HSC CHEMISTRY 2015​.

Origins of CFC's                 

 

Haloalkane: compounds in which one or more of the Hydrogen (H) atoms of an alkane has been replaced by a halogen atom.

 

Halon: Haloalkane in which all the hydrogen atoms have been replaced by bromine, chlorine and/or fluorine atoms.

 

Chlorofluorocarbon (CFC): Haloalkanes in which all the hydrogen atoms have been replaced by chlorine or fluorine atoms

Eg) 1,2,2-trichloro-1,1,2-triflourethane (CFC 113)

which is used for cleaning electronic circuit boards.  

 

 

Uses: Chlorofluorocarbons were developed in the 1930’s to replace ammonia

used as a refrigerant in refrigerators and air conditioners due to them being

non-toxic, unreactive and easily liquefied on compression. They were also used

as solvents in dry cleaning, propellants in spray-cans and as blowing agents to

expand plastics such as polystyrene foam by the 1980’s

 

Halons were used as fire extinguishing agents especially for large computer systems and on airplanes.

 

Problems: Many uses of CFC’s, such as aerosol cans, air-conditioners and circuit board cleaners, released CFC’s into the atmosphere. At the time this was not considered an issue due to their inertness and non-toxicity. However due to this inertness and their insolubility in water they are not removed from the atmosphere in rain or destroyed by sunlight or Oxygen, as most organic compounds are, and they dispersed evenly around the globe. As their concentrations in the troposphere increased they began to diffuse into the stratosphere where they began to cause issues.