Chlorine perchlorate
Dichlorine tetraoxide.svg
Chlorine perchlorate molecule spacefill.png
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]

2 ClO2 → 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):

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


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][5]


  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. ^ So far, all attempts to form iodine perchlorate (IOClO3) have failed, because the iodine atom oxidizes to +3 oxidation state immediately.[citation needed]


  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. ^ Gomberg, M. (1923-02-01). "The Reaction Between Silver Perchlorate and Iodine. Chlorine Tetra-Oxide". Journal of the American Chemical Society. 45 (2): 398–421. doi:10.1021/ja01655a017. ISSN 0002-7863.
HClO4 He
LiClO4 Be(ClO4)2 B(ClO4)4
ROClO3 N(ClO4)3
H3OClO4 FClO4 Ne
NaClO4 Mg(ClO4)2 Al(ClO4)3
Si P S ClO4
KClO4 Ca(ClO4)2 Sc(ClO4)3 Ti(ClO4)4 VO(ClO4)3
Cr(ClO4)3 Mn(ClO4)2 Fe(ClO4)2 Co(ClO4)2,
Ni(ClO4)2 Cu(ClO4)2 Zn(ClO4)2 Ga(ClO4)3 Ge As Se Br Kr
RbClO4 Sr(ClO4)2 Y(ClO4)3 Zr(ClO4)4 Nb(ClO4)5 Mo Tc Ru Rh(ClO4)3 Pd(ClO4)2 AgClO4 Cd(ClO4)2 In(ClO4)3 Sn(ClO4)4 Sb TeO(ClO4)2 I Xe
CsClO4 Ba(ClO4)2   Lu(ClO4)3 Hf(ClO4)4 Ta(ClO4)5 W Re Os Ir Pt Au Hg2(ClO4)2,
Pb(ClO4)2 Bi(ClO4)3 Po At Rn
FrClO4 Ra   Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
La Ce(ClO4)x Pr(ClO4)3 Nd(ClO4)3 Pm Sm(ClO4)3 Eu(ClO4)3 Gd(ClO4)3 Tb(ClO4)3 Dy(ClO4)3 Ho(ClO4)3 Er(ClO4)3 Tm(ClO4)3 Yb(ClO4)3
Ac Th(ClO4)4 Pa UO2(ClO4)2 Np Pu Am Cm Bk Cf Es Fm Md No