Atmospheric Chemistry and the Ozone Layer

Ozone (O3) is constantly produced and destroyed in the stratosphere, and its presence plays a vital role in shielding us from harmful UV radiation emitted by the sun. It is believed that life could not have flourished on land without this protective ozone layer, and instead, life would have been restricted to the depths of the ocean. The ability of ozone to protect us from harmful radiation is believed to result from the following mechanism  

An illustration of the ability of stratospheric ozone to convert light into heat. 

An iiiustration of the hoie in the ozone iayer over Antarctica. 

The second propagation step regenerates a chlorine radical, which continues the chain reaction. In this way, each CFC molecule can destroy thousands of ozone molecules. Awareness of the effect of CFCs led to a ban on their production in most countries as of January 1, 1996, as part of a global treaty called the Montreal Protocol on Substances that Deplete the Ozone Layer. As a result, much research has been directed toward flnding suitable substitutes, such as the following two categories of compounds. 

Hydrochlorofluorocarbons (HCFCs) are compounds that possess at least one C—H bond. Below are a few examples  

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Cicerone, R. J., Fires, Atmospheric Chemistry, and the Ozone Layer, Science, 263, 1243-1244 (1994). 

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