Chlorodifluoromethane
Definition and meaning of Chlorodifluoromethane in chemistry.
Chlorodifluoromethane is a colorless, virtually odorless haloalkane gas with the formula CHClF2, better known by its refrigerant designation R-22 or industrial code HCFC-22. It is produced industrially by reacting chloroform with hydrogen fluoride in the presence of an antimony pentachloride catalyst.
In more detail
As a hydrochlorofluorocarbon (HCFC), it contains hydrogen, chlorine, and fluorine bonded to a single carbon, giving it favorable thermodynamic properties for heat transfer along with residual chlorine that can catalyze stratospheric ozone destruction. For decades it was the dominant refrigerant in home and commercial air conditioning, but the Montreal Protocol classifies it as an ozone-depleting substance, so its production and use are being phased out worldwide in favor of HFCs and other non-chlorine alternatives. It is also an important industrial feedstock, since pyrolysis of CHClF2 at high temperature yields tetrafluoroethylene, the monomer used to make polytetrafluoroethylene (Teflon).
Key facts
| Formula | CHClF2 |
|---|---|
| Field | Organic Chemistry |
| Common name | R-22 / HCFC-22 |
| Boiling point | -40.8 °C |
Heating chlorodifluoromethane to about 600-800°C causes two molecules to lose HCl and combine, forming tetrafluoroethylene (C2F4), the starting material for PTFE production.
Frequently asked questions
Why is R-22 being phased out?
Its chlorine atom contributes to catalytic destruction of stratospheric ozone, so the Montreal Protocol schedules HCFCs like R-22 for phase-out in favor of chlorine-free refrigerants such as R-410A.
Is chlorodifluoromethane the same as Freon?
Freon is a trademarked brand name historically applied to various chlorofluorocarbon and hydrochlorofluorocarbon refrigerants, including CHClF2, which is marketed as Freon 22 or R-22.