Chlorofluorocarbons dichlorodifluoromethane

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. 

It is the use of LIDAR devices as tools for spectroscopic measurements on the various gases present in the atmosphere which concerns us here. These include ozone, carbon dioxide, the CFCs (chlorofluorocarbons, such as CFC-11, trichlorofluoromethane, and CFC-12, dichlorodifluoromethane, used as refrigerants) and all those molecules regarded as atmospheric pollutants. 

Unfortunately, the thermodynamically favored reactions of trichlo-rolluoromethane (CFC-11) and dichlorodifluoromethane (CFC-12) with water do not proceed to a significant degree below 300 C and at least 200 atm (1 atm = 101.325 kPa) or greater [42] (equation 44) Even at 4000 atm randoimzation rather than complete hydrolysis occurs, leaving another chlorofluorocarbon, chlorotri-fluoromethane (CFC-13), which is also potentially harmful to the earth s ozone layer... 

An efficient catalyst for thermal isomenzations of halofluorocarbons [6, 7, 8, 9] IS prepared by treatment of alumina with dichlorodifluoromethane at 200-300 °C [9] or aluminum chloride with chlorofluorocarbons in the presence of metals [W] or palladium on alumina [II These catalysts are far more efficient than aluminum halides themselves (equations 1 and 2)... 

Chlorofluorocarbon-blown foam blocks are used to insulate the walls and roofs of some buildings, thus reducing heat losses and helping to conserve fossil fuels. In this area, polyurethane foam competes with polystyrene foam, which until recently was blown with dichlorodifluoromethane (CFC 12) but is now blown with a mixture of chlorodifluoromethane (HCFC 22) and 1 -chloro-l,l-difluoroethane (HCFC 142b). 

The formed mixture is composed of trichlorofluoromethane (Freon-11) and dichlorodifluoromethane (Freon-12). These compounds are used as aerosols and as refrigerants. Due to the depleting effect of chlorofluorocarbons (CFCs) on the ozone layer, the production of these compounds may be reduced appreciably. 

Chlorination of methane, in which chlorine is substituted for one to all four of the hydrogens in methane, produces methyl chloride (CH3C1), methylene chloride (CH2C12), chloroform (CHC13), and carbon tetrachloride (CCf). The substitution of chlorines and fluorines in methane results in chlorofluorocarbons (see Dichlorodifluoromethane). 

Salmeterol xinafoate inhalation aerosol contains salmeterol xinafoate as the racemic form of the 1-hydroxyl-naphthoic acid salt of salmeterol. It is a pressurized, metered-dose aerosol unit for oral inhalation. It contains a microcrystalline suspension of salmeterol xinafoate in a mixture of two chlorofluorocarbon propellants (trichlorofluoromethane and dichlorodifluoromethane)... 

Maltoni, C., Lefemine, G, Tovoli, D. Perino, G. (1988) Long-term carcinogenicity bioassays on three chlorofluorocarbons (trichlorofluoromethane, dichlorodifluoromethane. chlorodi-fluoromethane) administered by inhalation to Sprague-Dawley rats and Swiss mice. Ann. N.Y. Acad. Sci., 534, 261-283... 

A group of compounds were discovered in the 1930s and were called the chlorofluorocarbons (CFCs). Because of their inertness they found many uses, especially as a propellant in aerosol cans. CFC-12 or dichlorodifluoromethane, CF2C12, was one of the most popular CFCs in use in aerosols. Scientists believe that CFCs released from aerosols are destroying the ozone layer and steps are being taken to reduce this threat. 

Chlorofluorocarbons. 1,1,1 -trichloro-2,2,2-trifluoroethane trichlorofluoromethane, dichlorodifluoromethane chlorodifluoro-methane l,2-dichloro-l,l,2,2-tetrafluoroethane chloropentafluo-roethane... 

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

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. 

Dichlorodifluoromethane and dichlorotetrafluoroethane are usually encountered as a liquefied gas and appropriate precautions for handling such materials should be taken. Eye protection, gloves, and protective clothing are recommended. These propellants should be handled in a well-ventilated environment. Chlorofluorocarbon vapors are heavier than air and do not support life therefore, when cleaning large tanks that have contained chlorofluorocarbons, adequate provisions for supply of oxygen in the tanks must be made in order to protect workers cleaning the tanks. 

The production of chlorofluorocarbons, or CFCs, has been banned by international treaty because of their deleterious effect on the ozone layer. The ozone layer absorbs much of the Sun s dangerous UV radiation before it reaches the Earth s surface. CFCs are extremely stable in the lower atmosphere (one reason why they are so useful), but when they reach the stratosphere they decompose, producing potent catalysts of ozone destruction. Ozone destruction is most evident above Antarctica during the spring, when this region is exposed to the Sun for the first time in months. Dichlorodifluoromethane (CF2CI2) is a typical CFC. 

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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