Dichlorodifluoromethane
Structural formula | |||||||||||||||||||
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Wedge line formula to clarify the geometry | |||||||||||||||||||
General | |||||||||||||||||||
Surname | Dichlorodifluoromethane | ||||||||||||||||||
other names |
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Molecular formula | CCl 2 F 2 | ||||||||||||||||||
Brief description |
colorless, non-flammable gas with an ethereal odor |
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External identifiers / databases | |||||||||||||||||||
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properties | |||||||||||||||||||
Molar mass | 120.91 g mol −1 | ||||||||||||||||||
Physical state |
gaseous |
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density |
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Melting point |
−157.78 ° C |
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boiling point |
−29.8 ° C |
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Vapor pressure |
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solubility |
bad in water (300 mg l −1 ) |
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safety instructions | |||||||||||||||||||
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MAK |
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Global warming potential |
11547 (based on 100 years) |
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Thermodynamic properties | |||||||||||||||||||
ΔH f 0 |
−477.4 kJ / mol |
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As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
Dichlorodifluoromethane , also R-12 , Freon-12 , is a non-toxic, colorless, incombustible, inert and liquefiable gas . It is heavier than air; in high concentrations it is suffocating.
It was used as a refrigerant and propellant in spray cans until it was banned by the CFC-Halon Prohibition Ordinance . Chemically, it belongs to the group of CFCs (chlorofluorocarbons) or freons. It damages the ozone layer if it gets into the higher atmosphere . R12 was defined as the reference substance for the ozone depletion potential ( ODP ) and therefore has an ODP of 1.
At very high temperatures, certain materials with a large surface (such as aluminum chips, potassium, zinc or magnesium) can also explode.
Extraction and presentation
Dichlorodifluoromethane can be obtained by reacting tetrachloromethane with hydrogen fluoride at 490 ° C and 70 atm, whereby a mixture of trichlorofluoromethane and dichlorodifluoromethane in a ratio of 21:79 is formed. The ratio can be further improved by the presence of antimony (III) chloride and chlorine.
Sodium hexafluorosilicate under pressure at 270 ° C, titanium (IV) fluoride , chlorine trifluoride , cobalt (III) fluoride , iodine pentafluoride and bromine trifluoride are also suitable as fluorinating agents for carbon tetrachloride.
Also, antimony (III) fluoride in the presence of antimony (V) chloride is useful as a fluorinating agent.
The degradation reactions that form dichlorodifluoromethane include chlorinolysis at 550 ° C of 1,1-difluoroethane , which is formed by the reaction of acetylene with hydrogen fluoride, or heating of silver chlorodifluoroacetate with chlorine.
Manufacture and use
The manufacture and use of CFCs, like R-12, was banned in the Montreal Protocol in 1987 because these substances destroy the protective ozone layer. Only emerging countries (e.g. China) were allowed to use it for their own use until 2010. The production quantities of R-12 in China significantly exceeded domestic requirements, and R-12 was also imported into the EU. Import bans were circumvented through false declarations.
Environmental impact
Web links
Individual evidence
- ↑ a b c d e f g h i j k l Entry on dichlorodifluoromethane in the GESTIS substance database of the IFA , accessed on April 16, 2018 (JavaScript required)
- ↑ Schweizerische Unfallversicherungsanstalt (Suva): Limit values - current MAK and BAT values (search for 75-71-8 or dichlorodifluoromethane ), accessed on May 5, 2020.
- ↑ G. Myhre, D. Shindell et al .: Climate Change 2013: The Physical Science Basis . Working Group I contribution to the IPCC Fifth Assessment Report. Ed .: Intergovernmental Panel on Climate Change . 2013, Chapter 8: Anthropogenic and Natural Radiative Forcing, pp. 24-39; Table 8.SM.16 ( PDF ).
- ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-19.
- ↑ Entry on ozone depletion potential. In: Römpp Online . Georg Thieme Verlag, accessed on April 20, 2011.
- ^ A b c Alan R. Katritzky, Thomas L. Gilchrist, Otto Meth-Cohn, Charles Wayne Rees: Comprehensive Organic Functional Group Transformations . Elsevier, 1995, ISBN 978-0-08-042704-1 , pp. 220–225 ( limited preview in Google Book search).
- ^ AA Banks, HJ Emeléus et al. a .: 443. The reaction of bromine trifluoride and iodine pentafluoride with carbon tetrachloride, tetrabromide, and tetraiodide and with tetraiodoethylene. In: J. Chem. Soc. 0, 1948, p. 2188, doi : 10.1039 / JR9480002188 .
- ↑ Jennifer Orme-Zavaleta, Jan Connery: Drinking Water Health Advisory Volatile Organic Compounds . CRC Press, 1990, ISBN 978-0-87371-436-5 , pp. 21 ( limited preview in Google Book search).
- ↑ Eco-Crimes - crime against nature , ARD, 2008.