Dichlorine heptoxide

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Dichlorine heptoxide
IUPAC name
Dichlorine heptoxide
Other names
Chlorine heptoxide
Chlorine(VII) oxide
Perchloric anhydride
(Perchloryloxy)chlorane trioxide
Jmol-3D images Image
Molar mass 182.901 g/mol
Appearance Colorless liquid
Odor Odorless
Density 1.811 g/cm3 (20 °C)[1]
Melting point −91.57 °C (−132.83 °F; 181.58 K)
Boiling point 82 °C (180 °F; 355 K)
Hydrolyzes to form perchloric acid
Solubility Reacts with organic solvents
Miscible with carbon tetrachloride
Soluble in benzene, phosphoryl chloride
Vapor pressure 72 mmHg (20 °C)
251 kJ/mol
Safety data sheet None
Flash point Non-flammable
Related compounds
Related compounds
Chlorine dioxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Dichlorine heptoxide is a chemical compound, a clear, oily liquid. It is a strong oxidizing agent. The compound has the chemical formula Cl2O7.



Dichlorine heptoxide reacts exothermically with water to yield perchloric acid.

Dichlorine heptoxide reacts with primary and secondary amines in carbon tetrachloride solution to yield perchloric amides:

2 RNH2 + Cl2O7 → 2 RNHClO3 + H2O
2 R2NH + Cl2O7 → 2 R2NClO3 + H2O

Unlike other chlorine oxides, dichlorine heptoxide does not attack sulfur, phosphorus, or paper at standard conditions.


Dichlorine heptoxide is a clear, oily, very volatile liquid. It reacts with water and organic compounds, but dissolves in halocarbons.


Dichlorine heptoxide is not available due to its hazards, but can be made in situ.


This preparation is extremely dangerous because of the explosive and very oxidizing nature of Cl2O7.

Dichlorine heptoxide can be obtained by dehydrating perchloric acid with phosphorus pentoxide.

12 HClO4 + P4O10 → 4 H3PO4 + 6 Cl2O7

The reaction has to be performed under 0 °C, optimally between -70 °C to -10 °C. The resulting product has to be distilled very carefully under vacuum to safely obtain pure dichlorine heptoxide.

Other routes involve oxidizing chlorine or chlorine oxides with ozone, under UV light.


  • Make pure perchloric acid



Dichlorine heptoxide is explosive and a strong oxidizer, that can be set off in contact with flame or mechanical shock, or in presence of iodine. It is very corrosive and toxic in contact with skin, mouth or eyes.


Best to use it as quickly as possible.


Dichlorine heptoxide can be safely neutralized by slowly adding it in cold water or ice, followed by neutralization with a base.


  1. Rosolovskii, V. Ya.; Zinov'ev, A. A.; Prokhorov, V. A.; Zhurnal Neorganicheskoi Khimii; vol. 5; (1960); p. 334 - 335; Zhurnal Neorganicheskoi Khimii; vol. 5; (1960); p. 692 - 694

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