Carbonyl bromide

Carbonyl bromide[1]

Structural formula of carbonyl bromide Ball-and-stick model of carbonyl bromide
Names
Preferred IUPAC name Carbonyl dibromide
Other names Bromophosgene, carbonic dibromide
Identifiers
CAS Number	593-95-3^Y
3D model (JSmol)	Interactive image
ChemSpider	71389^Y
PubChem CID	79057
UNII	MNU12QTS1I^Y
CompTox Dashboard (EPA)	DTXSID20208041
InChI InChI=1S/CBr2O/c2-1(3)4^Y Key: MOIPGXQKZSZOQX-UHFFFAOYSA-N^Y InChI=1/CBr2O/c2-1(3)4 Key: MOIPGXQKZSZOQX-UHFFFAOYAM
SMILES BrC(Br)=O
Properties
Chemical formula	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
Solubility in water	reacts
Thermochemistry
Heat capacity (C)	61.8 J/(mol·K) (gas)
Std molar entropy (S^⦵298)	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)	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). Y verify (what is ^YN ?) Infobox references

Carbonyl bromide, also known as bromophosgene, is a carbon oxohalide and a bromine analogue of phosgene, with the chemical formula COBr₂. It is a colorless liquid. Carbonyl bromide is a decomposition product of halon compounds used in fire extinguishers.[2]

Synthesis and reactions

Carbonyl bromide is formed by the oxidation of 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 Δ_RH < 0 and Δ_RS < 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 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