Breakdown in the Atmosphere

The concern over the effects of chlorofluoro-carbons on the ozone layer has led to a rapid increase in understanding of atmospheric breakdown-mechanisms, particularly those involving chlorine atoms. Although UV light plays a crucial part in the balance of the ozone layer, direct photodegradation is not an important mechanism in the disappearance of chlorocarbons in the atmosphere [39, 40]. 

Much more significant is reaction with hydroxyl radicals, which are themselves formed photolytically, but many other molecules, and free radicals are involved. The decomposition of Carbon Tetrachloride (and F 11 and F 12), which are the only halogenated compounds which reach the stratosphere in any quantity, is initiated there by direct photolytic production of a chlorine atom some of the other 

Methyl chloride 0.14 12 230 200 Phosgene, chlorine, formyl chloride 

T richloroethylene 2.2 1 Phosgene, formyl chloride dichloro-acetic acid 

Perchloroethylene 0.17 10 Phosgene, Cl2C(OH)COCl, chlorine, trichloroacetic acid 

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