Chlorine perchlorate
IUPAC name
Chloro perchlorate[1]
Systematic IUPAC name
Chloro perchlorate[1]
Other names
Chlorine(I,VII) oxide
Dichlorine tetroxide
3D model (JSmol)
  • InChI=1S/Cl2O4/c1-6-2(3,4)5 ☒N
  • ClO[Cl](=O)(=O)=O
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)
Occupational safety and health (OHS/OSH):
Main hazards
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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 ClOClO3. It is produced by the photodimerization of chlorine dioxide (ClO2) at room temperature by 436 nm ultraviolet light:[2][3][4]

2ClO2 → ClOClO3

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

CsClO4 + ClOSO2F → Cs(SO3)F + ClOClO3


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):

2ClOClO3 → O2 + Cl2 + Cl2O6

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

CrO2Cl2 + 2ClOClO3 → 2Cl2 + CrO2(ClO4)2
TiCl4 + 4ClOClO3 → 4Cl2 + Ti(ClO4)4
2AgCl + 2 ClOClO3 → 2AgClO4 + Cl2


Reactant Conditions Products
Heat dichlorine hexoxide (80%), chlorine dioxide, chlorine, oxygen
Ultraviolet light dichlorine heptoxide, chlorine, oxygen[4]
caesium iodide −45 °C Cs[I(OClO3)4][note 1]
ClOSO2F or ClF MClO4(M = Cs or NO2)[note 2]
bromine −45 °C bromine perchlorate (BrOClO3)[note 2]
iodine(0.33 mol) −50 °C I(OClO3)3[note 3]


  1. ^ Cs[I(OClO3)4] is a pale yellow salt which is stable at room temperature. It has a square IO4 unit.
  2. ^ a b MClO4 (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[5] attempt to form iodine monoperchlorate (IOClO3) occurred in 1972,[6] and even at low temperatures yielded instead the triperchlorate. On warming, the latter then decomposes to iodate.


  1. ^ a b "Chloro Perchlorate - PubChem Public Chemical Database". The PubChem Project. USA: National Center for Biotechnology Information.
  2. ^ A. J. Schell-Sorokin; D. S. Bethune; J. R. Lankard; M. M. T. Loy; P. P. Sorokin (1982). "Chlorine perchlorate a major photolysis product of chlorine dioxide". J. Phys. Chem. 86 (24): 4653–4655. doi:10.1021/j100221a001.
  3. ^ M. I. Lopez; J. E. Sicre (1988). "Ultraviolet spectrum of chlorine perchlorate". J. Phys. Chem. 92 (2): 563–564. doi:10.1021/j100313a062.
  4. ^ a b Rao, Balaji; Anderson, Todd A.; Redder, Aaron; Jackson, W. Andrew (2010-04-15). "Perchlorate Formation by Ozone Oxidation of Aqueous Chlorine/Oxy-Chlorine Species: Role of ClxOy Radicals". Environmental Science & Technology. 44 (8): 2961–2967. Bibcode:2010EnST...44.2961R. doi:10.1021/es903065f. ISSN 0013-936X. PMID 20345093.
  5. ^ Zefirov, N. S.; Zedankin, V. V.; Koz'min, A. S. (1988). "The synthesis and properties of covalent organic perchlorates". Russian Chemical Reviews. 57 (11). Turpion: 1047. doi:10.1070/RC1988v057n11ABEH003410. Translated from Uspekhi Khimii volume 57 (1988), pp. 1815-1839.
  6. ^ Christe, Karl O.; Schack, Carl J. (1972) [20 September 1971]. "Iodine tris­(perch1orate) and cesium tetrakis­(perchlorato)­iodate(III)". Inorganic Chemistry. 11 (7): 1684. doi:10.1021/ic50113a047.