Functional Groups. John Wiley & Sons. doi:10.1002/9780470771600. ISBN 9780470771600.Saul Patai, ed. (1980). Ketenes, Allenes and Related Compounds: Part 2, Volume 2. PATAI'S Chemistry of Functional Groups. John Wiley & Sons. doi:10.1002/9780470771617. ISBN 9780471276708.
^ Staudinger H (1905). "Ketene, eine neue Körperklasse" [Ketenes, a new class of substances]. Berichte der Deutschen Chemischen Gesellschaft. 38 (2): 1735–1739. doi:10.1002/cber.19050380283.
^ Thomas T. Tidwell, The first century of Ketenes (1905-2005): the birth of a family of reactive intermediates, Angewandte Chemie, Int. Edition, Band 44, 2005, S. 5778–5785
^ Ma NL, Wong M (2000). "A Theoretical Study of the Properties and Reactivities of Ketene, Thioketene, and Selenoketene". European Journal of Organic Chemistry. 2000 (8): 1411_1421. doi:10.1002/(SICI)1099-0690(200004)2000:8<1411::AID-EJOC1411>3.0.CO;2-N.
^ Handbook of Reagents for Organic Syntheses, Sulfur-Containing Reagents, ed. L.A. Paquette, Wiley-VCH, 2010, ISBN 978-0-470-74872-5, p. 535.
^ Carsten Plüg ,Hussein Kanaani and Curt Wentrup (12 February 2015). "Ketenes from N-(2-Pyridyl)amides". Australian Journal of Chemistry. 68 (4): 687. doi:10.1071/CH14714.
^ Paul ND, Chirila A, Lu H, Zhang XP, de Bruin B (September 2013). "Carbene radicals in cobalt(II)-porphyrin-catalysed carbene carbonylation reactions; a catalytic approach to ketenes". Chemistry: A European Journal. 19 (39): 12953–8. doi:10.1002/chem.201301731. PMC 4351769. PMID 24038393.
^ Chirila A, van Vliet KM, Paul ND, de Bruin B (2018). "[Co(MeTAA)] Metalloradical Catalytic Route to Ketenes via Carbonylation of Carbene Radicals" (PDF). European Journal of Inorganic Chemistry. 2018 (20–21): 2251–2258. doi:10.1002/ejic.201800101. ISSN 1099-0682.
^ Tidwell, Thomas T. (2005-09-12). "The First Century of Ketenes (1905–2005): The Birth of a Versatile Family of Reactive Intermediates". Angewandte Chemie International Edition. 44 (36): 5778–5785. doi:10.1002/anie.200500098. ISSN 1433-7851.
^ Siegfried Hauptmann (1985), Organische Chemie: mit 65 Tabellen (in German), Leipzig: Deutscher Verlag für Grundstoffindustrie, pp. 410–412, ISBN 3871449024
^ Jie Jack Li (2006), Name reactions. A collection of detailed reaction mechanisms (in German) (3 ed.), Berlin: Springer-Verlag, pp. 561-562, doi:10.1007/3-540-30031-7, ISBN 9783540300304
^ Hermann Staudinger (1907), "Zur Kenntnis der Ketene. Diphenylketen", Justus Liebigs Annalen der Chemie (in German), vol. 356, no. 1–2, John Wiley & Sons, Inc., pp. 51–123, doi:10.1002/jlac.19073560106

External links

Media related to Ketenes at Wikimedia Commons

[Ullmann-1] Miller R, Abaecherli C, Said A, Jackson B (2001). "Ketenes". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a15_063. ISBN 978-3527306732.

[2] Saul Patai, ed. (1980). Ketenes, Allenes and Related Compounds: Part 1, Volume 1. PATAI'S Chemistry of Functional Groups. John Wiley & Sons. doi:10.1002/9780470771600. ISBN 9780470771600.Saul Patai, ed. (1980). Ketenes, Allenes and Related Compounds: Part 2, Volume 2. PATAI'S Chemistry of Functional Groups. John Wiley & Sons. doi:10.1002/9780470771617. ISBN 9780471276708.

