Hydrochlorofluorocarbon HCFC

The 1990 Clean Air Act regulates the production and use of CFCs, hydrochlorocarbons, hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbon (HFC) substitutes. CFC and halon (Class I substances) usage is to be phased out in steps until total phaseout occurs on January 1,... 

In this sequence the Cl also acts as a catalyst and two molecules are destroyed. It is estimated that before the Cl is finally removed from the atmosphere in 1—2 yr by precipitation, each Cl atom will have destroyed approximately 100,000 molecules (60). The estimated O -depletion potential of some common CFCs, hydrofluorocarbons, HFCs, and hydrochlorofluorocarbons, HCFCs, are presented in Table 10. The O -depletion potential is defined as the ratio of the emission rate of a compound required to produce a steady-state depletion of 1% to the amount of CFC-11 required to produce the 1% depletion. The halons, bromochlorofluorocarbons or bromofluorocarbons that are widely used in fire extinguishers, are also ozone-depleting compounds. Although halon emissions, and thus the atmospheric concentrations, are much lower than the most common CFCs, halons are of concern because they are from three to ten times more destmctive to O, than the CFCs. 

Table 4. Physical Properties of Aliphatic Hydrochlorofluorocarbons (HCFCs) ...

CFC-113, CF2CICFCI2, or the hydrochlorofluorocarbons (HCFCs) such as HCFC-123, CF2CHCI2, HCFC-141b, or CH2CFCI2, are miscible in all proportions with the perfluoro compounds at 25°C. Typical solubiHty data are shown in Table 2. 

As you know, most countries are phasing out certain refrigerants to lessen damage to the ozone layer. The chemicals being phased out are chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Replacements are hydrofluorocarbons (HFCs) and certain blends. The DuPont web site (www.dupont.com) gives the handy Table I of recommended replacement refrigerants for various applications. 

Several of the commercially available 16,000 chlorinated and brominated compounds have already been regulated or harmed, CFCs, DDT and chlorinated biphenyls are typical examples. Many others are being phased out according to the Montreal Protocol on Substances that Deplete the Ozone Layer. This includes chlorinated solvents, methyl bromide and halons (e.g. CF3Br). The milder ozone destroyers, hydrochlorofluorocarbons (HCFCs) will also, eventually, be phased out. 

Acronyms for chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (MFCs)... 

Hydrochlorofluorocarbons (HCFCs) HCFC-225ca, 73 725 HCFC-225cb, 73 725 HCFC blowing agents, 25 469 HCG P-HCG (beta subunit human chorionic gonadotropin), 9 64 H-Coal process, 6 766, 838-841 HCV. See Hepatitis C virus (HBV)... 

Brock, W.J., Shin-Ya, S., Rusch, G.M., Hardy, C.J.. and Trochimowicz. H.J. Inhalation toxicity and genotoxicity of hydrochlorofluorocarbon HCFC-225ca and HCFC-225cb. J. Appl. Toxicol, 19(2) 101-112.1999. 

Substitutes for the CFCs that cause depletion of stratospheric ozone are being developed. Those which will be used in the near future (hydrochlorofluorocarbons, HCFCs) are of concern because a decomposition product, trifluoroacetic acid, might be very persistent and, under extreme conditions, have the potential to cause an undesirable environmental impact. 

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