Ethenone

Ethenone is a highly reactive gas (at standard conditions) and has a sharp irritating odour. It is only reasonably stable at low temperatures (−80 °C). It must therefore always be prepared for each use and processed immediately, otherwise a dimerization to diketene occurs or it reacts to polymers that are difficult to handle. The polymer content formed during the preparation is reduced, for example, by adding sulfur dioxide to the ketene gas.{{Cite patent | country = EP | number =0377438 | title = | gdate = 1990-06-11 | invent1 = R. Bergamin et al. | assign1 = Lonza AG}} Because of its cumulative double bonds, ethenone is highly reactive and reacts in an addition reaction H-acidic compounds to the corresponding acetic acid derivatives. It does for example react with water to acetic acid or with primary or secondary amines to the corresponding acetamides.

Ethenone is produced by thermal dehydration of acetic acid at 700–750 °C in the presence of triethyl phosphate as a catalyst:{{cite book |doi=10.1002/14356007.a15_063 |chapter=Ketenes |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2001 |last1=Miller |first1=Raimund |last2=Abaecherli |first2=Claudio |last3=Said |first3=Adel |last4=Jackson |first4=Barry |isbn=978-3-527-30385-4 }}{{citation | last = Arpe | first = Hans-Jürgen | title = Industrielle organische Chemie: Bedeutende vor- und Zwischenprodukte | url = https://books.google.com/books?id=36kHHvzx6M8C&q=wacker+verfahren+essigs%C3%A4ureanhydrid&pg=PA200 | edition = 6th | publisher = Wiley-VCH | location = Weinheim | pages = 200–201 | isbn = 978-3-527-31540-6 | year = 2007 | language = de}}{{Dead link|date=March 2024 |bot=InternetArchiveBot |fix-attempted=yes }}

:{{chem2|CH3CO2H -> CH2\dC\dO + H2O}}

It has also been produced on a laboratory scale by the thermolysis of acetone at {{nowrap|600–700 °C}}.{{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 }}{{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}}

:{{chem2|CH3COCH3 →CH2\dC\dO + CH4}}

This reaction is called the Schmidlin ketene synthesis.{{cite journal | first1 = Julius | last1 = Schmidlin | first2 = Maximilian | last2 = Bergman | name-list-style = 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 = de | journal = Berichte der Deutschen Chemischen Gesellschaft | volume = 43 | issue = 3| pages = 2821–2823 | doi=10.1002/cber.19100430340}}

On a laboratory scale it can be produced by the thermal decomposition of Meldrum's acid at temperatures greater than 200 °C.{{cn|date=January 2024}}

Ethenone was first produced in 1907 by N. T. M. Wilsmore through pyrolysis of acetone or acetic anhydride vapours over a hot platinum wire in an apparatus that was later developed by Charles D. Hurd into the "Hurd lamp" or "ketene lamp". This apparatus consists of a heated flask of acetone producing vapours which are pyrolyzed by a metal filament electrically heated to red heat, with a condenser to return unreacted acetone to the boiling flask. Other heating methods have been used and similar methods were used on a larger scale for the industrial production of ketene for acetic anhydride synthesis.{{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}}K.-H. Lautenschläger, W. Schröter, A. Wanninger, "Taschenbuch der Chemie", 20. Aufl. 2006, {{ISBN|978-3-8171-1761-1}}.{{OrgSynth|Kurzcode=cv1p0330|Autor=C.D. Hurd|title=Ketene|Jahrgang=1925|Volume=4|Seiten=39|ColVol=1|ColVolSeiten=330|doi=10.15227/orgsyn.004.0039}}

