During the ozone depletion process, what initiates the homolytic fission of the C-Cl bond in CFCs?

The homolytic fission of the C-Cl bond in chlorofluorocarbons (CFCs) is primarily initiated by UV radiation. When CFCs are exposed to ultraviolet light, high-energy photons are absorbed, leading to the breaking of chemical bonds within the molecule. This process generates chlorine radicals, which are highly reactive and contribute to the depletion of ozone in the stratosphere.

This initiation step is critical because the energy provided by UV radiation is sufficient to overcome the bond dissociation energy of the C-Cl bond. Once the bond is broken, the chlorine radical can further react with ozone (O3), leading to a chain reaction where ozone is broken down into oxygen molecules (O2). This highlights the role of UV radiation as a catalyst in ozone depletion, distinguishing it from other factors like temperature, pressure changes, or reactions with water, which do not directly cause the homolytic fission of CFCs.