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| Names | |
|---|---|
| IUPAC name Dichlorine heptoxide | |
| Other names Chlorine(VII) oxide; Perchloric anhydride; (Perchloryloxy)chlorane trioxide | |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChemSpider |
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| UNII | |
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| Properties | |
| Cl2O7 | |
| Molar mass | 182.901 g/mol |
| Appearance | colorless liquid, colorless gas |
| Density | 1.9 g/cm3 |
| Melting point | −91.57 °C (−132.83 °F; 181.58 K) |
| Boiling point | 82.07 °C (179.73 °F; 355.22 K) |
| hydrolyzes to formperchloric acid | |
| Thermochemistry | |
Std enthalpy of formation(ΔfH⦵298) | 275.7 kJ/mol |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | oxidizer, contact explosive[1] |
| NFPA 704 (fire diamond) | |
| Related compounds | |
Related compounds | Manganese heptoxide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Dichlorine heptoxide is thechemical compound with theformulaCl2O7. Thischlorine oxide is theanhydride ofperchloric acid. It is produced by the careful distillation of perchloric acid in the presence of the dehydrating agentphosphorus pentoxide:[1]
Cl2O7 can be distilled off from the mixture.
It may also be formed by illumination of mixtures of chlorine andozone with blue light.[2] It slowlyhydrolyzes back toperchloric acid.
Cl2O7 is anendergonic molecule, meaning it is intrinsically unstable, decomposing to its constituent elements with release of energy:[3]
Dichlorine heptoxide is a covalent compound consisting of twoClO3 groups linked by an oxygen atom. It has an overallbent molecular geometry (C2symmetry), with a Cl−O−Cl angle of 118.6°. The chlorine–oxygenbond lengths are 1.709 Å in the central region and 1.405 Å within eachClO3 cluster.[1] In this compound, chlorine exists in its highest formaloxidation state of +7.
Dichlorine heptoxide reacts with primary and secondaryamines incarbon tetrachloride solution to yield perchloric amides:[4]
It also reacts withalkenes to give alkyl perchlorates. For example, it reacts withpropene in carbon tetrachloride solution to yield isopropyl perchlorate and 1-chloro-2-propyl perchlorate.[5]
Dichlorine heptoxide reacts withalcohols to form alkyl perchlorates.[6]
Dichlorine heptoxide is a strongly acidic oxide, and in solution it forms an equilibrium with perchloric acid.
Although it is the most stable chlorine oxide,Cl2O7 is a strong oxidizer as well as an explosive that can be set off with flame or mechanical shock, or by contact withiodine.[7] Nevertheless, it is less strongly oxidising than the other chlorine oxides, and does not attacksulfur,phosphorus, orpaper when cold.[1] It has the same effects on the human body as elementalchlorine, and requires the same precautions.[8]
