What are the reactions involved in ozone layer depletion in the stratosphere?
UV reactions on oxygen causes the formation of ozone in the stratosphere.
1. 
2. 
CFC molecules are made up of chlorine, fluorine and carbon atoms and are extremely stable. This extreme stability allows CFC's to slowly make their way into the stratosphere. This prolonged life in the atmosphere allows them to reach great altitudes where photons are more energetic. When the CFC's come into contact with these high energy photons, their individual components are freed from the whole.
Cl+O3 → ClO+O2 (step 1)
ClO+O.→Cl+O2 (step 2)
O3 + O.→2O2 (Overall reaction)
Chlorine is able to destroy so much of the ozone because it acts as a catalyst. Chlorine initiates the breakdown of ozone and combines with a freed oxygen to create two oxygen molecules. After each reaction, chlorine begins the destructive cycle again with another ozone molecule.