CFCs and HCFCs are usually produced by halogen exchange starting from chlorinated methanes and ethanes.
Illustrative is the synthesis of chlorodifluoromethane from chloroform: The brominated derivatives are generated by free-radical reactions of the chlorofluorocarbons, replacing C-H bonds with C-Br bonds.
Because of their polarity, the CFCs are useful solvents, and their boiling points make them suitable as refrigerants.
The CFCs are far less flammable than methane, in part because they contain fewer C-H bonds and in part because, in the case of the chlorides and bromides, the released halides quench the free radicals that sustain flames.
Because the fluorine and chlorine atoms differ greatly in size and effective charge from hydrogen and from each other, the methane-derived CFCs deviate from perfect tetrahedral symmetry.
The physical properties of CFCs and HCFCs are tunable by changes in the number and identity of the halogen atoms.
In general they are volatile, but less so than their parent alkanes.
Fluoride is helpful in preventing tooth decay and is used in tap water and toothpaste.
It is pale greenish-yellow in color with a pungent odor. Many of the reactions with fluorine are sudden and explosive.
Fluorine will burn all sorts of compounds and elements including water, copper, gold, and steel. Because it is so reactive, fluorine does not occur as a free element in nature.
Bromine atoms are even more efficient catalysts; hence brominated CFCs are also regulated.
CFCs and HCFCs are used in a variety of applications because of their low toxicity, reactivity and flammability.
They are also commonly known by the Du Pont brand name Freon.