Dichlorine monoxide

Source: Wikipedia, the free encyclopedia.
Not to be confused with chlorine monoxide.
Dichlorine monoxide
Structure of dichlorine monoxide; Cl-O bond length is 170.0 pm, bond angle is 110.9°.
Space-filling model of dichlorine monoxide
Names
Other names
Oxygen dichloride
Oxygen chloride
Dichlorine oxide
Chlorine (I) oxide
Hypochlorous oxide
Hypochlorous anhydride
Identifiers
3D model (
JSmol
)
ChEBI
ChemSpider
ECHA InfoCard
 100.029.312 Edit this at Wikidata
UNII
  • InChI=1S/Cl2O/c1-3-2 checkY
    Key: RCJVRSBWZCNNQT-UHFFFAOYSA-N checkY
  • InChI=1/Cl2O/c1-3-2
    Key: RCJVRSBWZCNNQT-UHFFFAOYAA
  • ClOCl
Properties
Cl2O
Molar mass 86.9054 g/mol
Appearance brownish-yellow gas
Melting point −120.6 °C (−185.1 °F; 152.6 K)
Boiling point 2.0 °C (35.6 °F; 275.1 K)
very soluble, hydrolyses 143 g Cl2O per 100 g water
Solubility in other solvents soluble in CCl4
Structure
0.78 ± 0.08 D
Thermochemistry
265.9 J K−1 mol−1
Std enthalpy of
formation
(ΔfH⦵298)
 +80.3 kJ mol−1
Hazards
GHS labelling:
GHS05: Corrosive GHS09: Environmental hazard
Danger
H290, H314, H400, H411
P234, P260, P264, P273, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P311, P321, P363, P390, P391, P405, P406, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneInstability 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
4
3
OX
Safety data sheet (SDS) [1]
Related compounds
Other cations
  • Diiodine monoxide
Related compounds
 Oxygen difluoride, nitrous oxide, chlorine dioxide
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 monoxide is an

Gay-Lussac also determined its composition. In older literature it is often referred to as chlorine monoxide,[3] which can be a source of confusion as that name now refers to the ClO• radical
.

At room temperature it exists as a brownish-yellow gas which is soluble in both water and organic solvents. Chemically, it is a member of the

anhydride of hypochlorous acid
. It is a strong oxidiser and chlorinating agent.

Preparation

The earliest method of synthesis was to treat mercury(II) oxide with chlorine gas.[3] However, this method is expensive, as well as highly dangerous due to the risk of mercury poisoning.

2 Cl2 + HgO →
HgCl2
+ Cl2O

A safer and more convenient method of production is the reaction of chlorine gas with hydrated sodium carbonate at 20–30 °C.[3]

2 Cl2 + 2 Na2CO3 + H2O → Cl2O + 2
NaHCO3
+ 2 NaCl
2 Cl2 + 2
NaHCO3
→ Cl2O + 2 CO2 + 2 NaCl + H2O

This reaction can be performed in the absence of water but requires heating to 150–250 °C; as dichlorine monoxide is unstable at these temperatures[4] it must therefore be continuously removed to prevent thermal decomposition.

2 Cl2 + Na2CO3 → Cl2O + CO2 + 2 NaCl

Structure

The structure of dichlorine monoxide is similar to that of water and

steric repulsion
between the bulky chlorine atoms.

In the solid state, it crystallises in the tetrahedral space group I41/amd, making it isostructural to the high pressure form of water, ice VIII.[5]

Reactions

Dichlorine monoxide is highly soluble in water,

CCl4,[3] but the equilibrium constant ultimately favours the formation of hypochlorous acid.[7]

2 HOCl ⇌ Cl2O + H2O K (0 °C) = 3.55x10−3 dm3/mol

Despite this, it has been suggested that dichlorine monoxide may be the active species in the reactions of

olefins and aromatic compounds,[8][9] as well as in the chlorination of drinking water.[10]

With inorganic compounds

Dichlorine monoxide reacts with

oxyhalides.[11][12][3]

VOCl3
+ Cl2O → VO2Cl + 2 Cl2
TiCl4
+ Cl2O → TiOCl2 + 2 Cl2
SbCl5
+ 2 Cl2O → SbO2Cl + 4 Cl2

Similar reactions have also been observed with certain inorganic halides.[13][14]

AsCl3
+ 2 Cl2O → AsO2Cl + 3 Cl2
NO2Cl
+ Cl2

With organic compounds

Dichlorine monoxide is an effective chlorinating agent. It can be used for either the side-chain or ring chlorination of deactivated

olefins and aromatic compounds.[8][9]

Photochemistry

Dichlorine monoxide undergoes photodissociation, eventually forming O2 and Cl2. The process is primarily radical based, with flash photolysis showing radical hypochlorite (ClO·) to be a key intermediate.[17]

2 Cl2O → 2 Cl2 + O2

Explosive properties

Dichlorine monoxide is explosive, although there is a lack of modern research into this behaviour.

minimum explosive limit. There are conflicting reports of it exploding on exposure to strong light.[19][20] Heating above 120 °C, or a rapid rate of heating at lower temperatures also apparently lead to explosions.[3]
Liquid dichlorine monoxide has been reported to be shock-sensitive.[21]

References

  1. ^ "CHLORINE MONOXIDE". CAMEO Chemicals. National Oceanic and Atmospheric Administration. Retrieved 12 May 2015.
  2. ^ Balard, A.J. (1834). "Recherches sur la nature des combinaisons décolorantes du chlore" [Investigations into the nature of bleaching compounds of chlorine]. Annales de Chimie et de Physique. 2nd series (in French). 57: 225–304.
  3. ^
    doi:10.1021/cr60302a004
    .
  4. doi:10.1039/CT9232302730
    .
  5. doi:10.1524/zkri.1998.213.4.237
    .
  6. doi:10.1021/ie50389a021
    .
  7. ISBN 9780123526519.{{cite book}}: CS1 maint: multiple names: authors list (link
    )
  8. ^
    doi:10.1021/ja00764a050
    .
  9. ^
    PMID 20302364
    .
  10. PMID 20302368
    .
  11. doi:10.1002/zaac.19673510302
    .
  12. doi:10.1002/zaac.19613090505
    .
  13. doi:10.1002/cber.19640971215
    .
  14. doi:10.1002/anie.196600781
    .
  15. doi:10.1021/ja00381a032
    .
  16. PMID 22211432
    .
  17. S2CID 98084403
    .
  18. doi:10.1021/ja01225a501
    .
  19. doi:10.1021/ja01283a504
    .
  20. doi:10.1039/TF9312700648
    .
  21. ISSN 0020-1669
    .
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