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Question

Chemistry Question on Haloalkanes and Haloarenes

Which of the following is responsible for depletion of the ozone layer in the upper strata of the atmosphere?

A

Polyhalogens

B

Ferrocenes

C

Fullerenes

D

Freons

Answer

Freons

Explanation

Solution

Freons or chlorofluoro carbons are responsible for depletion of the ozone layer in the upper strata of the. atmosphere. They are used as propellants, aerosol spray caps, refrigerents, fire fighting reagents etc. They are stable and chemically inert compounds. They absorb UV-radiation and break down liberating free atomic chlorine which causes decomposition of ozone through free radical reaction. This results in the depletion of the ozone layer. Freons are mainly Freon-1 (CFCl3)\left( CFCl _{3}\right) and Freon-12 (CF2Cl2)\left( CF _{2} Cl _{2}\right). They form free radical of chlorine in presence of UV-radiation. Such free radical decomposes O3O _{3} as follows Cl+O3ClO+O2Cl^{\bullet} + O_3 \to ClO^{\bullet} + O_2 ClO+O3ClChlorine free radical+2O2ClO^{\bullet} + O_3 \to \underset{\text{Chlorine free radical}}{Cl^{\bullet}} + 2O_2