Ethenone

Last updated
Ethenone
Structural formula of ethenone.svg
Ketene-3D-vdW.png
Names
Preferred IUPAC name
Ethenone [1]
Other names
Ketene
Carbomethene
Keto-ethylene
Identifiers
3D model (JSmol)
1098282
ChEBI
ChemSpider
ECHA InfoCard 100.006.671 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 207-336-9
PubChem CID
RTECS number
  • OA7700000
UNII
  • InChI=1S/C2H2O/c1-2-3/h1H2 Yes check.svgY
    Key: CCGKOQOJPYTBIH-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C2H2O/c1-2-3/h1H2
    Key: CCGKOQOJPYTBIH-UHFFFAOYSA-N
  • InChI=1/C2H2O/c1-2-3/h1H2
    Key: CCGKOQOJPYTBIH-UHFFFAOYAO
  • O=C=C
Properties
C2 H2 O
Molar mass 42.037 g/mol
AppearanceColourless gas
Odor penetrating
Density 1.93 g/cm3
Melting point −150.5 °C (−238.9 °F; 122.6 K)
Boiling point −56.1 °C (−69.0 °F; 217.1 K)
decomposes
Solubility soluble in acetone
ethanol
ethyl ether
aromatic solvents
halocarbons
Vapor pressure >1 atm (20°C) [2]
1.4355
Thermochemistry
51.75 J/K mol
-87.24 kJ/mol
Hazards
NFPA 704 (fire diamond)
NFPA 704.svgHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
4
4
1
Flash point −107 °C (−161 °F; 166 K)
Explosive limits 5.5-18%
Lethal dose or concentration (LD, LC):
1300 mg/kg (oral, rat)
17 ppm (mouse, 10 min) [3]
23 ppm (mouse, 30 min)
53 ppm (rabbit, 2 hr)
53 ppm (guinea pig, 2 hr)
750 ppm (cat, 10 min)
200 ppm (monkey, 10 min)
50 ppm (mouse, 10 min)
1000 ppm (rabbit, 10 min) [3]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 0.5 ppm (0.9 mg/m3) [2]
REL (Recommended)
TWA 0.5 ppm (0.9 mg/m3) ST 1.5 ppm (3 mg/m3) [2]
IDLH (Immediate danger)
5 ppm [2]
Safety data sheet (SDS) External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Ethenone is the formal name for ketene, an organic compound with formula C2H2O or H2C=C=O. It is the simplest member of the ketene class. It is an important reagent for acetylations. [4] [5]

Contents

Properties

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. [6] 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.

Preparation

Ethenone is produced by thermal dehydration of acetic acid at 700–750 °C in the presence of triethyl phosphate as a catalyst: [7] [8]

CH3CO2H → CH2=C=O + H2O

It has also been produced on a laboratory scale by the thermolysis of acetone at 600–700 °C. [9] [10]

CH3COCH3 →CH2=C=O + CH4

This reaction is called the Schmidlin ketene synthesis. [11]

On a laboratory scale it can be produced by the thermal decomposition of Meldrum's acid at temperatures greater than 200 °C.[ citation needed ]

History

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. [12] [13] [14]

Ethenone was discovered at the same time by Hermann Staudinger (by reaction of bromoacetyl bromide with metallic zinc) [15] [16] The dehydration of acetic acid was reported in 1910. [17]

Ethenone synthesis from bromoacetyl bromide.png

The thermal decomposition of acetic anhydride was also described. [18]

Ethenone synthesis from acetic anhydride.png
Ethenone synthesis from acetone.png
Ethenone synthesis from acetic acid.png

Natural occurrence

Ethenone has been observed to occur in space, in comets or in gas as part of the interstellar medium. [19]

Use

Ethenone is used to make acetic anhydride from acetic acid. Generally it is used for the acetylation of chemical compounds. [20]

Reactions with ammonia, water, ethanol, and acetic acid Ketene reactions.png
Reactions with ammonia, water, ethanol, and acetic acid
Mechanism of the above reactions Mechanism-Ketene Reactions V1.svg
Mechanism of the above reactions

Ethenone reacts with methanal in the presence of catalysts such as Lewis acids (AlCl3, ZnCl2 or BF3) to give β-propiolactone. [21] The technically most significant use of ethenone is the synthesis of sorbic acid by reaction with 2-butenal (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 [22] 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; [23] with acetic acid to form acetic anhydride; with ammonia and amines to form ethanamides; [24] and with dry hydrogen halides to form acetyl halides. [25]

The formation of acetic acid likely occurs by an initial formation of 1,1-dihydroxyethene, which then tautomerizes to give the final product. [26]

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. [27]

Hazards

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. [28] [20]

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 [29] caused by electronic cigarette use. [30] 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). [31] [32]

Occupational exposure limits are set at 0.5 ppm (0.9 mg/m3) over an eight-hour time-weighted average. [33] An IDLH limit is set at 5 ppm, as this is the lowest concentration productive of a clinically relevant physiologic response in humans. [34]

Related Research Articles

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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. The name may also refer to the specific compound ethenone H2C=C=O, the simplest ketene.

