Chlorofluorocarbons substitutes

Harris JW, Pohl LR, Martin JL, et al. Tissue acylation by the chlorofluorocarbon substitute 2,2-dichloro-l,l,l-trifluoroethane. Proc Natl Acad Sci USA 1991 88(4) 1407—1410. 

M. Yamabe, "HCEC-225s as CEC-113 Substitutes" in Symposium on Progress on the Depelopment and Use of Chlorofluorocarbon (CEC) Altematipes, 200th ACS national Meeting, Abstract No. 22, Washington, D.C., Aug. 28, 1990. 

Freons. types of chlorofluorocarbons, at one time were used extensively in spray cans and as coolants in refrigerators and air conditioners. Unfortunately, they contribute to global warming and attack the Earth s protective ozone layer. One of the most promising substitutes is C2H2F4, which is called HFC-134a in industry. The reaction... 

Fluorosilicones and Fluorocarbons. Early defoamers to remove gas from crude oil consisted of chlorofluorocarbons. The use of these compounds has essentially ceased. They were substituted gradually by pure fluorosilicones [302], A formulation that is free of chlorofluorocarbons was described in the early 1990s. 

The two SCFs most often studied—CO2 and water—are the two least expensive of all solvents. CO2 is nontoxic and nonflammable and has a near-ambient critical temperature of 31. UC. CO2 is an environmentally friendly substitute for organic solvents including chlorocarbons and chlorofluorocarbons. Supercritical water (Tc = 374°C) is of interest as a substitute for organic solvents to minimize waste in extraction and reaction processes. Additionally, it is used for hydrothermal oxidation of hazardous organic wastes (also called supercritical water oxidation) and hydrothermal synthesis. (See also Sec. 15 for additional discussion of supercritical fluid separation processes.)... 

For the next thirty years, Thomas Midgley was revered as a scientist who had made our lives healthier and happier. Only in the closing decades of the twentieth century could other scientists detect the far-reaching damage caused by our reliance on his leaded gasoline and chlorofluorocarbon refrigerants. Yet such was his creativity that many years ago he and his associates also invented some of today s substitutes for their destructive CFCs. 

Hoet, P. et al., Epidemic of liver disease caused by hydrochlorofluorocarbons used as ozone-sparing substitutes of chlorofluorocarbons, Lancet, 350, 556, 1997. 

PCB polychlorinated biphenyls, TBT tributyl tin, CFC chlorofluorocarbons Cf e.g. the substitution principle in the German Ordinance on Hazardous Substances ( 16 and 36). Please refer to Technical Rules for Hazardous Substances TRGS 440 for the recommended procedure of substitution. 

When some of the chlorines are replaced by hydrogens, CFCs become HCFCs, the now more common nomenclature for those chlorofluorocarbons containing hydrogen. The numbering is the same. When more than one isomer is possible, the most symmetrically substituted compound has only a number letters a and b are added to designate less symmetrical isomers. 

Chlorobenzene, homolysis of tert-butyl phenylperacetates, 900-2 Chlorofluorocarbons (CFCs) in atmosphere, 604 substitutes, 138... 

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). 

Methane is removed continually from the atmosphere by reaction with OH radicals (Section 8.3). In contrast, chlorofluorocarbons and related volatile compounds are inert under the conditions of the lower atmosphere (troposphere), so atmospheric concentrations of these refrigerants and solvents will tend to increase as long as releases continue. The chief concern over chlorofluorocarbons is that they are a major factor in destruction of the stratospheric ozone layer (Section 8.3). They have been banned under the Montreal Protocol of 1988, but it is important that whatever substitutes (inevitably greenhouse active) are introduced to replace them degrade relatively quickly in the troposphere to minimize any contribution they may be capable of making to greenhouse warming. 

Chlorine can be substituted by hydrogen fluoride and boron trifluoride to yield chlorofluorocarbon compounds. This process is applied for producing 1,1-dichloro-l-fluoroethane (14), which is considered as a replacement for trichlorofluoromethane as a blowing agent for plastic foam.18... 

To protect life from ultraviolet radiation, international treaties now ban or phase out chlorofluorocarbons, and there is an effort to find safe substitutes. 

For the halogens, perhaps the most pressing concern is how the substitution of hydrohalocarbons for the fully halogenated chlorofluorocarbons... 

With the great commercial interest in chlorofluorocarbons, the addition of HF to unsaturated organic chlorides, particularly vinylic chlorides has received considerable industrial attention.4 3 13-19 While these reactions are more difficult to effect than those of simple alkenes and increasing halogen substitution about the C—C double bond decreases the alkene reactivity, the reactions of simple monochloroalkenes proceed at temperatures from -23 to +120 C and can give good yields. Trichloroethylene or 1,1,2-tri-chloropropene, on the other hand, require temperatures in excess of 200 C, and tetrahaloethylenes fail to react in the absence of a catalyst.3 However, substitution of fluorine for chlorine tends to facilitate HF addition.3... 

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