[3] Staudinger H (1905). "Ketene, eine neue Körperklasse" [Ketenes, a new class of substances]. Berichte der Deutschen Chemischen Gesellschaft. 38 (2): 1735–1739. doi:10.1002/cber.19050380283.

[4] Thomas T. Tidwell, The first century of Ketenes (1905-2005): the birth of a family of reactive intermediates, Angewandte Chemie, Int. Edition, Band 44, 2005, S. 5778–5785

[5] Ma NL, Wong M (2000). "A Theoretical Study of the Properties and Reactivities of Ketene, Thioketene, and Selenoketene". European Journal of Organic Chemistry. 2000 (8): 1411_1421. doi:10.1002/(SICI)1099-0690(200004)2000:8<1411::AID-EJOC1411>3.0.CO;2-N.

[6] Handbook of Reagents for Organic Syntheses, Sulfur-Containing Reagents, ed. L.A. Paquette, Wiley-VCH, 2010, ISBN 978-0-470-74872-5, p. 535.

[7] Carsten Plüg ,Hussein Kanaani and Curt Wentrup (12 February 2015). "Ketenes from N-(2-Pyridyl)amides". Australian Journal of Chemistry. 68 (4): 687. doi:10.1071/CH14714.

[8] Paul ND, Chirila A, Lu H, Zhang XP, de Bruin B (September 2013). "Carbene radicals in cobalt(II)-porphyrin-catalysed carbene carbonylation reactions; a catalytic approach to ketenes". Chemistry: A European Journal. 19 (39): 12953–8. doi:10.1002/chem.201301731. PMC 4351769. PMID 24038393.

[9] Chirila A, van Vliet KM, Paul ND, de Bruin B (2018). "[Co(MeTAA)] Metalloradical Catalytic Route to Ketenes via Carbonylation of Carbene Radicals" (PDF). European Journal of Inorganic Chemistry. 2018 (20–21): 2251–2258. doi:10.1002/ejic.201800101. ISSN 1099-0682.

[10] Tidwell, Thomas T. (2005-09-12). "The First Century of Ketenes (1905–2005): The Birth of a Versatile Family of Reactive Intermediates". Angewandte Chemie International Edition. 44 (36): 5778–5785. doi:10.1002/anie.200500098. ISSN 1433-7851.

[:1-11] Siegfried Hauptmann (1985), Organische Chemie: mit 65 Tabellen (in German), Leipzig: Deutscher Verlag für Grundstoffindustrie, pp. 410–412, ISBN 3871449024

[:2-12] Jie Jack Li (2006), Name reactions. A collection of detailed reaction mechanisms (in German) (3 ed.), Berlin: Springer-Verlag, pp. 561-562, doi:10.1007/3-540-30031-7, ISBN 9783540300304

[:3-13] Hermann Staudinger (1907), "Zur Kenntnis der Ketene. Diphenylketen", Justus Liebigs Annalen der Chemie (in German), vol. 356, no. 1–2, John Wiley & Sons, Inc., pp. 51–123, doi:10.1002/jlac.19073560106

