Chemistry:Carbonyl bromide
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| Names | |||
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| Preferred IUPAC name
Carbonyl dibromide | |||
| Other names
Bromophosgene, carbonic dibromide
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| Identifiers | |||
3D model (JSmol)
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| Properties | |||
| COBr 2 | |||
| Molar mass | 187.818 g·mol−1 | ||
| Appearance | colorless liquid | ||
| Density | 2.52 g/mL at 15 °C | ||
| Boiling point | 64.5 °C (148.1 °F; 337.6 K) decomposes | ||
| reacts | |||
| Thermochemistry | |||
Heat capacity (C)
|
61.8 J/(mol·K) (gas) | ||
Std molar
entropy (S |
309.1 J/(mol·K) (gas) | ||
Std enthalpy of
formation (ΔfH⦵298) |
−127.2 or −145.2 kJ/mol (liquid) −96.2 or −114 kJ/mol (gas) | ||
| Hazards | |||
| NFPA 704 (fire diamond) | |||
| Related compounds | |||
Related compounds
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Carbonyl fluoride Phosgene | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
 verify (what is   ?)
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| Infobox references | |||
Carbonyl bromide, also known as bromophosgene, is an organic chemical compound with the chemical formula COBr
2. It is a colorless liquid. It is a bromine analogue of phosgene. It is a carbon oxohalide. Carbonyl bromide is a decomposition product of halon compounds used in fire extinguishers.[2]
Synthesis and reactions
Carbonyl bromide is formed by the oxidation carbon tetrabromide with sulfuric acid:
- CBr
4 + H
2SO
4 → COBr
2 + SO
2 + Br
2 + H
2O
In contrast to phosgene, carbonyl bromide cannot be produced efficiently by halogenation of carbon monoxide. The bromination of carbon monoxide follows this equation:
- CO + Br
2 ⇌ COBr
2
But the process is slow at room temperature. Increasing temperature, in order to increase the reaction rate, results in a further shift of the chemical equilibrium towards the educts (since ΔRH < 0 and ΔRS < 0).[3][4][clarification needed]
Carbonyl bromide slowly decomposes to carbon monoxide and elemental bromine even at low temperatures.[5] It is also sensitive to hydrolysis, breaking down into hydrogen bromide, water and carbon dioxide.
References
- ↑ Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, FL: CRC Press, pp. 3-96, 4-50, 5-26, ISBN 0-8493-0594-2
- ↑ US Occupational Safety and Health Administration (May 1996). "Common Fire Extinguishing Agents". http://www.osha.gov/doc/outreachtraining/htmlfiles/extagent.html.
- ↑ T.A. Ryan; E.A. Seddon; K.R. Seddon; C. Ryan (24 May 1996). Phosgene: And Related Carbonyl Halides. pp. 669–671. ISBN 9780080538808. https://books.google.com/books?id=fM43Ny2eFS8C&q=carbonyl+bromide+enthalpy+of+formation&pg=PA900. Retrieved April 11, 2015.
- ↑ Parkington, Michael J.; Ryan, T. Anthony; Seddon, Kenneth R. (1997). "Carbonyl dibromide: A novel reagent for the synthesis of metal bromides and bromide oxides". Journal of the Chemical Society, Dalton Transactions (2): 257–262. doi:10.1039/A603977D.
- ↑ Katrizsky, Alan R.; Meth-Cohn, Otto; Wees, Charles W. (1995), Organic Functional Group Transformations, 6, Elsevier, pp. 417–8, ISBN 978-0-08-042704-1, https://books.google.com/books?id=YzBveZGm0GEC&pg=PA417, retrieved 2009-11-23
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