Organic Chlorofluoro Hydrocarbons

摘要: The chlorofluorocarbons (CFCs) were introduced in the 1930s as “safe” replacements for refrigerants such sulfur dioxide, ammonia, carbon tetrachloride, and chloroform. In World War II, they used to produce insecticide aerosols protect troops tropical areas against malaria other insectborne diseases. During next 40–50 years, number type of applications expanded include foam blowing, precision cleaning, propellants medicinal, cosmetic, general-purpose aerosols, air conditioning, refrigeration. These uses eventually resulted emission CFCs into atmosphere. Because their low chemical reactivity, typically have long atmospheric residence times, a consequence, are distributed globally. In 1974 Molina Rowland hypothesized that, once reach stratosphere, will undergo breakdown release chlorine atoms. atoms could then react with stratospheric ozone breaking it down oxygen. Since absorbed much sun's ultraviolet β radiation (UVB), decreased levels would lead increases ground-level UVB. This affect crop growth cataracts nonmelanoma skin cancers. Following reports marked drop column over Antarctica (the “ozone hole”) during Antarctic winter, 1987 most nations world drafted signed an agreement calling phaseout CFCs. is known Montreal Protocol. Development was initiated on two types “in-kind” replacements. first hydrochlorofluorocarbons (HCFCs) second hydrofluorocarbons (HFCs). Both contain hydrogen susceptible attack by hydroxyl radicals present Therefore, shorter lifetime either not transported stratosphere or there only small amounts. HCFCs still capable causing depletion, although, since lifetimes short, ozone-depleting potential (ODP) lower than those associated HFCs do (or bromine, also depletion). They, therefore, cause depletion. A ranking scale has been developed using CFC11 reference compound, assigned value 1. values presented. A concern, regarding both replacements, that greenhouse warming gases. along substances trap infrared convert heat. However, good insulating materials, frequently use blowing agents refrigeration equipment can considerable energy savings, reducing dioxide emissions. potentials (GWPs) many CFCs, HCFCs, given. Many methods monitoring these substances. widespread concerns about environmental effects health effects, several reviews written materials. From well data presented later this chapter, be seen chemicals highly toxic. Some, fact, show significant signs toxicity at exposure up few percent even 5 10%. typical response following overexposure CNS depression related anesthetic properties chemicals. Also, some caused hepatotoxicity occasionally reproductive effects. Each compound discussed individually. They divided three general areas: chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons. Keywords: CFC 11-13; CFC 112-115; HCFC 21, 22, 123, 124, 132, 133a, 141b, 142b, HFC 32, 125, 1344a, 152a, 245fa; Ozone depletion potential; Chlorofluorcarbons; Greenhouse effect; Global warming; Atmospheric