Tetrafluoroethylene

Tetrafluoroethylene (TFE) is a chemical compound composed containing only carbon and fluorine with the molecular formula C2F4. This gaseous species is used primarily in the industrial preparation of polymers. In organic chemistry, tetrafluoroethylene is a potent dienophile.

Properties
TFE is a derivative of ethylene in which each of the four hydrogen atoms have been replaced with fluorine. Tetrafluoroethylene is a colourless, odourless gas. Like all unsaturated fluorocarbons it is susceptible to nucleophilic attack. In air it is prone to form explosive peroxides.

Industrial use
Polymerization of tetrafluoroethylene produces polytetrafluoroethylene (PTFE) polymers such as Teflon. PTFE is one of the three fluorocarbon resins composed wholly of fluorine and carbon. The other resins in this group are perfluoroalkoxy resin (PFA) and fluorinated ethylene propylene (FEP). TFE is also used in the preparation of copolymers such as ETFE.

Manufacture
TFE is manufactured from chloroform. Chloroform is fluorinated by reaction with hydrogen fluoride to produce chlorodifluoromethane (R-22). Pyrolysis of chlorodifluoromethane then yields TFE.
 * CHCl3 + 2 HF → CHClF2 + 2 HCl
 * 2 CHClF2 → C2F4 + 2 HCl

A laboratory synthesis entails pyrolysis of a PTFE under a vacuum. The PTFE polymer "cracks" and depending on the pressure, produces mainly C2F4.

Safety
LD50(rat, inhalation) = 40000 ppm.