Chlorofluorocarbons CFCs are organic compounds containing carbon, chlorine, and fluorine atoms. They were widely used as refrigerants, propellants, and solvents until it was discovered that they contribute to the depletion of the ozone layer in the Earth's stratosphere. The breakdown of ozone molecules by CFCs occurs through a series of chemical reactions known as the ozone depletion cycle.The mechanism of this process involves the following steps:1. Photodissociation of CFCs: When CFCs are released into the atmosphere, they eventually rise into the stratosphere, where they are exposed to ultraviolet UV radiation from the sun. The UV radiation causes the CFC molecules to break apart, or photodissociate, releasing chlorine atoms. For example, when CFC-12 CCl2F2 is exposed to UV radiation, it breaks down into a chlorine atom and a carbon-chlorine-fluorine radical:CCl2F2 + UV Cl + CClF22. Reaction of chlorine atoms with ozone: The chlorine atoms released in the first step can then react with ozone O3 molecules, breaking them down into oxygen molecules O2 and chlorine monoxide ClO :Cl + O3 ClO + O23. Reaction of chlorine monoxide with oxygen atoms: The chlorine monoxide ClO formed in the previous step can react with oxygen atoms O produced by the photodissociation of ozone molecules. This reaction regenerates the original chlorine atom and forms an oxygen molecule:ClO + O Cl + O24. Catalytic cycle: The chlorine atom produced in the third step can then react with another ozone molecule, repeating steps 2 and 3. This creates a catalytic cycle in which a single chlorine atom can break down thousands of ozone molecules before it is eventually removed from the stratosphere through other chemical reactions.The overall reaction for the ozone depletion cycle can be represented as:O3 + O 2 O2This process reduces the concentration of ozone in the stratosphere, leading to the formation of the ozone hole and allowing more harmful UV radiation to reach the Earth's surface. In response to this issue, the production and use of CFCs have been significantly reduced under the Montreal Protocol, an international agreement aimed at protecting the ozone layer.