Ethenone

Source: Wikipedia, the free encyclopedia.
Ethenone
Structural formula
Space-filling model
Names
Preferred IUPAC name
Ethenone[1]
Other names
Ketene
Carbomethene
Keto-ethylene
Identifiers
3D model (
JSmol
)
1098282
ChEBI
ChemSpider
ECHA InfoCard
 100.006.671 Edit this at Wikidata
EC Number
  • 207-336-9
RTECS number
  • OA7700000
UNII
  • InChI=1S/C2H2O/c1-2-3/h1H2 checkY
    Key: CCGKOQOJPYTBIH-UHFFFAOYSA-N checkY
  • 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
C2H2O
Molar mass 42.037 g/mol
Appearance Colourless 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
ethyl ether
aromatic solvents
halocarbons
Vapor pressure >1 atm (20°C)[2]
1.4355
Thermochemistry
51.75 J/K mol
Std enthalpy of
formation
(ΔfH⦵298)
 -87.24 kJ/mol
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 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).
☒N verify (what is checkY☒N ?)

In organic chemistry, 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]

Properties

Ethenone is a highly reactive gas (at

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:[6][7]

CH3CO2H → CH2=C=O + H2O

It has also been produced on a laboratory scale by the thermolysis of acetone at 600–700 °C.[8][9]

CH3COCH3 →CH2=C=O + CH4

This reaction is called the Schmidlin ketene synthesis.[10]

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

When passed through heated pipes or electrically heated metal (like copper) wires at 500-600 °C in the presence of carbon disulfide, acetone decomposes into methane and ethenone, with 95% yield.[11][12] Ethenone was discovered at the same time by Hermann Staudinger (by reaction of bromoacetyl bromide with metallic zinc)[13][14] The dehydration of acetic acid was reported in 1910.[15]

The thermal decomposition of acetic anhydride was also described.[16]

Natural occurrence

Ethenone has been observed to occur in space, in comets or in gas as part of the interstellar medium.[17]

Use

Ethenone is used to make acetic anhydride from acetic acid. Generally it is used for the acetylation of chemical compounds.[18]

Reactions with ammonia, water, ethanol, and acetic acid
Reactions with ammonia, water, ethanol, and acetic acid
Mechanism of the above reactions
Mechanism of the above reactions

Ethenone reacts 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[20]
or hydrolytically depolymerized to sorbic acid.

Ethenone is very reactive, tending to react with

hydrogen halides to form acetyl halides.[23]

The formation of acetic acid likely occurs by an initial formation of

tautomerizes to give the final product.[24]

Ethenone will also react with itself via

dimers known as diketenes. For this reason, it should not be stored for long periods.[25]

Hazards

Exposure to concentrated levels causes humans to experience irritation of body parts such as the

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.[26][18]

The formation of ketene in the

e-liquid products, is one possible mechanism of the reported pulmonary damage[27] caused by electronic cigarette use.[28]
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).[29][30]

Occupational exposure limits are set at 0.5 ppm (0.9 mg/m3) over an eight-hour time-weighted average.[31] An

IDLH limit is set at 5 ppm, as this is the lowest concentration productive of a clinically relevant physiologic response in humans.[32]

References

  1. ISBN 978-0-85404-182-4
    .
  2. ^ a b c d NIOSH Pocket Guide to Chemical Hazards. "#0367". National Institute for Occupational Safety and Health (NIOSH).
  3. ^ a b "Ketene". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. ISBN 978-3527306732
    .
  5. ^ EP 0377438, R. Bergamin et al., issued 1990-06-11, assigned to Lonza AG 
  6. ISBN 978-3-527-30385-4
    .
  7. ISBN 978-3-527-31540-6[permanent dead link
    ]
  8. ISBN 978-0471937494
    .
  9. ^ Hurd CD, Kamm O (1941). "Ketene in Organic Syntheses". Organic Syntheses. Vol. Collective Vol. 1. p. 330.
  10. doi:10.1002/cber.19100430340
    .
  11. ISBN 978-3-8171-1761-1
    .
  12. doi:10.15227/orgsyn.004.0039
    .
  13. doi:10.1002/cber.190804101275
  14. doi:10.1002/ange.200500098
  15. doi:10.1002/cber.19100430340
    .
  16. doi:10.1039/ct9079101938
  17. S2CID 37437108
    .
  18. ^ a b Entry on Diketen. at: Römpp Online. Georg Thieme Verlag, retrieved 16. Juni 2014.
  19. ISBN 978-3-527-31540-6
    .
  20. ^ EP 1295860, D. Decker et al., issued 26. März 2003-03-26, assigned to Nutrinova GmbH 
  21. ^ Tidwell, p. 11.
  22. ^ Tidwell, p. 560.
  23. ^ ChemSpider http://www.chemspider.com/Chemical-Structure.9643.html
  24. doi:10.1139/v99-090
    .
  25. ^ Christoph Taeschler :Ketenes, Ketene Dimers, and Related Substances, Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley & Sons, New York, 2010
  26. doi:10.1021/ja01216a526
    .
  27. ^ "The Vaping-Related Lung Disease Outbreak May be Coming to an End". 20 December 2019.
  28. PMID 32156732
    .
  29. S2CID 219919028
    .
  30. ^ 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
  31. ^ Centers for Disease Control and Prevention (4 April 2013). "Ketene". NIOSH Pocket Guide to Chemical Hazards. Retrieved 13 November 2013.
  32. ^ Centers for Disease Control and Prevention (May 1994). "Ketene". Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs). Retrieved 13 November 2013.

Literature

External links

  • Media related to Ethenone at Wikimedia Commons
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