Chlorine monoxide

Chlorine monoxide is a chemical radical with the chemical formula ClO. It plays an important role in the process of ozone depletion. In the stratosphere, chlorine atoms react with ozone molecules to form chlorine monoxide and oxygen.

Cl· + O
3 → ClO· + O
2
This article is about the compound ClO. For the oxoanion with the formula ClO−
, see hypochlorite. For the molecule Cl2O, see Dichlorine monoxide.
Chlorine monoxide
Names
Preferred IUPAC name
Chlorine monoxide
Systematic IUPAC name
Chlorooxidanyl
Other names
Chlorine(II) oxide
Identifiers
3D model (JSmol)
Abbreviations ClO(.)
ChEBI
ChemSpider
MeSH Chlorosyl
UNII
Properties
ClO
Molar mass 51.45 g·mol−1
Thermochemistry
Std enthalpy of
formation (ΔfH⦵298)
 101.8 kJ/mol[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

This reaction causes the depletion of the ozone layer.[1] This result ClO· radicals can further react as such:

ClO· + O· → Cl· + O
2

regenerating the chlorine radical. In this way, the overall reaction for the decomposition of ozone is catalyzed by chlorine, as ultimately chlorine remains unchanged. The overall reaction is:

O· + O
3 → + 2O
2

This has been a significant impact of the use of CFCs on the upper stratosphere, however many countries have agreed to ban the use of CFCs. The nonreactive nature of CFC's allows them to pass into the stratosphere, where they undergo photo-dissociation to form Cl radicals. These then readily form chlorine monoxide, and this cycle can continue until two radicals react to form dichlorine monoxide, terminating the radical reaction. Because the concentration of CFCs in atmosphere is very low, the probability of a terminating reaction is exceedingly low, meaning each radical can decompose many thousands of molecules of ozone.

Even though the use of CFCs was banned in many countries, CFCs can stay in the atmosphere for about 50-500 years. This cause many chlorine radicals to be produced and hence a significant amount of ozone molecules are decomposed before the chlorine radicals are able to react with chlorine monoxide to form Dichlorine monoxide.

References
  1. Egon Wiberg; Nils Wiberg; Arnold Frederick Holleman (2001). Inorganic chemistry. Academic Press. p. 462. ISBN 0-12-352651-5.
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