Carbonyl bromide

Carbonyl bromide, also known as bromophosgene, is an organic chemical compound with the chemical formula COBr2. 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]

Carbonyl bromide[1]
Structural formula of carbonyl bromide
Structural formula of carbonyl bromide
Ball-and-stick model of carbonyl bromide
Ball-and-stick model of carbonyl bromide
Names
Preferred IUPAC name
Carbonyl dibromide
Other names
Bromophosgene, carbonic dibromide
Identifiers
3D model (JSmol)
ChemSpider
UNII
  • InChI=1S/CBr2O/c2-1(3)4 checkY
    Key: MOIPGXQKZSZOQX-UHFFFAOYSA-N checkY
  • InChI=1/CBr2O/c2-1(3)4
    Key: MOIPGXQKZSZOQX-UHFFFAOYAM
  • BrC(Br)=O
Properties
COBr2
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
61.8 J/(mol·K) (gas)
309.1 J/(mol·K) (gas)
−127.2 or −145.2 kJ/mol (liquid)
−96.2 or −114 kJ/mol (gas)
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
4
0
1
Related compounds
Related compounds
 Carbonyl fluoride
Phosgene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Synthesis and reactions

Carbonyl bromide is formed by the oxidation carbon tetrabromide with sulfuric acid:

CBr4 + H2SO4 → COBr2 + SO2 + Br2 + H2O

In contrast to phosgene, carbonyl bromide cannot be produced efficiently by halogenation of carbon monoxide. The bromination of carbon monoxide follows this equation:

CO + Br2 ⇌ COBr2

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]

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
  1. 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
  2. US Occupational Safety and Health Administration (May 1996). "Common Fire Extinguishing Agents". Archived from the original on 2009-09-12. Retrieved 2009-11-21.
  3. T.A. Ryan; E.A. Seddon; K.R. Seddon; C. Ryan (24 May 1996). Phosgene: And Related Carbonyl Halides. pp. 669–671. ISBN 9780080538808. Retrieved April 11, 2015.
  4. 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.
  5. Katrizsky, Alan R.; Meth-Cohn, Otto; Wees, Charles W. (1995), Organic Functional Group Transformations, vol. 6, Elsevier, pp. 417–8, ISBN 978-0-08-042704-1, retrieved 2009-11-23
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