Dibromine monoxide

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Dibromine monoxide
IUPAC name Oxygen dibromide[note 1]
Other names Bromine(I) oxide
Hypobromous anhydride
Dibromooxidane
Dibromidooxygen
Identifiers
InChI InChI=1/Br2O/c1-3-2
InChIKey HJCMMOODWZOXML-UHFFFAOYAD
Standard InChI InChI=1S/Br2O/c1-3-2
Standard InChIKey HJCMMOODWZOXML-UHFFFAOYSA-N
CAS number [21308-80-5]
ChemSpider 10686917
Properties[3][4]
Chemical formula Br2O
Molar mass 175.81 g mol−1
Appearance dark brown solid
Density 4.10 g cm−3 (crystal)
Melting point

−17.5 °C (255.7 K) decomp.

Structure[4]
Space group Pc21n (No. 33)
Lattice constant a = 390.4(1) pm, b = 686.2(1) pm, c = 1062.2(2) pm
Thermochemistry[5]
Std enthalpy of formation ΔfHo298 +107.1(35) kJ mol−1
Related compounds
Other cations Difluorine monoxide
Dichlorine monoxide
Other oxides of bromine Bromine dioxide
Other compounds Hypobromous acid
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Dibromine monoxide, Br2O, is a binary compound of bromine and oxygen. The dark brown solid is unstable at room temperature.[3][6] It is prepared by the reaction of bromine with mercury(II) oxide[7][8] or by the low temperature decomposition of bromine dioxide in vacuo.[9][10] Other routes include the photolysis of mixtures of oxygen and bromine vapour[11][12] and the reaction of BrOTeF5 with water.[4]

Structure

Dibromine monoxide has a bent C2v structure in the vapour phase, as expected from VSEPR theory, with r(Br–O) = 184.29(20) pm, θ(Br–O–Br) = 112.24(20)°.[12] In the solid state, the symmetry is lower, with slightly different Br–O distances (185.7(5), 187.5(5) pm) and θ(Br–O–Br) = 114.2(2)°.[4] Solid Br2O has also been studied by infrared spectroscopy[11][13][14][15] and by EXAFS.[15]

Reactivity

Dibromine monoxide is a strong oxidizing agent, converting iodine to diiodine pentoxide and benzene to 1,4-benzoquinone.[3] It is formally the anhydride of hypobromous acid, and gives the hypobromite ion BrO− in alkaline solution.[3]

Notes and references

Notes

  1. ↑ Although oxygen is more electronegative than bromine on the normal numerical scales,[1] it appears after the halogens on the conventional electronegativity series used in inorganic nomenclature.[2] Hence, OBr2 is considered a bromide of oxygen, and not an oxide of bromine, for nomenclature purposes.

References

  1. ↑ Allred, A. L. Electronegativity values from thermochemical data. J. Inorg. Nucl. Chem. 1961, 17 (3–4), 215–21. DOI: 10.1016/0022-1902(61)80142-5.
  2. ↑ Nomenclature of Inorganic Chemistry; IUPAC Recommendations 2005; Royal Society of Chemistry: Cambridge, 2005; p 260. ISBN 0-85404-438-8, <http://www.iupac.org/publications/books/rbook/Red_Book_2005.pdf>.
  3. ↑ 3.0 3.1 3.2 3.3 Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 996–97. ISBN 0-08-022057-6.
  4. ↑ 4.0 4.1 4.2 4.3 Hwang, In-Chur; Kuschel, Raimund; Seppelt, Konrad Structures of Bromine Oxygen Compounds. Z. Anorg. Allg. Chem., 623 (1–6), 379–83. DOI: 10.1002/zaac.19976230160.
  5. ↑ Thorn, R. Peyton, Jr.; Monks, Paul S.; Stief, Louis J.; Kuo, Szu-Cherng; Zhang, Zhengyu; Klemm, R. Bruce Photoionization Efficiency Spectrum, Ionization Energy, and Heat of Formation of Br2O. J. Phys. Chem. 1996, 100 (30), 12199–203. DOI: 10.1021/jp960405z.
  6. ↑ Cotton, F. Albert; Wilkinson, Geoffrey Advanced Inorganic Chemistry, 5th ed.; Wiley-Interscience: New York, 1988; p 562. ISBN 0-471-84997-9.
  7. ↑ Zintl, E.; Rienäcker, G. Über die Existenz eines flüchtigen Bromoxyds. Ber. Dtsch. Chem. Ges. B 1930, 63 (5), 1098–1104. DOI: 10.1002/cber.19300630516.
  8. ↑ Brenschede, W.; Schumacher, H.-J. Über die Darstellung und einige Eigenschaften eines Bromoxyds von der Formel Br2O. Z. Anorg. Allg. Chem. 1936, 226 (4), 370–84. DOI: 10.1002/zaac.19362260409.
  9. ↑ Schwarz, R.; Wiele, H. Über das Bromoxyd Br2O. Naturwissenschaften 1938, 26 (45), 742. DOI: 10.1007/BF01774152.
  10. ↑ Schwarz, Robert; Wiele, Heinz Zur Kenntnis der Bromoxyde (II. Mitteilung). J. Prakt. Chem. 1938, 152 (3–6), 157–76. DOI: 10.1002/prac.19391520306.
  11. ↑ 11.0 11.1 Campbell, C.; Jones, J. P. M.; Turner, J. J. Spectroscopic studies of bromine oxides: the infrared spectrum of solid bromide monoxide. Chem. Commun. (London) 1968 (15), 888–89. DOI: 10.1039/C19680000888.
  12. ↑ 12.0 12.1 Müller, Holger S. P.; Cohen, Edward A. Dibromine monoxide, Br2O: The rotational spectrum and molecular properties. J. Chem. Phys. 1997, 106 (20), 8344–54. DOI: 10.1063/1.473920.
  13. ↑ Tevault, D.; Walker, N.; Smardzewski, R.; Fox, W. Infrared spectra of the BrO and OBrO free radicals and of BrOBr and BrBrO molecules in Solid Argon at 10K. J. Phys. Chem. 1978, 82 (25), 2733–36. DOI: 10.1021/j100514a022.
  14. ↑ Allen, S. D.; Poliakoff, M.; Turner, J. J. Photochemistry of an ozone-bromine complex; the IR spectrum of matrix isolated Br2O. J. Mol. Struct. 1987, 157 (1–3), 1–15. DOI: 10.1016/0022-2860(87)87078-3.
  15. ↑ 15.0 15.1 Levason, William; Ogden, J. Steven; Spicer, Mark D.; Young, Nigel A. Characterization of dibromine monoxide (Br2O) by bromine K-edge EXAFS and IR spectroscopy. J. Am. Chem. Soc. 1990, 112 (3), 1019–22. DOI: 10.1021/ja00159a019.

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