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Xenon tetroxide

Names
IUPAC names Xenon tetraoxide Xenon(VIII) oxide
Other names Xenon tetroxide Perxenic anhydride
Identifiers
CAS Number	12340-14-6
3D model (JSmol)	Interactive image
ChemSpider	21106492
CompTox Dashboard (EPA)	DTXSID40893695
InChI InChI=1S/O4Xe/c1-5(2,3)4Key: VHWKDFQUJRCZDZ-UHFFFAOYSA-N InChI=1/O4Xe/c1-5(2,3)4Key: VHWKDFQUJRCZDZ-UHFFFAOYAS
SMILES O=(=O)(=O)=O
Properties
Chemical formula	XeO4
Molar mass	195.29 g mol
Appearance	Yellow solid below −36 °C
Melting point	−35.9 °C (−32.6 °F; 237.2 K)
Boiling point	0 °C (32 °F; 273 K)
Solubility in water	reacts
Structure
Molecular shape	Tetrahedral
Dipole moment	0 D
Thermochemistry
Std enthalpy of formation (ΔfH298)	+153.5 kcal mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	powerful explosive
Related compounds
Related compounds	Perxenic acid Xenon trioxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). N verify (what is  ?) Infobox references

Xenon tetroxide is a chemical compound of xenon and oxygen with molecular formula XeO₄, remarkable for being a relatively stable compound of a noble gas. It is a yellow crystalline solid that is stable below −35.9 °C; above that temperature it is very prone to exploding and decomposing into elemental xenon and oxygen (O₂).

All eight valence electrons of xenon are involved in the bonds with the oxygen, and the oxidation state of the xenon atom is +8. Oxygen is the only element that can bring xenon up to its highest oxidation state; even fluorine can only give XeF₆ (+6).

Two other short-lived xenon compounds with an oxidation state of +8, XeO₃F₂ and XeO₂F₄, are accessible by the reaction of xenon tetroxide with xenon hexafluoride. XeO₃F₂ and XeO₂F₄ can be detected with mass spectrometry. The perxenates are also compounds where xenon has the +8 oxidation state.

Reactions

At temperatures above −35.9 °C, xenon tetroxide is very prone to explosion, decomposing into xenon and oxygen gases with ΔH = −643 kJ/mol:

XeO₄ → Xe + 2 O₂

Xenon tetroxide dissolves in water to form perxenic acid and in alkalis to form perxenate salts:

XeO₄ + 2 H₂O → H₄XeO₆

XeO₄ + 4 NaOH → Na₄XeO₆ + 2 H₂O

Xenon tetroxide can also react with xenon hexafluoride to give xenon oxyfluorides:

XeO₄ + XeF₆ → XeOF₄ + XeO₃F₂

XeO₄ + 2XeF₆ → XeO₂F₄ + 2 XeOF₄

Synthesis

All syntheses start from the perxenates, which are accessible from the xenates through two methods. One is the disproportionation of xenates to perxenates and xenon:

2 HXeO
₄ + 2 OH → XeO
₆ + Xe + O₂ + 2 H₂O

The other is oxidation of the xenates with ozone in basic solution:

HXeO
₄ + O₃ + 3 OH → XeO
₆ + O₂ + 2 H₂O

Barium perxenate is reacted with sulfuric acid and the unstable perxenic acid is dehydrated to give xenon tetroxide:

Ba
₂XeO
₆ + 2 H
₂SO
₄ → 2 BaSO
₄ + H
₄XeO
₆

H
₄XeO
₆ → 2 H
₂O + XeO
₄

Any excess perxenic acid slowly undergoes a decomposition reaction to xenic acid and oxygen:

2 H
₄XeO
₆ → O
₂ + 2 H
₂XeO
₄ + 2 H
₂O

References

1. Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, Florida: CRC Press. p. 494. ISBN 0-8493-0594-2.
2. G. Gundersen; K. Hedberg; J. L.Huston (1970). "Molecular Structure of Xenon Tetroxide, XeO₄". J. Chem. Phys. 52 (2): 812–815. Bibcode:1970JChPh..52..812G. doi:10.1063/1.1673060.
3. Gunn, S. R. (May 1965). "The Heat of Formation of Xenon Tetroxide". Journal of the American Chemical Society. 87 (10): 2290–2291. doi:10.1021/ja01088a038.
4. H.Selig, J. G. Malm, H. H. Claassen, C. L. Chernick, J. L. Huston (1964). "Xenon tetroxide – Preparation & Some Properties". Science. 143 (3612): 1322–3. Bibcode:1964Sci...143.1322S. doi:10.1126/science.143.3612.1322. JSTOR 1713238. PMID 17799234. S2CID 29205117.{{cite journal}}: CS1 maint: multiple names: authors list (link)
5. J. L. Huston; M. H. Studier; E. N. Sloth (1964). "Xenon tetroxide — Mass Spectrum". Science. 143 (3611): 1162–3. Bibcode:1964Sci...143.1161H. doi:10.1126/science.143.3611.1161-a. JSTOR 1712675. PMID 17833897. S2CID 28547895.
6. A. Earnshaw; Norman Greenwood (1997). Chemistry of the Elements (2nd ed.). Elsevier. p. 901. ISBN 9780080501093.

• Lide, D. R., ed. (2002). CRC Handbook of Chemistry and Physics (83rd ed.). Boca Raton, Florida: CRC Press. ISBN 0-8493-0483-0.

• Xenon(VIII) compounds
• Inorganic compounds
• Oxides