Q.What are the reactions involved for ozone layer depletion in the stratosphere?

Ozone depletion in the stratosphere is caused mainly by chlorofluorocarbons (CFCs, e.g. Freons like CF2Cl2), which are chemically very stable in the lower atmosphere but slowly diffuse up into the stratosphere.

Step 1 — Photodissociation of CFCs:

In the stratosphere, CFC molecules absorb high-energy UV radiation, which breaks a C–Cl bond and releases a highly reactive chlorine free radical:

Step 2 — Chlorine radical attacks ozone:

This converts ozone to ordinary oxygen and produces chlorine monoxide radical.

Step 3 — Regeneration of the chlorine radical:

Here the ClO radical reacts with free oxygen atoms (present in the stratosphere from the natural O2/O3 equilibrium) to regenerate the chlorine radical.

Net reaction:

$\text{O}_3 + \text{O} \rightarrow 2\text{O}_2$ …

Present the three-step catalytic cycle: UV-driven release of Cl radical from a CFC, Cl radical reacting with O3, and ClO reacting with O to regenerate Cl — then sta …

• Forgetting that the chlorine radical is regenerated, which is exactly why it is so destructive (a catalyst, not consumed). …