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

@@ Line 1: / Line 1: @@
+{{short description|1=Organic compound of the form >C=C=O}}
 {{About|the generic structure class|the specific chemical of this name|ethenone}}
-[[File:Ketenes.png|thumb|General formula for a ketene.]]
+[[File:Ketenes nonsymmetric.png|thumb|General formula for a ketene]]
-A '''ketene''' is an [[organic compound]] of the form R′R″C=C=O, where R and R' are two arbitrary [[valence (chemistry)|monovalent]] [[functional group|chemical groups]] (or two separate substitution sites in the same molecule).<ref name="Ullmann"/> The name may also refers to the specific compound [[ethenone]] {{chem2|H2C\dC\dO}}, the simplest ketene.
+In [[organic chemistry]], a '''ketene''' is an [[organic compound]] of the form {{chem2|RR'C\dC\dO}}, where R and R' are two arbitrary [[valence (chemistry)|monovalent]] [[functional group|chemical groups]] (or two separate [[Substituent|substitution sites]] in the same molecule).<ref name="Ullmann"/> The name may also refer to the specific compound [[ethenone]] {{chem2|H2C\dC\dO}}, the simplest ketene.<ref>{{cite book|title=Ketenes, Allenes and Related Compounds: Part 1, Volume 1|year=1980|editor=Saul Patai|isbn= 9780470771600|doi=10.1002/9780470771600|publisher=John Wiley & Sons|series=PATAI'S Chemistry of Functional Groups}}{{cite book|title=Ketenes, Allenes and Related Compounds: Part 2, Volume 2|year=1980|editor=Saul Patai|isbn= 9780471276708|doi=10.1002/9780470771617|publisher=John Wiley & Sons|series=PATAI'S Chemistry of Functional Groups}}</ref>
-Although they are highly useful, most ketenes are [[chemical stability|unstable]].  When used as [[reagent]]s in a chemical procedure, they are typically generated when needed, and consumed as soon as (or while) they are produced.<ref name="Ullmann">{{Cite book |title=Ullmann's Encyclopedia of Industrial Chemistry |last=Miller |first=Raimund |last2=Abaecherli |first2=Claudio |last3=Said |first3=Adel |last4=Jackson |first4=Barry | name-list-format = vanc |year=2001 |isbn=978-3527306732 |chapter=Ketenes |doi=10.1002/14356007.a15_063}}</ref>
+Although they are highly useful, most ketenes are [[chemical stability|unstable]].  When used as [[reagent]]s in a chemical procedure, they are typically generated when needed, and consumed as soon as (or while) they are produced.<ref name="Ullmann">{{Cite book |title=Ullmann's Encyclopedia of Industrial Chemistry |last1=Miller |first1=Raimund |last2=Abaecherli |first2=Claudio |last3=Said |first3=Adel |last4=Jackson |first4=Barry | name-list-style = vanc |year=2001 |isbn=978-3527306732 |chapter=Ketenes |doi=10.1002/14356007.a15_063}}</ref>
 ==History==
-Ketenes were first studied as a class by [[Hermann Staudinger]] before 1905.<ref>{{Cite journal | first = Hermann | last = Staudinger | name-list-format = vanc |year=1905 |title=Ketene, eine neue Körperklasse |trans-title=Ketenes, a new class of substances |url=http://babel.hathitrust.org/cgi/pt?id=uc1.b3481909;view=1up;seq=483 |journal=Berichte der Deutschen Chemischen Gesellschaft |volume=38 |issue=2 |pages=1735–1739 |doi=10.1002/cber.19050380283}}</ref>
+Ketenes were first studied as a class by [[Hermann Staudinger]] before 1905.<ref>{{Cite journal | first = Hermann | last = Staudinger | name-list-style = vanc |year=1905 |title=Ketene, eine neue Körperklasse |trans-title=Ketenes, a new class of substances |url=http://babel.hathitrust.org/cgi/pt?id=uc1.b3481909;view=1up;seq=483 |journal=Berichte der Deutschen Chemischen Gesellschaft |volume=38 |issue=2 |pages=1735–1739 |doi=10.1002/cber.19050380283}}</ref>