<span class="mw-page-title-main">Diels–Alder reaction</span> Chemical reaction

In organic chemistry, the Diels–Alder reaction is a chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene derivative. It is the prototypical example of a pericyclic reaction with a concerted mechanism. More specifically, it is classified as a thermally allowed [4+2] cycloaddition with Woodward–Hoffmann symbol [π4s + π2s]. It was first described by Otto Diels and Kurt Alder in 1928. For the discovery of this reaction, they were awarded the Nobel Prize in Chemistry in 1950. Through the simultaneous construction of two new carbon–carbon bonds, the Diels–Alder reaction provides a reliable way to form six-membered rings with good control over the regio- and stereochemical outcomes. Consequently, it has served as a powerful and widely applied tool for the introduction of chemical complexity in the synthesis of natural products and new materials. The underlying concept has also been applied to π-systems involving heteroatoms, such as carbonyls and imines, which furnish the corresponding heterocycles; this variant is known as the hetero-Diels–Alder reaction. The reaction has also been generalized to other ring sizes, although none of these generalizations have matched the formation of six-membered rings in terms of scope or versatility. Because of the negative values of ΔH° and ΔS° for a typical Diels–Alder reaction, the microscopic reverse of a Diels–Alder reaction becomes favorable at high temperatures, although this is of synthetic importance for only a limited range of Diels–Alder adducts, generally with some special structural features; this reverse reaction is known as the retro-Diels–Alder reaction.

<span class="mw-page-title-main">Dimethylaniline</span> Chemical compound

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<span class="mw-page-title-main">Phthalic anhydride</span> Chemical compound

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<span class="mw-page-title-main">Resorcinol</span> Chemical compound

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<span class="mw-page-title-main">Methyl acetate</span> Chemical compound

Methyl acetate, also known as MeOAc, acetic acid methyl ester or methyl ethanoate, is a carboxylate ester with the formula CH3COOCH3. It is a flammable liquid with a characteristically pleasant smell reminiscent of some glues and nail polish removers. Methyl acetate is occasionally used as a solvent, being weakly polar and lipophilic, but its close relative ethyl acetate is a more common solvent being less toxic and less soluble in water. Methyl acetate has a solubility of 25% in water at room temperature. At elevated temperature its solubility in water is much higher. Methyl acetate is not stable in the presence of strong aqueous bases or aqueous acids. Methyl acetate is not considered a VOC in the USA.

<span class="mw-page-title-main">Acetic anhydride</span> Organic compound with formula (CH₃CO)₂O

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<span class="mw-page-title-main">Meldrum's acid</span> Chemical compound