Ethenone was discovered at the same time by Hermann Staudinger (by reaction of bromoacetyl bromide with metallic zinc)H. Staudinger H. W. Klever (1908): "Keten. Bemerkung zur Abhandlung zur Abhandlung der HHrn. V.T. Wilsmore und A. W. Stewart". Berichte der deutschen chemischen Gesellschaft, volume 41, issue 1, pages 1516-1517. {{doi|10.1002/cber.190804101275}}Tidwell, T. T. (2005), "Ein Jahrhundert Ketene (1905–2005): die Entdeckung einer vielseitigen Klasse reaktiver Intermediate". Angewandte Chemie, volume 117, pages 5926–5933. {{doi|10.1002/ange.200500098}} The dehydration of acetic acid was reported in 1910.J. Schmidlin, M. Bergman (1910): Berichte der deutschen chemischen Gesellschaft, volume 43, pages 2821- {{doi|10.1002/cber.19100430340}}

File:Ethenone synthesis from bromoacetyl bromide.png

The thermal decomposition of acetic anhydride was also described.Norman Thomas Mortimer Wilsmore (1907): "Keten". Journal of the Chemical Society, Transactions, volume 91, article CLXXXVIII (188), pages 1938-1941. {{doi|10.1039/ct9079101938}}

File:Ethenone synthesis from acetic anhydride.png

File:Ethenone synthesis from acetone.png

File:Ethenone synthesis from acetic acid.png

Ethenone has been observed to occur in space, in comets or in gas as part of the interstellar medium.{{cite journal |last1=Hudson |first1=Reggie L. |last2=Loeffler |first2=Mark J. |title=Ketene Formation in Interstellar Ices: A Laboratory Study |journal=The Astrophysical Journal |date=31 July 2013 |volume=773 |issue=2 |pages=109 |doi=10.1088/0004-637x/773/2/109 |bibcode=2013ApJ...773..109H |hdl=2060/20140010162 |s2cid=37437108 |hdl-access=free }}

Ethenone is used to make acetic anhydride from acetic acid. Generally it is used for the acetylation of chemical compounds.

:File:Ketene reactions.png

:File:Mechanism-Ketene_Reactions_V1.svg

Ethenone reacts with formaldehyde in the presence of catalysts such as Lewis acids (AlCl₃, ZnCl₂ or BF₃) to give β-propiolactone.Hans-Jürgen Arpe, "Industrielle Organische Chemie", 6. Aufl., 2007, WILEY-VCH Verlag, Weinheim, {{ISBN|978-3-527-31540-6}}. The technically most significant use of ethenone is the synthesis of sorbic acid by reaction with crotonaldehyde in toluene at about 50 °C in the presence of zinc salts of long-chain carboxylic acids. This produces a polyester of 3-hydroxy-4-hexenoic acid, which is thermally{{Cite patent | country = EP | number =1295860 | title = | gdate = 26. März 2003-03-26 | invent1 = D. Decker et al.| assign1 = Nutrinova GmbH}} or hydrolytically depolymerized to sorbic acid.

Ethenone is very reactive, tending to react with nucleophiles to form an acetyl group. For example, it reacts with water to form acetic acid;Tidwell, [https://books.google.com/books?id=AdczJj26oG8C&pg=PA11 p. 11]. with acetic acid to form acetic anhydride; with ammonia and amines to form ethanamides;Tidwell, p. 560. and with dry hydrogen halides to form acetyl halides.ChemSpider http://www.chemspider.com/Chemical-Structure.9643.html

The formation of acetic acid likely occurs by an initial formation of 1,1-dihydroxyethene, which then tautomerizes to give the final product.{{cite journal |journal= Can. J. Chem. |volume= 77 |pages= 817–829 |year= 1999 |title= The hydration mechanism of ketene: 15 years later |first1= Minh Tho |last1= Nguyen |first2= Greet |last2= Raspoet |issue= 5–6 |doi= 10.1139/v99-090 }}

Ethenone will also react with itself via [2 + 2] photocycloadditions to form cyclic dimers known as diketenes. For this reason, it should not be stored for long periods.Christoph Taeschler :Ketenes, Ketene Dimers, and Related Substances, Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley & Sons, New York, 2010

