Chlorofluorocarbons and ozone layer

https://www.youtube.com/watch?v=GhH77DcEv9M

What is ozone layer

Found in stratosphere around 20-40 km above earth’s surface

Contains a relatively high concentration of chemical ozone (O3)

The ozone later absorbs a great deal of the UV radiation from the sun

So protects living organisms from excessive UV exposure.

How does ozone layer protect us from UV radiation

In stratosphere, the UV radiation causes double bond in oxygen molecules to break like this, 2 oxygen radicals are formed (radical is species with an unpaired electron)

The oxygen radical then reacts with an oxygen molecule to form a molecule of ozone.

What are chlorofluorocarbons (CFCS)

They are haloalkanes

Ozone constantly breaks down and forms theoretically, but CFCS are molecule in the air that also cause the breakdown of ozone

CFCS are stable molecules, due to high bond enthalpy of carbon to halogen bonds, also non toxic

What happens when CFCS are in stratosphere

The uv radiation causes a carbon chlorine bond to break, this is called photodissociation, this is homolytic fission and produces a chlorine radical, highly reactive.

What happens in propagation step 1 and 2

A chlorine radical reacts with molecule of ozone, produces oxygen molecule plus a highly reactive chlorine monoxide radical

In step 2 , the chlorine monoxide radical reacts with oxygen radical

Now chlorine radical from step 2 can go back and trigger step 1 again

How is ozone destroyed by nitrogen oxide radicals

The nitrogen monoxide radical reacts with ozone to produce the nitrogen dioxide radical plus an oxygen molecule

The nitrogen dioxide radical then reacts with oxygen radical , forms another nitrogen monoxide radical plus an oxygen molecule

This takes place in a cycle.