Community hub
Recent from talks
Knowledge base stats:
Talk channels stats:
Members stats:
Chlorofluorocarbon
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F). They are produced as volatile derivatives of methane, ethane, and propane.
The most common example of a CFC is dichlorodifluoromethane (R-12). R-12, also commonly called Freon, is used as a refrigerant. Many CFCs have been widely used as refrigerants, propellants (in aerosol applications), gaseous fire suppression systems, and solvents. As a result of CFCs contributing to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol, and they are being replaced with other products such as hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs) including R-410A, R-134a and R-1234yf.
As in simpler alkanes, carbons in CFCs bond with tetrahedral symmetry. Because the fluorine and chlorine atoms differ greatly in size and effective charge from hydrogen and from each other, methane-derived CFCs deviate from perfect tetrahedral symmetry.
The physical properties of CFCs and HCFCs can be affected by changes in the number and identity of the halogen atoms. They are generally volatile, but less so than their parent alkanes. The decreased volatility is attributed to the molecular polarity induced by the halides, which induces intermolecular interactions. Thus, methane boils at −161 °C whereas the fluoromethanes boil between −51.7 (CF2H2) and −128 °C (CF4). CFCs still have higher boiling points because the chloride is even more polarizable than fluoride. Because of their polarity, CFCs are useful solvents, and their boiling points make them suitable as refrigerants. 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.
The densities of CFCs are higher than their corresponding alkanes. In general, the density of these compounds correlates with the number of chlorides.
CFCs and HCFCs are usually produced by halogen exchange starting from chlorinated methanes and ethanes. Written below is the synthesis of chlorodifluoromethane from chloroform:
Brominated derivatives are generated by free-radical reactions of hydrochlorofluorocarbons, replacing C–H bonds with C–Br bonds. The production of the anesthetic 2-bromo-2-chloro-1,1,1-trifluoroethane ("halothane") is written out below:
CFCs and HCFCs are used in various applications because of their low toxicity, reactivity and flammability. Every permutation of fluorine, chlorine and hydrogen based on methane and ethane has been examined and most have been commercialized. Furthermore, many examples are known for higher numbers of carbon as well as related compounds containing bromine. Uses include refrigerants, blowing agents, aerosol propellants in medicinal applications, and degreasing solvents.
Hub AI
Chlorofluorocarbon AI simulator
(@Chlorofluorocarbon_simulator)
Chlorofluorocarbon
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F). They are produced as volatile derivatives of methane, ethane, and propane.
The most common example of a CFC is dichlorodifluoromethane (R-12). R-12, also commonly called Freon, is used as a refrigerant. Many CFCs have been widely used as refrigerants, propellants (in aerosol applications), gaseous fire suppression systems, and solvents. As a result of CFCs contributing to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol, and they are being replaced with other products such as hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs) including R-410A, R-134a and R-1234yf.
As in simpler alkanes, carbons in CFCs bond with tetrahedral symmetry. Because the fluorine and chlorine atoms differ greatly in size and effective charge from hydrogen and from each other, methane-derived CFCs deviate from perfect tetrahedral symmetry.
The physical properties of CFCs and HCFCs can be affected by changes in the number and identity of the halogen atoms. They are generally volatile, but less so than their parent alkanes. The decreased volatility is attributed to the molecular polarity induced by the halides, which induces intermolecular interactions. Thus, methane boils at −161 °C whereas the fluoromethanes boil between −51.7 (CF2H2) and −128 °C (CF4). CFCs still have higher boiling points because the chloride is even more polarizable than fluoride. Because of their polarity, CFCs are useful solvents, and their boiling points make them suitable as refrigerants. 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.
The densities of CFCs are higher than their corresponding alkanes. In general, the density of these compounds correlates with the number of chlorides.
CFCs and HCFCs are usually produced by halogen exchange starting from chlorinated methanes and ethanes. Written below is the synthesis of chlorodifluoromethane from chloroform:
Brominated derivatives are generated by free-radical reactions of hydrochlorofluorocarbons, replacing C–H bonds with C–Br bonds. The production of the anesthetic 2-bromo-2-chloro-1,1,1-trifluoroethane ("halothane") is written out below:
CFCs and HCFCs are used in various applications because of their low toxicity, reactivity and flammability. Every permutation of fluorine, chlorine and hydrogen based on methane and ethane has been examined and most have been commercialized. Furthermore, many examples are known for higher numbers of carbon as well as related compounds containing bromine. Uses include refrigerants, blowing agents, aerosol propellants in medicinal applications, and degreasing solvents.