Chlorofluorocarbons trichloromonofluoromethane

Dichlorodifluoromethane, dichlorotetrafluoroethane, and trichloromonofluoromethane are chlorofluorocarbon (CFC) aerosol propellants used in pharmaceutical formulations. 

Dichlorodifluoromethane is used as an aerosol propellant in metered-dose inhaler (MDI) formulations, either as the sole propellant or in combination with dichlorotetrafluoroethane, trichloromonofluoromethane, or mixtures of these chlorofluorocarbons. Dichlorodifluoromethane may also be used as a propellant in an aerosolized sterile talc used for intrapleural administration and is also used alone in some MDIs containing a steroid. 

Blends of trichloromonofluoromethane and dichlorodifluoromethane (propellant 11/12) or propellant 11/114/12 produce vapor pressures of 103 84 kPa (15-70 psig) at 21°C, which adequately cover the range of pressures required to produce the proper particle-size distribution for satisfactory aerosol products. Trichloromonofluoromethane is unique among the chlorofluorocarbon propellants in that it is a liquid at room temperature and atmospheric pressure and can be used to prepare a slurry with insoluble medicinal agents. 

Although nonflammable, when heated to decomposition chlorofluorocarbons emit toxic fumes containing phosgene and fluorides. Although not as volatile as dichlorodifluoroethane or dichlorotetrafluoroethane, trichloromonofluoromethane should be handled as indicated above. Since it is a liquid at room temperature, caution should be exercised in handling this material to prevent spillage onto the skin. It is an irritant to the eyes. 

Although the CFCs are not as stable as the fluorocarbons (FCs), they are unusually stable compounds. Dichlorodifluoromethane, CCI2F2 (CFC-12), is stable at 500°C in quartz. Trichloromonofluoromethane, CCI3F (CFC-11), begins to decompose at 450° C. The CFCs react with molten alkali metals and CCI2F2 reacts vigorously with molten aluminum, but with most metals they do not react below 200°C. An exception is the dechlorination of chlorofluorocarbons with two or more carbon atoms in the presence of Zn, Mg, or A1 in polar solvents. ... 

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