Dichlorofluoromethane or Freon 21 or R 21 is a

halomethane Halomethane compounds are derivatives of methane () with one or more of the hydrogen atoms replaced with halogen atoms ( F, Cl, Br, or I). Halomethanes are both naturally occurring, especially in marine environments, and human-made, most notably ...

or hydrochlorofluorocarbon with the formula CHCl₂F. It is a colorless and odorless gas. It is produced by fluorination of

chloroform Chloroform, or trichloromethane, is an organic compound with chemical formula, formula Carbon, CHydrogen, HChlorine, Cl3 and a common organic solvent. It is a colorless, strong-smelling, dense liquid produced on a large scale as a precursor to ...

using a catalyst such as antimony trifluoride: :CHCl₃ + HF → CHCl₂F + HCl

Uses

Dichlorofluoromethane was used as a

propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...

and refrigerant. Due to its role in

ozone depletion Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone l ...

, dichlorofluoromethane has been largely phased out. It has ozone depletion potential 0.04. Production and consumption has been since 2004 reduced to 15% of level from 1989 and it is to be phased out in 2015 according to Montreal Protocol. Pyrolysis of a mixture of dichlorofluoromethane and chlorofluoromethane gives hexafluorobenzene: :3 CHCl₂F + 3 CH₂ClF → C₆F₆ + 9 HCl

Additional physical data

Its critical point is at 178.5 °C (451.7K) and 5.17MPa (51.7bar). At temperatures from 5K to 105K, it has one phase in the space group Pbca.

Safety

Its toxicity is comparable to that of

. Its TLV is 10ppm.

References

External links

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Termochemistry data at chemnet.ru

Entry at Air Gas Liquide Encyclopaedia
{{Halomethanes Hydrochlorofluorocarbons Halomethanes Refrigerants Propellants