Dichlorodifluoromethane

Structural formula
	Wedge line formula to clarify the geometry
General
Surname	Dichlorodifluoromethane
other names	Difluorodichloromethane; R-12; Freon-12; Friday 12; CFC-12;
Molecular formula	CCl 2 F 2
Brief description	colorless, non-flammable gas with an ethereal odor
External identifiers / databases
EC number	200-893-9
ECHA InfoCard	100,000,813
PubChem	6391
ChemSpider	6151
Wikidata	Q423021
properties
Molar mass	120.91 g mol −1
Physical state	gaseous
density	5.5488 kg m −3 (0 ° C, 1013 mbar) ; 1.488 kg l −1 (liquid at boiling point) ;
Melting point	−157.78 ° C
boiling point	−29.8 ° C
Vapor pressure	5.7 bar (20 ° C); 7.5 bar (30 ° C); 12.2 bar (50 ° C);
solubility	bad in water (300 mg l −1 )
safety instructions
H and P phrases	H: 280-420-412
	P: 273-501
MAK	DFG : 1000 ml · m -3 or 5000 mg · m -3 ; Switzerland: 1000 ml · m -3 or 5000 mg · m -3 ;
Global warming potential	11547 (based on 100 years)
Thermodynamic properties
ΔH f 0	−477.4 kJ / mol
	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.

{\ displaystyle {\ ce {CCl4 + HF -> CCl3F + CCl2F2}}}

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.

{\ displaystyle {\ ce {CCl4 + Na2SiF6 -> CCl3F + CCl2F2 + CCl3F + NaCl + SiF4}}}

{\ displaystyle {\ ce {CCl4 + BrF3 -> BrF + CCl2F2 + CCl3F}}}

Also, antimony (III) fluoride in the presence of antimony (V) chloride is useful as a fluorinating agent.

{\ displaystyle {\ ce {2 CCl4 + SbF3 -> CCl2F2 + CCl3F}}}

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.

{\ displaystyle {\ ce {CClF2CO2Ag + Cl2 -> CCl2F2 + CO2 + AgCl}}}

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

Concentration in the atmosphere over time
Concentration (nmol / m³) at sea level of R-12 (measured in the 1990s)

Web links

Commons : Dichlorodifluoromethane - Collection of pictures, videos and audio files

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.

[GESTIS-1] ↑ ^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)

[2] Schweizerische Unfallversicherungsanstalt (Suva): Limit values - current MAK and BAT values (search for 75-71-8 or dichlorodifluoromethane ), accessed on May 5, 2020.

[3] 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 ).

[CRC90_5_19-4] 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.

[5] Entry on ozone depletion potential. In: Römpp Online . Georg Thieme Verlag, accessed on April 20, 2011.

[Alan_R._Katritzky,_Thomas_L._Gilchrist,_Otto_Meth-Cohn,_Charles_Wayne_Rees-6] 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).

[DOI10.1039/JR9480002188-7] 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-8] 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).

[9] Eco-Crimes - crime against nature , ARD, 2008.