Tetrachloro-1,2-difluoroethane
Tetrachloro-1,2-difluoroethane is a chlorofluorocarbon known as Freon 112, CFC-112 or R-112. It has a symmetrical structure CCl2FCCl2F and so can be called symmetrical tetrachlorodifluoroethane. "Symmetrical" may also be abbreviated to "s-" or "sym-". In contrast an asymmetrical isomer has formula CCl3CClF2.
Production
CFC-112 can be made in a reaction of hexachloroethane or tetrachloroethane with hydrogen fluoride and extra chlorine. This reaction is catalysed by aluminium fluoride with some extra iron, nickel and chromium at 400°C. The extra metal in the catalyst yields can be 98% compared with the unsymmetrical isomer.Mixed with perfluorooctane, it is a solvent for polydimethylsiloxane.
CFC-112 can be prepared as a mixture with other hydrochlorofluorocarbons from trichloroethylene and anhydrous hydrogen fluoride when electric current is passed through.
When CFC-11 is packaged with alcohol in a metal container, a free radical reaction can result in production of CFC-112.
Properties
Critical properties are critical temperature 278°C, critical pressure 4.83 MPa at a density of 0.754 g/cc.Tetrachloro-1,2-difluoroethane is not flammable.
Tetrachloro-1,2-difluoroethane, like other chlorofluorocarbon compounds reacts violently with sodium, potassium or barium.
Tetrachloro-1,2-difluoroethane is not very toxic, and the lethal dose is estimated at 25 g/kg. It is not carcinogenic.
Use
Tetrachlorodifluoroethane has been used as a veterinary medicine to treat parasites such as liver fluke in sheep.MIL-C-8638 is a military specification for a cleaning solvent that contained tetrachlorodifluoroethane, trichlorotrifluoroethane, and isopropyl alcohol. It was used to clean aircraft oxygen systems.
Tetrachlorodifluoroethane can be used as an intermediate in the manufacture of tetrachloroethylene.