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References

  1. ↑ "Front Matter". Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 723. doi:10.1039/9781849733069-FP001. ISBN   978-0-85404-182-4.
  2. 1 2 3 4 NIOSH Pocket Guide to Chemical Hazards. "#0367". National Institute for Occupational Safety and Health (NIOSH).
  3. 1 2 "Ketene". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. ↑ Miller, Raimund; Abaecherli, Claudio; Said, Adel; Jackson, Barry (2001). "Ketenes". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a15_063. ISBN   3527306730.
  5. ↑ Mitzel, Thomas M.; Pigza, Julie A. (2009). "Ketene". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rk000.pub2. ISBN   978-0-471-93623-7.
  6. ↑ EP 0377438,R. Bergamin et al.,issued 1990-06-11, assigned to Lonza AG
  7. ↑ Miller, Raimund; Abaecherli, Claudio; Said, Adel; Jackson, Barry (2001). "Ketenes". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a15_063. ISBN   978-3-527-30385-4.
  8. ↑ Arpe, Hans-Jürgen (2007), Industrielle organische Chemie: Bedeutende vor- und Zwischenprodukte (in German) (6th ed.), Weinheim: Wiley-VCH, pp. 200–201, ISBN   978-3-527-31540-6 [ permanent dead link ]
  9. ↑ Weygand C (1972). Hilgetag G, Martini A (eds.). Weygand/Hilgetag Preparative Organic Chemistry (4th ed.). New York: John Wiley & Sons, Inc. pp. 1031–1032. ISBN   978-0471937494.
  10. ↑ Hurd CD, Kamm O (1941). "Ketene in Organic Syntheses". Organic Syntheses. Vol. Collective Vol. 1. p. 330.
  11. ↑ Schmidlin J, Bergman M (1910). "Darstellung des Ketens aus Aceton" [Preparation of ketene from acetone]. Berichte der Deutschen Chemischen Gesellschaft (in German). 43 (3): 2821–2823. doi:10.1002/cber.19100430340.
  12. ↑ 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.
  13. ↑ K.-H. Lautenschläger, W. Schröter, A. Wanninger, "Taschenbuch der Chemie", 20. Aufl. 2006, ISBN   978-3-8171-1761-1.
  14. ↑ "Ketene". Organic Syntheses . doi:10.15227/orgsyn.004.0039 .
  15. ↑ 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
  16. ↑ 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
  17. ↑ J. Schmidlin, M. Bergman (1910): Berichte der deutschen chemischen Gesellschaft, volume 43, pages 2821- doi : 10.1002/cber.19100430340
  18. ↑ Norman Thomas Mortimer Wilsmore (1907): "Keten". Journal of the Chemical Society, Transactions, volume 91, article CLXXXVIII (188), pages 1938-1941. doi : 10.1039/ct9079101938
  19. ↑ Hudson, Reggie L.; Loeffler, Mark J. (31 July 2013). "Ketene Formation in Interstellar Ices: A Laboratory Study". The Astrophysical Journal. 773 (2): 109. Bibcode:2013ApJ...773..109H. doi:10.1088/0004-637x/773/2/109. hdl: 2060/20140010162 . S2CID   37437108.
  20. 1 2 Entry on Diketen . at: Römpp Online . Georg Thieme Verlag, retrieved 16. Juni 2014.
  21. ↑ Hans-Jürgen Arpe, "Industrielle Organische Chemie", 6. Aufl., 2007, WILEY-VCH Verlag, Weinheim, ISBN   978-3-527-31540-6.
  22. ↑ EP 1295860,D. Decker et al.,issued 26. März 2003-03-26, assigned to Nutrinova GmbH
  23. ↑ Tidwell, p. 11.
  24. ↑ Tidwell, p. 560.
  25. ↑ ChemSpider http://www.chemspider.com/Chemical-Structure.9643.html
  26. ↑ Nguyen, Minh Tho; Raspoet, Greet (1999). "The hydration mechanism of ketene: 15 years later". Can. J. Chem. 77 (5–6): 817–829. doi:10.1139/v99-090.
  27. ↑ Christoph Taeschler :Ketenes, Ketene Dimers, and Related Substances, Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley & Sons, New York, 2010
  28. ↑ H. A. Wooster; C. C. Lushbaugh; C. E. Redeman (1946). "The Inhalation Toxicity of Ketene and of Ketene Dimer". J. Am. Chem. Soc. 68 (12): 2743. doi:10.1021/ja01216a526.
  29. ↑ "The Vaping-Related Lung Disease Outbreak May be Coming to an End". 20 December 2019.
  30. ↑ Wu, Dan; O’Shea, Donal F. (24 March 2020). "Potential for release of pulmonary toxic ketene from vaping pyrolysis of vitamin E acetate". Proceedings of the National Academy of Sciences. 117 (12): 6349–6355. Bibcode:2020PNAS..117.6349W. doi: 10.1073/pnas.1920925117 . PMC   7104367 . PMID   32156732.
  31. ↑ Attfield, Kathleen R.; Chen, Wenhao; Cummings, Kristin J.; Jacob, Peyton; O’Shea, Donal F.; Wagner, Jeff; Wang, Ping; Fowles, Jefferson (15 October 2020). "Potential of Ethenone (Ketene) to Contribute to Electronic Cigarette, or Vaping, Product Use–associated Lung Injury". American Journal of Respiratory and Critical Care Medicine. 202 (8): 1187–1189. doi:10.1164/rccm.202003-0654LE. PMID   32551843. S2CID   219919028.
  32. ↑ 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
  33. ↑ Centers for Disease Control and Prevention (4 April 2013). "Ketene". NIOSH Pocket Guide to Chemical Hazards. Retrieved 13 November 2013.
  34. ↑ Centers for Disease Control and Prevention (May 1994). "Ketene". Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs). Retrieved 13 November 2013.

Literature

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