Question

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.

Answer 1

Uses of halogen-containing compounds:

Dichloromethane is used as a solvent, paint remover, propellant in aerosols, process solvent in the manufacture of drugs, metal cleaning and finishing solvent.

Trichloromethane is used as a solvent for fats, alkaloids, iodine and other substances.

Triiodomethane is used as an antiseptic But some compounds of this class are responding to exposure of flora and fauna to more and more UV light which causes destruction to great extent.

These are as follows:

(i) Tetrachloromethane: When carbon tetrachloride is released into the air, it rises to the atmosphere and depletes the ozone layer. Depletion of the ozone layer is believed to increase human exposure to UV rays leading to increased skin cancer, eye diseases and disorders, and possible disruption of the immune system. These UV rays cause damage to plants and a reduction of plankton populations in the ocean’s photic zone.

(ii) Freons: The chlorofluorocarbon compounds of methane and ethane are collectively known as freons. Here, it provides chlorine atoms which damage the ozone layer. Because of this depletion UV rays enters our atmosphere and become responsible for damage to a great extent.

(iii) p,p’-Dichlorodiphenyltrichloroethane(DDT): DDT is not completely biodegradable. Instead, it gets deposited in fatty tissues. If ingestion continues for a long time, DDT builds up within the animal and affects the reproductive system.

To minimise the harmful impacts of these compounds i.e., freons, hydrofluorocarbons, and fluorocarbons which are stable in the stratosphere should be used in aerosol propellants and air conditioning equipment. The use of DDT was banned in the United States, although it is still in use in some other parts of the world.