Fluorine compounds chlorofluorocarbons

Properties. The physical properties of aHphatic fluorine compounds containing chlorine are similar to those of the PECs or HECs (3,5). They usually have high densities and low boiling points, viscosities, and surface tensions. The irregularity in the boiling points of the fluorinated methanes, however, does not appear in the chlorofluorocarbons. Their boiling points consistently increase with the number of chlorines present. The properties of some CECs and HCECs are shown in Tables 3 and 4. 

CFG = chlorofluorocarbon HCFC = hydrochlorofluorocarbon see Fluorine compounds,organic-aliphatic. 

Fluorinated compounds are frequently referred lo by code, such as F-l 15. To translate this code into a molecular formula, add 90 to 115. The firsl digit of the sum is the number of carbons the second, the number of hydrogens the third, the number ol fluorines chlorines complete the valences (i.e., C2F5CI is F-l 15 = 90 + 115 = 205. or C H Fj). A four-digit number is used for unsaturated molecules. See Tables 14.1-14.3 for the numbering system for chlorofluorocarbons. 

Most other simple compounds whose history has been examined have been those of obvious industrial interest. Thus, fluorinated compounds have been discussed, especially the now controversial chlorofluorocarbons (CFCs).80 Another aliphatic chemical that has received exhaustive historical treatment, chiefly in the context of its industrial use, is lactic acid.81 The development of urea as a fertilizer has been studied,82 and a history provided of the synthesis of methanol.83... 

Loss rates of both CCI4 and Fll in anoxic waters are probably due to biological rather than chemical removal (Lee et al., 1999). It also seems likely that some of the chlorofluorocarbons are removed in fully oxygenated surface waters. Observations show that there is a deficit of CCI4 in the Antarctic surface and bottom waters (Meredith et al., 1996). Finally, fluorinated compounds such as CFC-113 are degraded in warm surface waters of the temperate North Atlantic, the tropical western Pacific, the Eastern Mediterranean, and even the Weddell Sea (Roether et al., 2001). CFC-113 depletions were —3% yr, with possibly accelerated rates in the mixed layer or near the surface. 

A carbon atom can be bonded to as many as four halogen atoms, so an enormous number of organic halides can exist. Completely fluorinated compounds are known as fluorocarbons or sometimes perfluorocarbons. The fluorocarbons are even less reactive than hydrocarbons. Saturated compounds in which all H atoms have been replaced by some combination of Cl and F atoms are called chlorofluorocarbons or sometimes freons. These compounds were widely used as refrigerants and as propellants in aerosol cans. However, the release of chlorofluorocarbons into the atmosphere has been shown to be quite damaging to the earth s ozone layer. Since January 1978, the use of chlorofluorocarbons in aerosol cans in the United States has been banned, and efforts to develop both controls for existing chlorofluorocarbons and suitable replacements continue. The production and sale of freons have been banned in many countries. 

Throughout this chapter, we ve learned quite a bit about the coimection between the properties of PTFE and the chemical bonds that hold the polymer together. Although the discovery of PTFE was accidental, it is widely recognized as an extremely useful and beneficial material. But another group of fluorine-containing compounds, chlorofluorocarbons (CFCs), has a much different history. We U close this chapter by looking at some of the uses and unintended consequences of CECs. 

Fluorine compounds have many uses. One of the most notable of these is the manufacture of chlorofluorocarbon compounds known by the trade name Freon. These are chemical combinations of chlorine, fluorine, and carbon, an sample of which is dichlorodifluoromethane, CI2CF2. These compounds used to be widely employed as refrigerant fluids and blowing agents to make foam plastics they were also once widely used as propellants in aerosol spray cans. Uses of chlorofluorocarbons have now been phased out because of their role in destroying stratospheric ozone (discussed with oxygen, above). 

The term fluorocarbons is defined here as carbon compounds containing fluorine. If they contain only fluorine, they are sometimes referred to as FCs. The compounds may also contain chlorine, bromine, or hydrogen. Other descriptive names include chlorofluorocarbons (CFCs), fluorinated compounds, and halogen-ated hydrocarbons. Hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (FIFOs) are compounds in this family that contains hydrogen. Unless otherwise specified, the term fluorocarbons in this monograph applies to FCs, CFCs, HCFCs, and HFCs. 

Chlorofluorocarbons (CFCs) Aliphatic carbon compounds containing both chlorine and fluorine atoms. 

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