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Hydrochlorofluorocarbons (HCFCs) and chlorofluorocarbons (CFCs) are fully or partially halogenated hydrocarbons that are produced as volatile derivatives of propane, ethane, and methane. They contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F). Additionally, the DuPont brand name Freon is a common name for them. Dichlorodifluoromethane, also known as R-12 or Freon-12, is the most typical example. Numerous CFCs have been utilized extensively as solvents, propellants (for aerosol applications), and refrigerants. Under the Montreal Protocol, the production of CFCs has been phased out and is being replaced by other products like hydrofluorocarbons because they contribute to ozone depletion in the upper atmosphere. The tetrahedral symmetry of the carbon bonds in CFCs is similar to that of simpler alkanes.