 Ketenes were systematically investigated by Hermann Staudinger in 1905 in the form of diphenylketene (conversion of <math>\alpha</math>-chlorodiphenyl acetyl chloride with zinc). Staudinger was inspired by the first examples of reactive organic intermediates and stable radicals discovered by [[Moses Gomberg]] in 1900 (compounds with triphenylmethyl group).<ref>Thomas T. Tidwell, The first century of Ketenes (1905-2005): the birth of a family of reactive intermediates, Angewandte Chemie, Int. Edition, Band 44, 2005, S. 5778–5785</ref>
-==Preparation==
+==Properties==
+Ketenes are highly electrophilic at the carbon atom bonded with the heteroatom, due to its ''sp'' character. Ketene can be formed with different heteroatom bonded to the ''sp'' carbon atom, such as [[oxygen|O]], [[sulphur|S]] or [[selenium|Se]], respectively named ketene, [[thioketene]] and selenoketene.
-Ethenone, the simplest ketene can be generated by [[pyrolysis]] (thermal cracking) of [[acetone]]:<ref>{{Cite book |title=Weygand/Hilgetag Preparative Organic Chemistry | vauthors = Weygand C |date=1972 |publisher=John Wiley & Sons, Inc. |isbn=978-0471937494 | veditors = Hilgetag G, Martini A |edition=4th |location=New York |pages=1031–1032 }}</ref>
-:CH<sub>3</sub>−CO−CH<sub>3</sub>  → CH<sub>2</sub>=C=O + CH<sub>4</sub>
-This reaction is called the [[Schmidlin ketene synthesis]].<ref>{{cite book | chapter = Ketene in Organic Syntheses | title = Organic Syntheses | vauthors = Hurd CD, Kamm O | volume = Collective Vol. 1 | pages = 330 | date = 1941 | chapter-url = http://www.orgsyn.org/demo.aspx?prep=cv1p0330 }}</ref><ref>{{cite journal | first1 = Julius | last1 = Schmidlin | first2 = Maximilian | last2 = Bergman | name-list-format = vanc | date = 1910 | url = http://babel.hathitrust.org/cgi/pt?id=uc1.b3481275;view=1up;seq=565 | title = Darstellung des Ketens aus Aceton | trans-title = Preparation of ketene from acetone | language = German | journal = Berichte der Deutschen Chemischen Gesellschaft | volume = 43 | issue = 3| pages = 2821–2823 | doi=10.1002/cber.19100430340}}</ref>
+[[Ethenone]], the simplest ketene, has different experimental lengths for each of the double bonds; the C=O bond is 1,160[[Angstrom|Å]] and the C=C bond is 1,314Å. The angle between the two [[Hydrogen|H]] atoms is 121.5°, similar to the theoretically ideal angle formed in [[alkene]]s between ''sp<sup>2</sup> ''carbon atom and H substituents.<ref>{{Cite journal | first1 = Ngai Ling | last1 = Ma |first2 = MingWah | last2 = Wong | name-list-style = vanc |year=2000 |title=A Theoretical Study of the Properties and Reactivities of Ketene, Thioketene, and Selenoketene|url=https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/(SICI)1099-0690(200004)2000:8%3C1411::AID-EJOC1411%3E3.0.CO;2-N |journal=European Journal of Organic Chemistry |volume=2000 |issue=8 |pages=1411_1421 |doi=10.1002/(SICI)1099-0690(200004)2000:8<1411::AID-EJOC1411>3.0.CO;2-N}}</ref>
-Other ketenes can be prepared from [[acyl chloride]]s by an [[elimination reaction]] in which [[hydrogen chloride|HCl]] is lost:
+Ketenes are unstable and cannot be stored. In the absence of nucleophiles with which to react, ethenone dimerises to give β-[[lactone]], a cyclic [[ester]]. If the ketene is disubstituted, the dimerisation product is a substituted cyclobutadione. For monosubstituted ketenes, the dimerisation could afford either the ester or the diketone product.
