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Environmental effects of haloalkanes You will:know the usage of some important haloalkanesbe able to identify the environmental problems associated with the influence of halogenoalkanes; How do Chlorofluorocarbons affect the environment?  Usage and environmental effects of haloalkanes We have already seen that haloalkanes are important intermediates in the synthesis of a wide variety of substances. Some uses of haloalkanes are given below.Freons are the technical name of polyhaloalkanes, which are used as refrigerants. Most often used in air conditioners and refrigerators. They use the process of evaporation of a liquid. Fluid freons, which evaporate very readily and are liquefied, are passed through sealed tubes located in a cooled space, where freons evaporate, causing cooling. Then the gaseous freon enters the compressor, where it is liquefied and can be reused in the evaporator. Removing gases from the freon tubes  520396174It is assumed that freons contribute to the destruction of the protective ozone layer in the upper atmosphere. This ozone layer protects the Earth’s atmosphere from the dangerous effects of ultraviolet radiation from the sun, the destruction of the ozone layer can cause serious damage to all living organisms. Freons are used not only in refrigeration machines, where they can accidentally get into the atmosphere but also in aerosol cans, although such use is now being condemned. Ozon layer  7766241971,2-Dibromoethane (ethylene dibromide) has long been used as a fumigant, until in 1984 its carcinogenic effect was found. Now its use in some countries is prohibited.1,2-Dichloroethane (ethylene dichloride) is used as a solvent to remove stains from clothing and fabrics.Carbon tetrachloride (carbon tetrachloride) and chloroform (trichloromethane) are used in the laboratory as solvents. At the same time, certain precautions must be observed, since these substances are hazardous to health. Carbon tetrachloride used to be used for dry cleaning clothes sometimes used to extinguish fires. But, since the ingress of carbon tetrachloride into the flame produces poisonous substances, its use is limited. Chloroform is used as an anesthetic. Molecular model of liquid CCl4  120492922 Dichlorodiphenyltrichloroethane (DDT) and analogues The cultivation of some crops on large areas is impossible today without the use of insecticides. But there are still people who collected the Colorado beetle in bottles of kerosene, and the leaders of collective farms with children were calculated for the number of beetles collected per day. Increased locust invasions, leaving the naked land, other pests that in a few days destroyed the crop of crops, set the scientists the task – in the shortest possible time to find a way to destroy pests. Of the proposed measures, the most effective was the use of powder DDT.Chemically pure DDT is a crystalline powder, odorless. Rapidly soluble in organic solvents. In water, only forms an emulsion. According to the results of numerous studies, chemists came to the conclusion that a chemically pure drug DDT is toxic for fish, insects, cold-blooded and small warm-blooded representatives of the animal world. The drug is toxic to large warm-blooded and human, but without fatal outcome.Developed chemically pure insecticide DDT was highly effective in combating the carriers of epidemic diseases (mosquitoes, fleas, mosquitoes, …), pests of crops, including locusts, doomed people and animals to starvation. Its high toxicity is confirmed by the following example: for the death of the larva of the housefly, it is sufficient to contact one-millionth milligram of powder. The drug was economically advantageous: once treated surface remains deadly for insects for a long time and does not require re-treatment. Fogging DDT spray to kill mosquito for control Malaria 420197731 DDT molecule 172673789Danger of exposure to DDT on human healthWhen insecticides are used to kill insects, it enters the food chain, which closes the person or large warm-blooded representatives of the fauna. By results of researches concentration of DDT in each link of a food chain increases in 10 times. After falling into the soil after washing with rain, DDT is included in the food chain soil-silt-algae-small aquatic organisms-predator fish and other animals. DDT practically does not work on soilworms. If you take the content of DDT in bottom silt for 1 ?g, then in fish its amount increases to 3-6 mg / kg of mass or on average 10,000 times. In the body of seagulls, consuming such fish, the concentration increases to 200 mg / kg of mass. Repeated use of contaminated fish in human food, no doubt, contributes to the accumulation of DDT in the body.Residual quantities of an unrelated human body substance accumulate over time, although extremely slowly, but constantly. From the human body, DDT is excreted only in the mother’s milk and passed on to the newborn. Therefore, it is found in the second and subsequent generations, whose ancestors have received certain amounts of DDT with food or other means. When you consume large amounts of food containing high amounts of DDT the negative health effects are felt by illness and discomfort, but do not cause immediate death. Attributed to DDT and the impact on the development of cardiovascular diseases, atypical pneumonia, hepatitis and others. Its accumulation helps to reduce the reproductive function of birds and some mammals, including bats. It is highly toxic to cold-blooded invertebrates and fish. The high risk of DDT is that when it accumulates in the body, it migrates over long distances around the world. Bromochlorodifluoromethane and bromotrifluoromethane are used in fire extinguishers. 584227195

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