Preparation of tetrafluoroethylene from the pyrolysis of pentafluoropropionate salts

Abstract

The use of tetrafluoroethylene (TFE) in academic institutions beyond a few millimoles has often been inhibited by the compound's inherent danger and general lack of commercial availability. On the other hand, TFE is prepared industrially on a rather large scale by a number of major fluorochemical companies via the pyrolysis of chlorodifluoromethane at high temperatures, yielding TFE and HCl. For a few years at The University of Alabama and Clemson University, we have been preparing TFE on a 100 +-gram scale by the pyrolysis under dynamic vacuum of pentafluoropropionate salts, which can be obtained from the neutralization of pentafluoropropionic acid with a M(OH) n (where M = Li, Na, K, and Cs for n = 1 and Mg, Ca, and Ba for n = 2). Additionally, potassium pentafluoropropionate can be prepared from the reaction of potassium trimethylsilanolate and ethyl pentafluoropropionate. The pentafluoropropionate salts and their

TMSCF3 as a Convenient Source of CF2=CF2 for Pentafluoroethylation, (Aryloxy)tetrafluoroethylation, and Tetrafluoroethylation

“…Tetrafluoroethylene (TFE, CF 2 =CF 2 ), as a bulk fluorochemical for the industrial manufacture of poly(tetrafluoroethylene) and copolymers with other alkenes, is an ideal C2 building block for incorporating fluorinated moieties such as ‐CF 2 CF 2 ‐, HCF 2 CF 2 ‐, and CF 2 =CF‐ into small molecules . However, TFE is suspected to be carcinogenic, unstable towards radicals, and prone to explode when in contact with air, all of which in turn require that TFE gas is handled with extreme caution, including during storage and transport …”

“…To overcome the inherent limitations associated with using TFE gas in academic laboratories, several TFE precursors have been developed that release TFE gas on site in small amounts. Available methods include the reduction of 1,2‐dihalotetrafluoroethanes (XCF 2 CF 2 Y; X, Y=Br, Cl) with zinc powder and the pyrolysis of sodium perfluoropropionate or poly(tetrafluoroethylene) at high temperatures. However, the restricted availability of XCF 2 CF 2 Y and the harsh conditions required for the pyrolysis reactions have limited the utilizations of these methods, thus preventing the development of fluoroalkylation reactions with TFE in common research laboratories.…”

Advances in the Synthesis and Application of Tetrafluoroethylene‐ and 1,1,2,2‐Tetrafluoroethyl‐Containing Compounds

“…As TFE is a suspected carcinogene, it may undergo explosive polymerization in the liquid state and its mixture with air is explosive; careful handling is thus essential. In industry, TFE is produced by pyrolysis of chlorodifluoromethane, which is impractical for smaller scale laboratory preparation . Commercial availability of this gas for chemical research is very low.…”

“…For all those reasons, several methods for the laboratory preparation of TFE on a small scale have been developed, such as reduction of 1,2‐dibromotetrafluoroethane with zinc powder in EtOH and pyrolysis of poly(tetrafluorethylene) (Scheme ) . Equimolar TFE/CO 2 mixture was prepared by pyrolysis of potassium pentafluoropropionate . Very recently, 2:1 mixture of Me 3 SiF/TFE was produced by dimerization of difluorocarbene produced by decomposition of CF 3 SiMe 3 , also known as the Ruppert–Prakash reagent (Scheme ) …”

Modular and Processable Fluoropolymers Prepared via a Safe, Mild, Iodo–Ene Polymerization

“…A final challenge of fluoropolymer research is the safety of the fluorinated ethylene monomers. Tetrafluoroethylene (TFE) is explosive on contact with organic compounds, 24 limiting its academic use 25−27 and making copolymers such as ETFE ( 5 ) especially dangerous to produce. Additionally, many of the fluoropolymers are prepared via emulsion polymerization, which requires fluorosurfactants that are prone to bioaccumulation.…”