+==Synthesis==
+Ketene is produced on a commercial scale by thermal dehydration of [[acetic acid]]. Substituted ketenes can be prepared from [[acyl chloride]]s by an [[elimination reaction]] in which [[hydrogen chloride|HCl]] is lost:
 :[[File:Mecanisme-de-la-formation-des-cetenes.png|none|Formation of a ketene from an acyl chloride.]]
@@ Line 22: / Line 27: @@
 [[File:Ketene Synthesis.png|370px|Synthesis of Ketene]]
-Ketenes can also be formed from α-[[diazoketone]]s by [[Wolff rearrangement]].
+Ketenes can also be formed from α-[[diazoketone]]s by the [[Wolff rearrangement]], and from [[vinylene carbonate]] by [[phosphorus(V) sulfide]] and irradiation.<ref>Handbook of Reagents for Organic Syntheses, ''Sulfur-Containing Reagents'', ed. L.A. Paquette, Wiley-VCH, 2010, {{ISBN|978-0-470-74872-5}}, p.&nbsp;535.</ref>
-Another way to generate ketenes is through [[flash vacuum thermolysis]] (FVT) with 2-[[pyridylamine]]s. Plüg and Wentrup developed a method in 1997 that improved on FVT reactions to produce ketenes with a stable FVT  that is moisture insensitive, using mild conditions (480&nbsp;°C). The N-pyridylamines are prepared via a condensation with R-[[malonate]]s with N-amino([[pyridene]]) and [[N,N'-Dicyclohexylcarbodiimide|DCC]] as the solvent.<ref>{{Cite journal |last=Carsten Plüg ,Hussein Kanaani and Curt Wentrup |date=12 February 2015 |title=Ketenes from N-(2-Pyridyl)amides |journal=Australian Journal of Chemistry |volume=68 |issue=4 |pages=687 |doi=10.1071/CH14714 }}</ref>
+Another way to generate ketenes is through [[flash vacuum thermolysis]] (FVT) with 2-[[pyridylamine]]s. Plüg and Wentrup developed a method in 1997 that improved on FVT reactions to produce ketenes with a stable FVT that is moisture insensitive, using mild conditions (480&nbsp;°C). The N-pyridylamines are prepared via a condensation with R-[[malonate]]s with N-amino([[pyridene]]) and [[N,N'-Dicyclohexylcarbodiimide|DCC]] as the solvent.<ref>{{Cite journal |last=Carsten Plüg ,Hussein Kanaani and Curt Wentrup |date=12 February 2015 |title=Ketenes from N-(2-Pyridyl)amides |journal=Australian Journal of Chemistry |volume=68 |issue=4 |pages=687 |doi=10.1071/CH14714 }}</ref>
-A more robust method for preparing ketenes is the [[carbonylation]] of [[Transition metal carbene complex|metal-carbenes]], and “in situ” reaction of the thus produced highly reactive ketenes with suitable reagents such as [[Imine|imines]], [[Amine|amines]], or [[Alcohol|alcohols]].<ref>{{cite journal | vauthors = Paul ND, Chirila A, Lu H, Zhang XP, de Bruin B | title = Carbene radicals in cobalt(II)-porphyrin-catalysed carbene carbonylation reactions; a catalytic approach to ketenes | journal = Chemistry | volume = 19 | issue = 39 | pages = 12953–8 | date = September 2013 | pmid = 24038393 | pmc = 4351769 | doi = 10.1002/chem.201301731 }}</ref> This method is an efficient [[One-pot synthesis|one‐pot]] tandem protocol of the carbonylation of α‐diazocarbonyl compounds and a variety of ''N''‐tosylhydrazones catalysed by Co(II)–[[porphyrin]] metalloradicals leading to the formation of ketenes, which subsequently react with a variety of [[Nucleophile|nucleophiles]] and [[Imine|imines]] to form [[Ester|esters]], [[Amide|amides]] and [[Beta-lactam|β‐lactams]]. This system has a broad substrate scope and can be applied to various combinations of [[carbene]] precursors, nucleophiles and [[Imine|imines]].<ref>{{Cite journal| vauthors = Chirila A, van Vliet KM, Paul ND, de Bruin B |date=2018|title=[Co(MeTAA)] Metalloradical Catalytic Route to Ketenes via Carbonylation of Carbene Radicals|journal=European Journal of Inorganic Chemistry|language=en|volume=2018|issue=20–21|pages=2251–2258|doi=10.1002/ejic.201800101|issn=1099-0682|url=https://pure.uva.nl/ws/files/34388611/Chirila_et_al_2018_European_Journal_of_Inorganic_Chemistry.pdf}}</ref>
