Bromochlorodifluoromethane
Definition and meaning of Bromochlorodifluoromethane in chemistry.
Bromochlorodifluoromethane is a halogenated methane derivative with the formula CBrClF2, better known by its fire-service name Halon 1211 (BCF), historically used as a liquefied-gas fire-suppressing agent in portable extinguishers.
In more detail
The molecule is stored as a compressed liquid that flashes into a dense vapor on release, smothering flames while its carbon-bromine bond homolyzes to release bromine radicals that interrupt the free-radical chain reaction of combustion, making it far more effective per unit mass than inert gases or water. Because it is a bromine- and chlorine-containing haloalkane, it also catalytically destroys stratospheric ozone; its ozone depletion potential (about 3.0, relative to CFC-11 at 1.0) is among the highest of any commercial halocarbon. Consequently, the Montreal Protocol banned new production in developed countries starting in 1994, though existing stocks remain in service for critical uses such as aircraft cabin and engine fire protection.
Key facts
| Formula | CBrClF2 |
|---|---|
| Common name | Halon 1211 (BCF) |
| Molar mass | ~165.4 g/mol |
| Field | Organic Chemistry |
A handheld Halon 1211 streaming extinguisher discharges a clean, non-conductive vapor onto an electrical fire in an aircraft cockpit, extinguishing it without leaving residue on sensitive avionics.
Frequently asked questions
Why was Halon 1211 phased out?
It has one of the highest ozone depletion potentials of any halocarbon and is also a potent greenhouse gas, so the Montreal Protocol banned production of new supplies in developed nations from 1994 onward, though recycled stock is still permitted for essential uses.
How does Halon 1211 put out fires differently than water or CO2?
Rather than mainly cooling or displacing oxygen, it chemically interrupts the combustion chain reaction through bromine radical scavenging, which is why very small amounts can extinguish a fire effectively.