Some halogen containing compounds are useful in daily life. Some compounds of this class are responsible for exposure of flora and fauna to more and more of UV light which causes destruction to a great extent. Name the class of these halocompounds. In your opinion, what should be done to minimise harmful effects of these compounds ?

Explanation

A number of polyhalogen compounds, such as dichloromethane `(CH_2Cl_(2))`, chloroform `(CHCl_3)`, iodoform `(Chl_(3))`, carbon tetrachloride `(C Cl_(4))`, freons and DDt have a variety of application in our daily life. Freons are mostly used for aerosol propellants, refregeration and air conditioning purpose. Since freons (chlorogluoro compounds, they eventually go to the atmosphere from where they diffuse unchanged into the stratosphere. In stratosphere, freons are able to initiate radical chain reactions that can upset the natural ozone balance causing depletion of ozone layer. Thus more UV rays reach the earth which, in turn, damage of flora and fauna. To minimise the harmful effects of freons, hydrochlorofluorocarbons (HCFCs), such as `CHCiF_(2)` (called freon-22), `CHCl_(2)F` and hydrofluorocarbons (HFCs), such as `FCH_(2)CH_(2)F(HFC-152)` may be used as substitutes for chloroflurocarbons. Due to the presence of C-H bonds, such compounds are generally destroyed at lower altitudes before they reach the stratosphere.