Ethenone
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| Names | |
|---|---|
| Preferred IUPAC name
Ethenone | |
| Other names
Ketene Carbomethene Keto-ethylene | |
| Identifiers | |
| 3D model (JSmol) |
|
| 1098282 | |
| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.006.671 |
| EC Number | 207-336-9 |
| PubChem CID |
|
| RTECS number | OA7700000 |
| |
| |
| 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 acetone ethanol ethyl ether aromatic solvents halocarbons |
| Vapor pressure | >1 atm (20°C)[1] |
| Refractive index (nD) |
1.4355 |
| Thermochemistry | |
| 51.75 J/K mol | |
| Std enthalpy of formation (ΔfH |
-87.24 kJ/mol |
| Hazards | |
| Safety data sheet | External MSDS |
| NFPA 704 | |
| Flash point | −107 °C (−161 °F; 166 K) |
| Explosive limits | 5.5-18% |
| Lethal dose or concentration (LD, LC): | |
| LD50 (median dose) |
1300 mg/kg (oral, rat) |
| LC50 (median concentration) |
17 ppm (mouse, 10 min)[2] |
| LCLo (lowest published) |
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)[2] |
| US health exposure limits (NIOSH): | |
| PEL (Permissible) |
TWA 0.5 ppm (0.9 mg/m3)[1] |
| REL (Recommended) |
TWA 0.5 ppm (0.9 mg/m3) ST 1.5 ppm (3 mg/m3)[1] |
| IDLH (Immediate danger) |
5 ppm[1] |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
 verify (what is  ?) | |
| Infobox references | |
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 a tautomer of ethynol.
Properties
Ethenone is a very poisonous colourless gas at STP and has a sharp irritating odour. It is soluble in acetone, ethanol, ethyl ether, aromatic solvents and halocarbons.
Preparation
Ethenone can be prepared in the laboratory by pyrolysis of acetone vapor.[3] It is also formed by reacting acetyl chloride with a proton acceptor like trimethylamine.
Reactions
Ethenone is very reactive, tending to react with nucleophiles to form an acetyl group. For example, it reacts with water to form acetic acid;[4] with acetic acid to form acetic anhydride; with ammonia and amines to form ethanamides;[5] and with dry hydrogen halides to form acetyl halides.[6]
Ethenone will also react with itself via 2+2 photocycloaddition to form cyclic dimers known as diketenes. For this reason, it should not be stored for long periods.[7]
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 put ethenone in the same order of toxicity as phosgene (0.2–20 mg/liter) and hydrogen cyanide (0.2-0.5 mg/liter). Death is from pulmonary edema and is entirely similar to, but much more rapid than is the case with phosgene poisoning.[8]
Occupational exposure limits are set at 0.5 ppm (0.9 mg/m3) over an eight-hour time-weighted average.[9] An IDLH limit is set at 5 ppm, as this is the lowest concentration productive of a clinically relevant physiologic response in humans.[10]
References
- 1 2 3 4 "NIOSH Pocket Guide to Chemical Hazards #0367". National Institute for Occupational Safety and Health (NIOSH).
- 1 2 "Ketene". Immediately Dangerous to Life and Health. National Institute for Occupational Safety and Health (NIOSH).
- ↑ C. D. Hurd (1941). "Ketene". Org. Synth.; Coll. Vol., 1, p. 330.
- ↑ Tidwell, p. 11.
- ↑ Tidwell, p. 560.
- ↑ ChemSpider http://www.chemspider.com/Chemical-Structure.9643.html
- ↑ Christoph Taeschler :Ketenes, Ketene Dimers, and Related Substances, Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley & Sons, New York, 2010
- ↑ 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.
- ↑ Centers for Disease Control and Prevention (4 April 2013). "Ketene". NIOSH Pocket Guide to Chemical Hazards. Retrieved 13 November 2013.
- ↑ Centers for Disease Control and Prevention (May 1994). "Ketene". Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs). Retrieved 13 November 2013.