Dichlorofluoromethane or Freon 21 or R 21 is a
halomethane or
hydrochlorofluorocarbon
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and pr ...
with the formula CHCl
2F. It is a colorless and odorless gas. It is produced by fluorination of
chloroform using a catalyst such as
antimony trifluoride
Antimony trifluoride is the inorganic compound with the formula SbF3. Sometimes called Swarts' reagent, is one of two principal fluorides of antimony, the other being SbF5. It appears as a white solid. As well as some industrial applications, i ...
:
[
:CHCl3 + HF → CHCl2F + HCl
]
Uses
Dichlorofluoromethane was used as a propellant and refrigerant. Due to its role in ozone depletion, dichlorofluoromethane has been largely phased out. It has ozone depletion potential
The ozone depletion potential (ODP) of a chemical compound is the relative amount of degradation to the ozone layer it can cause, with trichlorofluoromethane (R-11 or CFC-11) being fixed at an ODP of 1.0. Chlorodifluoromethane (R-22), for exampl ...
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
The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. It was agreed on 16 September 1987, and entered into force o ...
.
Pyrolysis of a mixture of dichlorofluoromethane and chlorofluoromethane gives hexafluorobenzene
Hexafluorobenzene, HFB, , or perfluorobenzene is an organic, aromatic compound. In this derivative of benzene all hydrogen atoms have been replaced by fluorine atoms. The technical uses of the compound are limited, although it is recommended as ...
:
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
In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it uncha ...
Pbca.
Safety
Its toxicity is comparable to that of chloroform. Its TLV is 10ppm.[
]
References
External links
*
*
Termochemistry data at chemnet.ru
Entry at Air Gas Liquide Encyclopaedia
{{Halomethanes
Hydrochlorofluorocarbons
Halomethanes
Refrigerants
Propellants