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{{chembox
{{chembox
| Watchedfields = changed
| Watchedfields = changed
| verifiedrevid = 449829633
| verifiedrevid = 449829633
| ImageFile = Dichlorine heptoxide.svg
| ImageFile = Dichlorine heptoxide.svg
| ImageSize = 180
| ImageSize = 180
| ImageFile1 = Dichlorine-heptoxide-3D-balls.png
| ImageFile1 = Dichlorine-heptoxide-3D-balls.png
| ImageSize1 = 180
| ImageSize1 = 180
| IUPACName = Dichlorine heptoxide
| IUPACName = Dichlorine heptoxide
| OtherNames = Chlorine(VII) oxide; Perchloric anhydride; (Perchloryloxy)chlorane trioxide
| OtherNames = Chlorine(VII) oxide; Perchloric anhydride; (Perchloryloxy)chlorane trioxide
|Section1={{Chembox Identifiers
| Section1 = {{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 109884
| ChemSpiderID = 109884
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| SMILES = O=Cl(=O)(=O)OCl(=O)(=O)=O
| SMILES = O=Cl(=O)(=O)OCl(=O)(=O)=O
}}
}}
|Section2={{Chembox Properties
| Section2 = {{Chembox Properties
| Formula = Cl<sub>2</sub>O<sub>7</sub>
| Formula = Cl<sub>2</sub>O<sub>7</sub>
| MolarMass = 182.901 g/mol
| MolarMass = 182.901 g/mol
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| Solubility = hydrolyzes to form [[perchloric acid]]
| Solubility = hydrolyzes to form [[perchloric acid]]
}}
}}
| Section3={{Chembox Thermochemistry
| Section3 = {{Chembox Thermochemistry
| DeltaHf = 275.7{{nbsp}}kJ/mol
| DeltaHf = 275.7{{nbsp}}kJ/mol
}}
}}
|Section4={{Chembox Hazards
| Section4 = {{Chembox Hazards
| GHSPictograms = {{GHS03}} {{GHS05}} {{GHS06}} {{GHS08}} {{GHS09}}
| GHSPictograms = {{GHS01}} {{GHS03}} {{GHS05}} {{GHS06}} {{GHS08}} {{GHS09}}
| NFPA-H = 3
| NFPA-H = 3
| NFPA-F = 0
| NFPA-F = 0
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| AutoignitionPt =
| AutoignitionPt =
}}
}}
|Section5={{Chembox Related
| Section5 = {{Chembox Related
| OtherCompounds = [[Manganese heptoxide]]
| OtherCompounds = [[Manganese heptoxide]]
}}
}}

Revision as of 06:30, 1 October 2024

Dichlorine heptoxide
Names
IUPAC name
Dichlorine heptoxide
Other names
Chlorine(VII) oxide; Perchloric anhydride; (Perchloryloxy)chlorane trioxide
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
UNII
  • InChI=1S/Cl2O7/c3-1(4,5)9-2(6,7)8 checkY
    Key: SCDFUIZLRPEIIH-UHFFFAOYSA-N checkY
  • InChI=1.001/Cl2O7/c3-1(4,5)9-2(6,7)8
    Key: SCDFUIZLRPEIIH-UHFFFAOYAG
  • O=Cl(=O)(=O)OCl(=O)(=O)=O
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 form perchloric acid
Thermochemistry
275.7 kJ/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 oxidizer, contact explosive[1]
GHS labelling:
GHS01: Explosive GHS03: Oxidizing GHS05: Corrosive GHS06: Toxic GHS08: Health hazard GHS09: Environmental hazard
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g. hydrogen peroxideSpecial hazard OX: Oxidizer. E.g. potassium perchlorate
3
0
3
OX
Related compounds
Related compounds
 Manganese heptoxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Dichlorine heptoxide is the chemical compound with the formula Cl2O7. This chlorine oxide is the anhydride of perchloric acid. It is produced by the careful distillation of perchloric acid in the presence of the dehydrating agent phosphorus pentoxide:[1]

2 HClO4 + P4O10 → Cl2O7 + H2P4O11

The chlorine(VII) oxide can be distilled off from the mixture.