+A more robust method for preparing ketenes is the [[carbonylation]] of [[Transition metal carbene complex|metal-carbenes]], and ''in situ'' reaction of the thus produced highly reactive ketenes with suitable reagents such as [[imines]], [[amines]], or [[alcohols]].<ref>{{cite journal | vauthors = Paul ND, Chirila A, Lu H, Zhang XP, de Bruin B | title = Carbene radicals in cobalt(II)-porphyrin-catalysed carbene carbonylation reactions; a catalytic approach to ketenes | journal = Chemistry: A European Journal | volume = 19 | issue = 39 | pages = 12953–8 | date = September 2013 | pmid = 24038393 | pmc = 4351769 | doi = 10.1002/chem.201301731}}</ref> This method is an efficient [[One-pot synthesis|one‐pot]] tandem protocol of the carbonylation of α‐diazocarbonyl compounds and a variety of ''N''‐tosylhydrazones catalysed by Co(II)–[[porphyrin]] metalloradicals leading to the formation of ketenes, which subsequently react with a variety of [[nucleophile]]s and imines to form [[esters]], [[amides]] and [[Beta-lactam|β‐lactams]]. This system has a broad substrate scope and can be applied to various combinations of [[carbene]] precursors, nucleophiles and imines.<ref>{{Cite journal| vauthors = Chirila A, van Vliet KM, Paul ND, de Bruin B |date=2018|title=[Co(MeTAA)] Metalloradical Catalytic Route to Ketenes via Carbonylation of Carbene Radicals|journal=European Journal of Inorganic Chemistry|language=en|volume=2018|issue=20–21|pages=2251–2258|doi=10.1002/ejic.201800101|issn=1099-0682|url=https://pure.uva.nl/ws/files/34388611/Chirila_et_al_2018_European_Journal_of_Inorganic_Chemistry.pdf|doi-access=free}}</ref>
+[[Ethenone]] can be produced through [[pyrolysis]] of [[acetone]] vapours over a hot filament in an apparatus that was eventually developed into the "ketene lamp" or "Hurd lamp" (named for Charles D. Hurd).<ref>{{Cite journal |last=Tidwell |first=Thomas T. |date=2005-09-12 |title=The First Century of Ketenes (1905–2005): The Birth of a Versatile Family of Reactive Intermediates |url=https://onlinelibrary.wiley.com/doi/10.1002/anie.200500098 |journal=Angewandte Chemie International Edition |language=en |volume=44 |issue=36 |pages=5778–5785 |doi=10.1002/anie.200500098 |issn=1433-7851}}</ref>
 ==Reactions and applications==
-Due to their [[Cumulated double bond|cumulated double bonds]], ketenes are very reactive.<ref name=":1">{{citation|surname1=Siegfried Hauptmann|title=Organische Chemie: mit 65 Tabellen|publisher=Deutscher Verlag für Grundstoffindustrie|location=Leipzig|at=pp.&nbsp;410–412|isbn=3871449024|date=1985|language=German
+Due to their [[cumulated double bond]]s, ketenes are very reactive.<ref name=":1">{{citation|surname1=Siegfried Hauptmann|title=Organische Chemie: mit 65 Tabellen|publisher=Deutscher Verlag für Grundstoffindustrie|location=Leipzig|at=pp.&nbsp;410–412|isbn=3871449024|date=1985|language=de
 }}</ref>
 === Formation of carboxylic acid esters ===
-By reaction with [[Alcohol|alcohols]], [[Carboxylic acid ester|carboxylic acid esters]] are formed:
+By reaction with alcohols, [[carboxylic acid ester]]s are formed:
-: [[File:Ketene_Reaktion1_V1.svg|380x380px|none]]
+:[[File:Ketene_Reaktion1_V1.svg|380x380px|none]]
 === Formation of carboxylic anhydrides ===
-Ketenes react with a carboxylic acids to form [[Carboxylic acid anhydride|carboxylic acid anhydrides]]:
+Ketenes react with a carboxylic acids to form [[carboxylic acid anhydride]]s:
-: [[File:Ketene_Reaktion2_V1.svg|450x450px|none]]
-=== Formation of carboxylic acid amides ===
-Ketenes react with [[ammonia]] to [[Primary amide|primary amides]]:
-: [[File:Ketene_Reaktion3_V1.svg|350x350px|none]]
-The reaction of ketenes with [[primary amines]] produces [[Secondary amide|secondary amides]]:
-:[[File:Ketene Reaktion5 V1.svg|none|frameless|380x380px]]
+:[[File:Ketene_Reaktion2_V1.svg|450x450px|none]]
-Ketenes react with [[secondary amines]] to give tertiary amides:
+=== Formation of amides ===
+Ketenes react with [[ammonia]] and [[amine]]s to give the corresponding [[amide]]s:
 :[[File: Ketene Reaktion4 V1.svg|frameless|none|380x380px]]
@@ Line 60: / Line 58: @@
 :[[File: Ketene Reaktion6 V1.svg|frameless|none|350x350px]]
-=== Formation of enol acetates ===
+=== Formation of enol esters ===
-Enolacetates are formed from ketenes with [[Enol|enolisable]] [[carbonyl compounds]]. The following example shows the reaction of [[ethenone]] with [[acetone]] to form a propen-2-yl acetate:
+Enol esters are formed from ketenes with [[enol]]isable [[carbonyl compounds]]. The following example shows the reaction of [[ethenone]] with [[acetone]] to form a propen-2-yl acetate:
-:[[File: Ketene Reaktion7 V3.svg|frameless|none|480x480px]]
+:[[File: Ketene Reaktion7 V3 unlabeled.svg|frameless|none|480x480px]]
 === Dimerisation ===
-At room temperature, ketene quickly dimerizes to diketene, but the ketene can be recovered by heating:
+At room temperature, ketene quickly dimerizes to [[diketene]], but the ketene can be recovered by heating:
-:[[File: Ketene Reaktion8 V1.svg|frameless|none|380x380px]]
+:[[File:Dimerisation of ketene.png|frameless|Dimerisation of ketene|500px]]
-=== [2+2]-Cycloaddition ===
+=== [2+2]-cycloaddition ===
-Ketenes can react with [[Alkene|alkenes]], [[carbonyl compounds]], [[Carbodiimide|carbodiimides]] and [[Imine|imines]] in the [[Enone–alkene cycloadditions|[2+2] cycloaddition]]. The example shows the synthesis of a [[Beta-lactam|β-lactam]] by the reaction of a ketene with an imine (see [[Staudinger synthesis]]):<ref name=":2">{{citation|surname1=Jie Jack Li|title=Name reactions. A collection of detailed reaction mechanisms|edition=3|publisher=Springer-Verlag|location=Berlin|at=pp.&nbsp;561-562|isbn=9783540300304|date=2006|language=German|doi=10.1007/3-540-30031-7
+Ketenes can react with [[alkenes]], carbonyl compounds, [[carbodiimides]] and imines in a [[Enone–alkene cycloadditions|[2+2] cycloaddition]]. The example shows the synthesis of a [[β-lactam]] by the reaction of a ketene with an imine (see [[Staudinger synthesis]]):<ref name=":2">{{citation|surname1=Jie Jack Li|title=Name reactions. A collection of detailed reaction mechanisms|edition=3|publisher=Springer-Verlag|location=Berlin|at=pp.&nbsp;561-562|isbn=9783540300304|date=2006|language=de|doi=10.1007/3-540-30031-7
-}}</ref><ref name=":3">{{citation|surname1=Hermann Staudinger|periodical=[[Justus Liebigs Annalen der Chemie]]|title=Zur Kenntnis der Ketene. Diphenylketen|volume=356|issue=1–2|publisher=John Wiley & Sons, Inc.|at=pp.&nbsp;51–123|date=1907|language=German|doi=10.1002/jlac.19073560106
