Chlorine perchlorate

Chlorine perchlorate is a chemical compound with the formula Cl₂O₄. This chlorine oxide is an asymmetric oxide, with one chlorine atom in +1 oxidation state and the other +7, with proper formula Cl−O−ClO₃. It is produced by the photodimerization of chlorine dioxide (ClO₂) at room temperature by 436 nm ultraviolet light:^[3][4][5]

2 ClO₂ → ClOClO₃

Chlorine perchlorate

Names
IUPAC name Chloro perchlorate[1]
Systematic IUPAC name Chloro perchlorate[1]
Other names Chlorine(I,VII) oxide Dichlorine tetroxide (Chlorooxy)chlorane trioxide[2]
Identifiers
CAS Number	27218-16-2 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:52353
ChemSpider	147540 N
PubChem CID	168667
CompTox Dashboard (EPA)	DTXSID00181686
InChI InChI=1S/Cl2O4/c1-6-2(3,4)5 N Key: JRONPIZRZBBOBR-UHFFFAOYSA-N N
SMILES ClO[Cl](=O)(=O)=O
Properties
Chemical formula	Cl2O4
Molar mass	134.90 g·mol−1
Appearance	Pale green liquid
Density	1.81 g·cm−3
Melting point	−117 °C (−179 °F; 156 K)
Boiling point	20 °C (68 °F; 293 K) (decomposes)
Solubility in water	Reacts
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	oxidizer
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Chlorine perchlorate can also be made by the following reaction at −45 °C.

CsClO₄ + ClOSO₂F → CsSO₃F + ClOClO₃

Properties

Chlorine perchlorate is a pale greenish liquid. It is less stable than ClO₂ (chlorine dioxide)^{[citation needed]} and decomposes at room temperature to give O₂ (oxygen), Cl₂ (chlorine) and Cl₂O₆ (dichlorine hexoxide):

2 ClOClO₃ → O₂ + Cl₂ + Cl₂O₆

Chlorine perchlorate reacts with metal chlorides to form chlorine and the corresponding anhydrous perchlorate:

CrO₂Cl₂ + 2 ClOClO₃ → 2 Cl₂ + CrO₂(ClO₄)₂

TiCl₄ + 4 ClOClO₃ → 4 Cl₂ + Ti(ClO₄)₄

2 AgCl + 2 ClOClO₃ → 2 AgClO₄ + Cl₂

Reactions

Reactant	Conditions	Products
—	Heat	dichlorine hexoxide (80%), chlorine dioxide, chlorine, oxygen
—	Ultraviolet light	dichlorine heptoxide, chlorine, oxygen[5]
caesium iodide	−45 °C	caesium tetraperchloratoiodate(III) Cs+[I(OClO3)4]−[note 1]
ClOSO2F or ClF	—	M+ClO−4 (M = Cs or [NO2])[note 2]
bromine	−45 °C	bromine perchlorate (BrOClO3)[note 2]
iodine(0.33 mol)	−50 °C	iodine(III) perchlorate I(OClO3)3[note 3]

Notes

1. Cs⁺[I(OClO₃)₄]⁻ is a pale yellow salt which is stable at room temperature. It has a square IO₄ unit.
2. M⁺ClO−4 (M = Cs or [NO₂]) reacts with BrOSO₂F at −20 °C and produces bromine perchlorate (BrOClO₃). Bromine perchlorate then reacts with hydrogen bromide (HBr) at −70 °C and produces elemental bromine (Br₂) and perchloric acid (HClO₄).
3. The last^[6] attempt to form iodine monoperchlorate (IOClO₃) occurred in 1972,^[7] and even at low temperatures yielded instead the triperchlorate. On warming, the latter then decomposes to iodate.