It may also be formed by illumination of mixtures of chlorine and ozone with blue light.[2] It slowly hydrolyzes back to perchloric acid.

Structure

Cl2O7 is an endergonic molecule, meaning it is intrinsically unstable, decomposing to its constituent elements with release of energy:[3]

2 Cl2O7 → 2 Cl2 + 7 O2 (ΔH° = –132 kcal/mol)

Dichlorine heptoxide is a covalent compound consisting of two ClO3 portions linked by an oxygen atom. It has an overall bent molecular geometry (C2 symmetry), with a Cl−O−Cl angle of 118.6°. The chlorine–oxygen bond lengths are 1.709 Å in the central region and 1.405 Å within each ClO3 cluster.[1] In this compound, chlorine exists in its highest formal oxidation state of +7.

Chemistry

Dichlorine heptoxide reacts with primary and secondary amines in carbon tetrachloride solution to yield perchloric amides:[4]

2 RNH
2 + Cl
2O
7 → 2 RNHClO
3 + H
2O
2 R
2NH + Cl
2O
7 → 2 R
2NClO
3 + H
2O

It also reacts with alkenes to give alkyl perchlorates. For example, it reacts with propene in carbon tetrachloride solution to yield isopropyl perchlorate and 1-chloro-2-propyl perchlorate.[5]

Dichlorine heptoxide reacts with alcohols to form alkyl perchlorates.[6]

Dichlorine heptoxide is a strongly acidic oxide, and in solution it forms an equilibrium with perchloric acid.

Safety

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 with iodine.[7] Nevertheless, it is less strongly oxidising than the other chlorine oxides, and does not attack sulfur, phosphorus, or paper when cold.[1] It has the same effects on the human body as elemental chlorine, and requires the same precautions.[8]

References

  1. ^ a b c d Holleman, Arnold F.; Wiberg, Egon (2001). Inorganic chemistry. Translated by Mary Eagleson; William Brewer. San Diego: Academic Press. p. 464. ISBN 0-12-352651-5.
  2. ^ Byrns, A. C.; Rollefson, G. K. (1934). "The Formation of Chlorine Heptoxide on Illumination of Mixtures of Chlorine and Ozone". Journal of the American Chemical Society. 56 (5): 1250–1251. doi:10.1021/ja01320a506.
  3. ^ Martin, Jan M. L (2006-10-12). "Heats of formation of perchloric acid, HClO4, and perchloric anhydride, Cl2O7. Probing the limits of W1 and W2 theory". Journal of Molecular Structure: THEOCHEM. Modelling Structure and Reactivity: the 7th triennial conference of the World Association of Theoritical and Computational Chemists (WATOC 2005). 771 (1): 19–26. arXiv:physics/0508076. doi:10.1016/j.theochem.2006.03.035. ISSN 0166-1280. S2CID 98385268.
  4. ^ Beard, C. D.; Baum, K. (1974). "Reactions of dichlorine heptoxide with amines". Journal of the American Chemical Society. 96 (10): 3237–3239. doi:10.1021/ja00817a034.
  5. ^ Baum, K. . (1976). "Reactions of dichlorine heptoxide with olefins". The Journal of Organic Chemistry. 41 (9): 1663–1665. doi:10.1021/jo00871a048.
  6. ^ Baum, Kurt; Beard, Charles D. (1974-05-01). "Reactions of dichlorine heptoxide with alcohols". Journal of the American Chemical Society. 96 (10): 3233–3237. doi:10.1021/ja00817a033. ISSN 0002-7863.
  7. ^ Lewis, Robert Alan (1998). Lewis' dictionary of toxicology. CRC Press. p. 260. ISBN 1-56670-223-2.
  8. ^ Jeanne Mager Stellman, ed. (1998). "Halogens and their compounds". Encyclopaedia of occupational health and safety (4th ed.). International Labour Organization. p. 104.210. ISBN 92-2-109817-6.
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