+}}</ref><ref name=":3">{{citation|surname1=Hermann Staudinger|periodical=[[Justus Liebigs Annalen der Chemie]]|title=Zur Kenntnis der Ketene. Diphenylketen|volume=356|issue=1–2|publisher=John Wiley & Sons, Inc.|at=pp.&nbsp;51–123|date=1907|language=de|doi=10.1002/jlac.19073560106
 |url=https://zenodo.org/record/1427571}}</ref>
 :[[File:Staudinger-Synthese ÜV6.svg|frameless|none|450x450px]]
 ===Applications===
-Ketenes are generally very reactive, and participate in various [[cycloaddition]]s. One important process is the dimerization to give [[Beta-propiolactone|propiolactone]]s. A specific example is the dimerization of the ketene of [[stearic acid]] to afford [[alkyl ketene dimer]]s, which are widely used in the paper industry.<ref name="Ullmann" /> AKD's react with the hydroxyl groups on the celluose via [[esterification]] reaction.
+Ketenes are generally very reactive, and participate in various [[cycloaddition]]s. One important process is the dimerization to give [[beta-propiolactone|propiolactone]]s. A specific example is the dimerization of the ketene of [[stearic acid]] to afford [[alkyl ketene dimer]]s, which are widely used in the paper industry.<ref name="Ullmann" /> AKD's react with the hydroxyl groups on the cellulose via [[esterification]] reaction.
-They will also undergo [2+2] cycloaddition reactions with electron-rich [[alkyne]]s to form [[cyclobutenone]]s, or carbonyl groups to form beta-[[lactone]]s. With [[imine]]s [[beta-lactam]]s are formed. This is the [[Staudinger synthesis]], a facile route to this important class of compounds.  With [[acetone]], ketene reacts to give [[Isopropenyl acetate]].<ref name="Ullmann" />
+They will also undergo [2+2] cycloaddition reactions with electron-rich [[alkyne]]s to form [[cyclobutenone]]s, or carbonyl groups to form beta-[[lactone]]s. With [[imine]]s, beta-lactams are formed. This is the Staudinger synthesis, a facile route to this important class of compounds. With [[acetone]], ketene reacts to give [[isopropenyl acetate]].<ref name="Ullmann" />
-A variety of [[hydroxyl group|hydroxylic]] compounds can add as nucleophiles, forming either [[enol]] or [[ester]] products. As examples, a water molecule easily adds to ketene to give [[1,1-dihydroxyethene]] and [[acetic anhydride]] is produced by the reaction of [[acetic acid]] with ketene. Reactions between [[diol]]s (HO−R−OH) and bis-ketenes (O=C=CH−R′−CH=C=O) yield [[polyester]]s with a repeat unit of (−O−R−O−CO−R′−CO).
+A variety of [[hydroxyl group|hydroxylic]] compounds can add as nucleophiles, forming either [[enol]] or [[ester]] products. As examples, a water molecule easily adds to ketene to give [[1,1-dihydroxyethene]] and [[acetic anhydride]] is produced by the reaction of [[acetic acid]] with ketene. Reactions between [[diol]]s ({{chem2|HO\sR\sOH}}) and bis-ketenes ({{chem2|O\dC\dCH\sR'\sCH\dC\dO}}) yield [[polyester]]s with a repeat unit of ({{chem2|\sO\sR\sO\sCO\sR'\sCO}}).
 [[Ethyl acetoacetate]], an important starting material in organic synthesis, can be prepared using a [[diketene]] in reaction with [[ethanol]]. They directly form ethyl acetoacetate, and the yield is high when carried out under controlled circumstances; this method is therefore used industrially.
@@ Line 93: / Line 91: @@
 == External links ==
+*{{Commons category-inline}}
-*{{Commonscatinline}}
 {{Molecules detected in outer space}}