Exposure to concentrated levels causes humans to experience irritation of body parts such as the eye, nose, throat and lungs. Extended toxicity testing on mice, rats, guinea pigs and rabbits showed that ten-minute exposures to concentrations of freshly generated ethenone as low as 0.2 mg/liter (116 ppm) may produce a high percentage of deaths in small animals. These findings show ethenone is toxicologically identical to phosgene.{{cite journal | title = The Inhalation Toxicity of Ketene and of Ketene Dimer |author1=H. A. Wooster |author2=C. C. Lushbaugh |author3=C. E. Redeman | journal = J. Am. Chem. Soc. | year = 1946 | volume = 68 | issue = 12 | pages = 2743 | doi = 10.1021/ja01216a526}}{{RömppOnline|Name=Diketen |Datum=16. Juni 2014 |ID=RD-04-01613 }}

The formation of ketene in the pyrolysis of vitamin E acetate, an additive of some e-liquid products, is one possible mechanism of the reported pulmonary damage{{Cite web|url=https://time.com/5753947/vaping-lung-disease-outbreak-peak/|title = The Vaping-Related Lung Disease Outbreak May be Coming to an End| date=20 December 2019 }} caused by electronic cigarette use.{{cite journal |last1=Wu |first1=Dan |last2=O’Shea |first2=Donal F. |title=Potential for release of pulmonary toxic ketene from vaping pyrolysis of vitamin E acetate |journal=Proceedings of the National Academy of Sciences |date=24 March 2020 |volume=117 |issue=12 |pages=6349–6355 |doi=10.1073/pnas.1920925117 |pmid=32156732 |pmc=7104367 |bibcode=2020PNAS..117.6349W |doi-access=free }}

A number of patents describe the catalytic formation of ketene from carboxylic acids and acetates, using a variety of metals or ceramics, some of which are known to occur in e-cigarette devices from patients with e-cigarette or vaping product-use associated lung injury (EVALI).{{cite journal |last1=Attfield |first1=Kathleen R. |last2=Chen |first2=Wenhao |last3=Cummings |first3=Kristin J. |last4=Jacob |first4=Peyton |last5=O’Shea |first5=Donal F. |last6=Wagner |first6=Jeff |last7=Wang |first7=Ping |last8=Fowles |first8=Jefferson |title=Potential of Ethenone (Ketene) to Contribute to Electronic Cigarette, or Vaping, Product Use–associated Lung Injury |journal=American Journal of Respiratory and Critical Care Medicine |date=15 October 2020 |volume=202 |issue=8 |pages=1187–1189 |doi=10.1164/rccm.202003-0654LE |pmid=32551843 |s2cid=219919028 |url=https://figshare.com/articles/journal_contribution/16997875 }}U.S. patent No. 5475144. Catalyst and process for synthesis of ketenes from carboxylic acids. Dec 12, 1995. https://patents.google.com/patent/US5475144A/en

Occupational exposure limits are set at 0.5 ppm (0.9 mg/m³) over an eight-hour time-weighted average.{{cite web

| last = Centers for Disease Control and Prevention

| author-link = Centers for Disease Control and Prevention

| title = Ketene

| work = NIOSH Pocket Guide to Chemical Hazards

| publisher =

| date = 4 April 2013

| url = https://www.cdc.gov/niosh/npg/npgd0367.html

| doi =

| accessdate = 13 November 2013}}

An IDLH limit is set at 5 ppm, as this is the lowest concentration productive of a clinically relevant physiologic response in humans.{{cite web

| last = Centers for Disease Control and Prevention

| author-link = Centers for Disease Control and Prevention

| title = Ketene

| work = Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs)

| publisher =

| date = May 1994

| url = https://www.cdc.gov/niosh/idlh/463514.html

| doi =

| accessdate = 13 November 2013}}

{{Reflist}}

• Tidwell, Thomas T. [http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0471692824.html Ketenes], 2nd edition. John Wiley & Sons, 2006, {{ISBN|978-0-471-69282-9}}.

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Category:Ketenes

Category:Gases

Category:Pulmonary agents

Category:Acetylating agents