Chlorine Monoxide
Definition and meaning of Chlorine Monoxide in chemistry.
Chlorine monoxide (ClO) is a highly reactive free radical formed when atomic chlorine reacts with ozone, and it serves as the key intermediate in catalytic cycles that destroy stratospheric ozone.
In more detail
ClO is generated by the reaction Cl + O3 → ClO + O2, and in the ozone-poor lower stratosphere it can react with atomic oxygen (ClO + O → Cl + O2) to regenerate free chlorine, sustaining a catalytic cycle that consumes ozone without the chlorine itself being used up. Over the polar regions, where atomic oxygen is scarce, two ClO molecules instead combine to form the dimer dichlorine peroxide (Cl2O2, often written ClOOCl); its photolysis in spring sunlight releases Cl atoms and drives the rapid ozone loss seen in the Antarctic ozone hole. Because it carries one unpaired electron, ClO is paramagnetic and short-lived, existing only transiently in the atmosphere.
Key facts
| Formula | ClO |
|---|---|
| Molar Mass | ≈ 51.45 g/mol |
| Field | Inorganic Chemistry |
| Nature | Paramagnetic free radical (odd-electron species) |
Satellite instruments measuring high ClO concentrations coincident with plunging ozone levels over Antarctica each September provided direct evidence linking chlorofluorocarbon-derived chlorine to the ozone hole.
Frequently asked questions
Why is ClO important for the ozone layer?
ClO is the central reactive intermediate in catalytic cycles, including the ClO-dimer cycle, that break down stratospheric ozone faster than it can be replenished, most dramatically in the Antarctic ozone hole.
Is chlorine monoxide the same as chlorine dioxide?
No. Chlorine monoxide (ClO) is a transient atmospheric radical with one oxygen atom, while chlorine dioxide (ClO2) is a stable, isolable compound used as a water disinfectant and bleaching agent.