Environmental Chemical Compound Writing Assignment - Research Paper Example

Dichlorodifluoromethane a) Introduction Dichlorodifluoromethane is a chemical belonging to a family of chemicals called chlorofluorocarbons. These were first developed in the 1930s. Dichlorodifluoromethane has the chemical formula CCl2F2. It is known by various names including: Algofrene type 2, carbon dichloride difluoride, dichloro-difluoromethane , chladone 12, dichlorodifluormethane, dichlor(difluor)methan, dichloro(difluoro)methane, Frigen R12 , khladon 12, Chlorofluorocarbon 12, Arcton 12, arcton 6, Fluorocarbon-12, electro-cf 12, Forane 12, eskimon 12, Fluorocarbon 12, Freon 12, Isceon 122, Frigen 12, Genetron 12, Halocarbon 12, Propellant 12 and Refrigerant R121 Its chemical structure is:b) Properties It is a non-corrosive, colourless gas2.

At low concentrations it is odourless, but at very high concentrations it has an odour similar to that of ether3. It has a melting point of -157.7⁰C and a boiling point of -29.8⁰C4. It is soluble in water and many other organic solvents such as benzene and cyclohenxanone5. It has a molecular weight of 120.913 and does not burn in air6. It is normally compressed and stored as liquefied gas7. It has a vapour pressure of 4850 mmHg8. c) Preparation Dichlorodifluoromethane is prepared by reacting carbon tetrachloride and hydrogen fluoride, using antimony pentachloride as a catalyst:d) Uses Because of the non-corrosive nature and very low boiling point of dichlorodifluoromethane, it was mainly used as a refrigerant in numerous home and industrial settings; it could not damage the mechanical components of the refrigerators.

It was also used as an aerosol propellant in many pharmaceutical products such as Salbutamol and cosmetic sprays. Another use was in fire extinguishing systems, where it was used as a foaming agent. The chemical was also as an intermediate chemical in the production of other chemicals such as fluoropolymers9.e) Impact on environment Dichlorodifluoromethane was released into the environment during its production, transportation, storage and eventual use. Because of its high vapour pressure, any dichlorodifluoromethane that was released onto the ground quickly found its way into the atmosphere through volatilisation.

Once in the atmosphere, the chemical accumulated in the troposphere. In this part of the atmosphere, the chemical was found to be very stable because it did not photodissociate at the wavelengths of light higher than 200 nm found in the troposphere. It accumulated in the troposphere and then spread around the world, and then diffused into the stratosphere after around thirty years. Once in the stratosphere, the chemical underwent photodissociation, influenced by the strong, short wavelength UV light10: The chlorine radicals produced then catalytically reacted with the ozone as follows: These reactions contributed to the ozone destructions.

The fact that a chlorine atom gets regenerated in each catalytic cycle made even the smallest amounts of dichlorodifluoromethane extremely lethal to the ozone. Destruction of the ozone leads to increased amounts of UV rays reaching the ground. These UV rays increase the occurrence of cancers such as melanoma and carcinomas.f) Fate of the chemical The danger posed by dichlorodifluoromethane and other CFCs to the ozone led to the formation of the Montreal Protocol in 1987. The adoption of this treaty by countries the world over led to the reduction and eventual ceasing of production and use of CFCs11.

Based on the treaty, the ozone layer will be fully restored by 2050. Dichlorodifluoromethane, along with other CFCs is being used to trace the movement and mixing of ocean masses. Chlorofluorocarbons dissolve in ocean water and get carried to the ocean’s core. Because of the inert nature of CFCs, they are unaffected by natural chemical reactions in the ocean water. This makes it possible to plot their progress through the atmosphere to the ocean and the eventual mixing of waters.References: